Source: IOWA STATE UNIVERSITY submitted to
ECOLOGY AND MANAGEMENT OF EUROPEAN CORN BORER AND OTHER LEPIDOPTERAN PESTS OF CORN
Sponsoring Institution
National Institute of Food and Agriculture
Project Status
COMPLETE
Funding Source
HATCH
Reporting Frequency
Annual
Accession No.
0153918
Grant No.
(N/A)
Cumulative Award Amt.
(N/A)
Proposal No.
(N/A)
Multistate No.
NC-205
Project Start Date
Oct 1, 2010
Project End Date
Sep 30, 2015
Grant Year
(N/A)
Program Code
[(N/A)]- (N/A)
Project Director
Gassmann, AA, JO.
Recipient Organization
IOWA STATE UNIVERSITY
2229 Lincoln Way
AMES,IA 50011
Performing Department
Entomology
Non Technical Summary
Bt corn is widely used to manage European corn borer (ECB). The durability of this technology will be lost if ECB develops Bt resistance. Fitness costs, which are defined as lower fitness (e.g, survival or fecundity) for Bt-resistant insects when in the absence of Bt, will act to delay resistance. Thus, accurately quantifying fitness costs of Bt resistance is essential to predict the long-term durability of Bt corn for controlling ECB. We will use laboratory-selected strains of ECB that are resistant to Bt to test fitness cost of Bt resistance. Insects will be raised on corn plants, rather than artificial diet, to more closely mirror conditions in the field. Data will provide guidance to regulatory agencies including the US EPA for how to best manage the threat of Bt resistance in ECB.
Animal Health Component
(N/A)
Research Effort Categories
Basic
(N/A)
Applied
(N/A)
Developmental
(N/A)
Classification

Knowledge Area (KA)Subject of Investigation (SOI)Field of Science (FOS)Percent
2111510113050%
2113110113050%
Knowledge Area
211 - Insects, Mites, and Other Arthropods Affecting Plants;

Subject Of Investigation
1510 - Corn; 3110 - Insects;

Field Of Science
1130 - Entomology and acarology;
Goals / Objectives
1. Investigate the relationship between transgenic maize and the agricultural environment. 2. Adapt IPM systems for the changing pest complexes in maize. 3. Investigate ecology, evolution, genetics, and behavior of pest Lepidoptera. 4. Employ electronic delivery methods to disseminate information related to sustainable management of Lepidopteran pests.
Project Methods
We will use the two Bt-resistant strains, one with resistance to Cry1F and another with resistance to Cry1Ab, and an accompanying susceptible strain. Both resistant strains will contain resistance alleles derived from the field. Two complimentary experiments will be conducted to measure fitness costs: 1) life-history based measurement of fitness costs for larvae reared on corn and 2) selection experiment using insects reared on corn. Measurements of fitness costs will be made using two corn varieties to better understand the variability in costs that might arise in the field. While measurements of life-history characters will allow us to quantify dominance of costs and which traits are affected, the selection experiment will provide a holistic measurement of costs and will provide the best overall estimate of the magnitude of fitness costs. Measurements of fitness costs will be made with two widely used commercial non-Bt varieties. Crossing design that will be carried out with Cry1Ab-resistant and susceptible strains to generate heterozygous progeny. A similar design will be used with the Cry1F-resistant and susceptible strains. To test for difference in fitness among genotypic classes, data for each trait will be analyzed with a two-way, mixed model analysis of variance (Proc Mixed in SAS), which will have the fixed factors of genotypic class, corn hybrid, and their interaction; and the random factors of block and its interactions (e.g., block *corn hybrid). A significant effect of genotype or an interaction between genotype by corn hybrid will indicate that fitness differed among the classes of genotype either consistently (significant effect of genotype only) or to varying degrees depending on the corn hybrid (significant genotype by corn hybrid interaction). We propose to conduct several one-generation selection experiments. Each pair of strains (e.g., Cry1Ab-resistant and susceptible) will be crossed to generate a hybrid strain. Neonates from the F2 will be used to infest non-Bt R1 corn plants (corn plants with newly formed ears) and a subsample of larvae will be used in diet bioassays to measure resistance allele frequency in the population. Bioassays will be conducted using Bt toxin at a diagnostic concentration incorporated into diet, as has been done previously in this system. Change in resistance-allele frequency will quantify the intensity of selection against Bt-resistance, which will be tested against the null hypothesis, change in resistance allele frequency = 0, using a one-tailed t-test. We expect that fitness costs will be present when ECB reared on corn plants and that some costs will be non-recessive. Additionally, for some of the life-history traits there will be a significant interaction between corn hybrid and genotype, and pairwise comparisons will demonstrate that costs became greater or more dominant on one of the hybrids. For selection experiments, we expect to observe a significant decline in r alleles when insects are reared on corn plants.

Progress 10/01/10 to 09/30/15

Outputs
Target Audience:The target audience included agricultural companies, biotechnology companies, extension specialists, farmers, members of the scientific community, regional agronomists, regulators, and the general public. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided? Nothing Reported How have the results been disseminated to communities of interest?These results have been communicated to growers, regulatory scientists, industry scientists, government scientists and academics at multiple meetings and workshops and through peer-reviewed publications and popular articles. What do you plan to do during the next reporting period to accomplish the goals? Nothing Reported

Impacts
What was accomplished under these goals? Maize genetically engineered to produce toxins from the bacterium Bacillus thuringiensis (BT) has revolutionized management of European corn borer, corn earworm, fall armyworm and western bean cutworm. For U.S. maize growers, it is estimated that these pests impose over two billion dollars annually in costs associated with management and yield reductions. Effective management of all these pests, however, is threatened by insect resistance to Bt maize. Research conducted under this project is aimed at developing sustainable management of these lepidopteran pests by understanding fundamental aspects of their ecology and genetics, and by developing insect resistance management and integrated pest management strategies. Our goal is to provide growers with up-to-date information for managing these pests. This report summarizes results of studies conducted on lepidopteran pests of maize by scientists from Iowa State University and USDA-ARS Corn Insects & Crop Genetics Research Unit. These results have been communicated to growers, regulatory scientists, industry scientists, government scientists and academics at multiple meetings and workshops and through peer-reviewed publications and popular articles. Objective 1. Investigate the relationship between transgenic maize and the agricultural environment. Selection produced European corn borer larvae that rapidly leave or stay on maize plants. These studies provide a basis for understanding the molecular biology that governs movement behavior in European corn borer larvae and how it may be impacted by pesticide exposure and transgenic maize. A collaborative effort led to the development of a new adaptive resistance management strategy for slowing and mitigating pest resistance to Bt maize. The solution recognizes that it is not too late to implement changes in the insect resistance management strategy to preserve the utility of Bt maize by targeting local management earlier in a sequence of responses to the evolution of resistance, developing area-wide criteria to address widespread product failures, and developing programs to counteract economic forces contributing to rapid resistance evolution. These recommendations for growers and regulators should prolong the life of existing and future transgenic technologies targeting insect pests. Objective 2. Adapt IPM systems for the changing pest complexes in maize. The western bean cutworm, Striacosta albicosta, is a pest of dry beans and maize that recently spread out of the Great Plains to cause economic damage in several parts of the North Central U.S. The first protocols to rear western bean cutworm in the laboratory for multiple generations were developed. Rearing procedures were adapted for Bt toxin diet-overlay assays, and reported the high tolerance of this insect to Cry1 F toxins. The ability to mass produce this pest insect enhances fundamental research, including evaluation of control tactics and toxin susceptibility. The beet webworm, Loxostege sticticalis, is a cosmopolitan pest of maize and forage crops, which migrates northward each growing season from overwintering areas in the south, making their appearance and severity difficult to predict. Collaborative flight mill studies showed that migratory flight synchronizes egg-laying by colonizing females over a short time, contributing to high larval densities and severity of outbreaks. This newly discovered phenomenon is likely common in other migratory moth pests, and will help efforts to better predict infestations. The overall impact of the accomplishments is that growers will have multiple protection options for managing insect pests of maize. Objective 3. Investigate ecology, evolution, genetics, and behavior of pest Lepidoptera. DNA markers and independent estimates of population density were used to reveal that 15% of European corn borer moths disperse > 12 km/generation. Genetic variation in two circadian rhythm genes was linked to differences in generation number (voltinism). Genome regions responsible for resistance to Bt Cry1F and Cry1Ab toxins were identified through application of high throughput genomic markers. These results are important for understanding the evolution and spread of Bt resistance in corn borer populations. Three single locus genetic markers were developed and validated which differentiate E and Z pheromone races of European corn borer. These single-nucleotide polymorphism (SNP) markers are located in the pheromone gland fatty-acyl reductase (pgfar) gene. These genetic markers are the first tools to allow rapid identification of the pheromone race of European corn borer moths, and are an important development for population genetics and ecological research of this insect. Studies on the dispersal of older larvae (late instars) of European corn borer on vegetative maize show that under high density conditions larvae will disperse during each of the five instars. Most of the dispersal occurs with first instars and appears to be density independent for these young larvae, while high dispersal percentages also were found for older larvae, particularly fourth and fifth instars. These results are critical to predicting resistance evolution to Bt maize in fields where the non-Bt refuge seed is mixed in the bag for planting. Sequencing-by-synthesis technology for this insect was employed as part of a novel strategy to develop 71 genetic markers to help researchers study dispersal and other aspects population biology for European corn borer. The new method demonstrates the power of applying sequencing technologies to develop genetic markers in previously under-studied species, regardless of whether it is an insect or any other kind of organism. Objective 4. Employ electronic delivery methods to disseminate information related to sustainable management of Lepidopteran pests. An electronic guide to management of European corn borer was published and made available electronically. This work represents a collaboration among numerous scientists from USDA ARS and Land-Grant Institutions. This work is designed to be accessible to farmers and crop consultants. The European corn borer significantly affects production of maize, as well as other crops, including sorghum, cotton, and many vegetables. For all crops combined, it costs farmers in the United States over 1 billion dollars annually which is attributed to yield losses and cost of control. By the end of the 20th century in most areas heavily populated by European corn borer, corn hybrids withstood the feeding damage of this insect and average yield losses dropped to five or six percent or less. With the introduction of transgenic Bt maize hybrids in the mid-1990s, losses due to European corn borer in fields containing the genetically modified products have now been completely eliminated. However, the major challenge for scientists and practitioners today is to manage the maize-growing systems in North America in a manner that prevents European corn borer from developing populations counter-resistant to genetically modified maize. Management considerations must go beyond this insect and include other maize pests as part of the big picture as well as include factors affecting our environment. The purpose of this publication is to provide a general understanding about the life of the European corn borer, its management as it relates to a maize growing system and other crops vulnerable to losses caused by this insect, and what steps a practitioner can take to prevent or minimize problems in the future.

Publications

  • Type: Journal Articles Status: Published Year Published: 2015 Citation: Andow, D. A., S. G. Pueppke, A. W. Schaafsma, A. J. Gassmann, T. W. Sappington, L. J. Meinke, P. D. Mitchell, T. M. Hurley, R. L. Hellmich, and R. P. Porter. 2015. Forum: Early detection and mitigation of resistance to Bt maize by western corn rootworm (Coleoptera: Chrysomelidae). J. Econ. Entomol. (DOI: 10.1093/jee/tov238 early access 9/11/15; accepted 7/17/15).
  • Type: Books Status: Awaiting Publication Year Published: 2016 Citation: Mason, CE, ME Rice, TW Sappington, TE Hunt, RP Porter, RL Hellmich, TS Baut�, DA Andow, CD DiFonzo, GD Buntin, GP Dively, WD Hutchison, C Nansen, JJ Knodel, DD Calvin, EM Cullen, GB Cronholm, F Huang, LL Buschman, JW Van Duyn, WB Showers, JF Witkowski, RA Higgins, DW Onstad. 2016. European corn borer ecology and management and its interaction with other Lepidoptera pests of corn. No. Cent. Reg. Ext. Publ. 327. Iowa State University, Ames, IA.
  • Type: Journal Articles Status: Published Year Published: 2014 Citation: Coates, B.S. and C.A. Abel. 2014. The mitochondrial genome of the American lotus borer, Ostrinia penitalis (Lepidoptera: Crambidae). Mitochondrial DNA DOI: 10.3109/19401736.2014.971296.
  • Type: Journal Articles Status: Published Year Published: 2015 Citation: Levy, R.C., Kozak, G.M., Wadsworth, C.B., Coates, B.S., Dopman, E.B. 2015. Explaining the sawtooth: Latitudinal periodicity in a circadian gene correlates with shifts in generation number. Journal of Evolutionary Biology 28:40-53.
  • Type: Journal Articles Status: Published Year Published: 2015 Citation: Nagoshi, R.N., Rosas-Garcia, N.M., Meagher Jr, R.L., Fleischer, S.J., Westbrook, J.K., Sappington, T.W., Hay-Roe, M., Gruters Thomas, J.M., Murua, G.M. 2015. Haplotype profile comparisons between Spodoptera frugiperda (Lepidoptera:Noctuidae) populations from Mexico with those from Puerto Rico, South America, and the United States and their implications for migratory behavior. Journal of Economic Entomology 108:135-144.
  • Type: Journal Articles Status: Published Year Published: 2015 Citation: Pan, H., Yang, X., Bidne, K., Hellmich, R. L., Siegfried, B. D., & Zhou, X. (2015). Selection of Reference Genes for RT-qPCR Analysis in the Monarch Butterfly, Danaus plexippus (L.), a Migrating Bio-Indicator. PloS one 10(6):e0129482.
  • Type: Journal Articles Status: Published Year Published: 2015 Citation: Su, H., Tian, J., Naranjo, S.E., Romeis, J., Hellmich Ii, R.L., Shelton, A.M. 2015. Bt plants expressing Cry1Ac, Cry2Ab and Cry1F do not harm the assassin bug, Zelus renardii (Kolenati (Hemiptera: Reduviidae). Environmental Toxicology and Chemistry 139:23-30.
  • Type: Journal Articles Status: Published Year Published: 2015 Citation: Zhang, T.T., Coates, B.S., Ge, X., Bai, S., He, K., Wang, Z. 2015. Male- and female-biased gene expression of olfactory related genes in the antennae of the Asian corn borer (Guen�e) (Lepidoptera: Crambidae). PLoS One 10:e0128550.
  • Type: Journal Articles Status: Published Year Published: 2015 Citation: Kuhlmann, U., Sappington, T.W., Wang, Z. 2015. Editorial: Special issue highlighting research presented at the 25th IWGO Conference, Chicago 2014. Journal of Applied Entomology 139:401-402.
  • Type: Journal Articles Status: Published Year Published: 2015 Citation: Binning, R. R., Coats, J., Kong, X., & Hellmich, R. L. (2015). Susceptibility to Bt proteins is not required for Agrotis ipsilon aversion to Bt maize. Pest management science 71:601-606.
  • Type: Journal Articles Status: Published Year Published: 2015 Citation: Coates, B.S., Siegfried, B.D. 2015. Linkage of an ABC transporter to a single QTL that controls Ostrinia nubilalis larval resistance to the Bacillus thuringiensis Cry1Fa toxin. Insect Biochemistry and Molecular Biology 63:86-96.
  • Type: Journal Articles Status: Published Year Published: 2015 Citation: Zhang, L., Pan, P., Sappington, T.W., Lu, W., Luo, L., Jiang, X. 2015. Accelerated and synchronized oviposition induced by flight of young females may intensify larval outbreaks of the rice leaf roller. PLoS One 10:e0121821.
  • Type: Journal Articles Status: Published Year Published: 2015 Citation: Coates, B.S. 2015. Horizontal transfer of a non-autonomous Helitron among insect and viral genomes. Biomed Central (BMC) Genomics 16:137.


Progress 10/01/13 to 09/30/14

Outputs
Target Audience: The target audience included agricultural companies, biotechnology companies, extension specialists, farmers, members of the scientific community, regional agronomists, regulators, and the general public. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided? All participants (especially students) gained valuable research experience by conducting this research. How have the results been disseminated to communities of interest? These results have been communicated to growers, regulatory scientists, industry scientists, government scientists and academics at multiple meetings and workshops and through peer-reviewed publications and popular articles. What do you plan to do during the next reporting period to accomplish the goals? Quantitative trait locus (QTL) mapping in European corn borer (ECB) has previously identified a single major locus which strongly influences the inheritance of Cry1Fa resistance, and two independently segregating QTL that determine Cry1Ab resistance. Additional segregating molecular genetic markers will be in ECB pedigrees with the goal of increasing resolution within these QTL regions and thereby reducing the physical size of the genome region encoding resistance gene(s). Additional experiments will be conducted related to larval movement, moth migratory flight and European corn borer genomics.

Impacts
What was accomplished under these goals? Corn genetically engineered to produce toxins from the bacterium Bacillus thuringiensis (BT) has revolutionized management of European corn borer, corn earworm, fall armyworm and western bean cutworm. For U.S. corn growers, it is estimated that these pests impose over two billion dollars annually in costs associated with management and yield reductions. Effective management of all these pests, however, is threatened by insect resistance to Bt maize. Research conducted under this project is aimed at developing sustainable management of these lepidopteran pests by understanding fundamental aspects of their ecology and genetics, and by developing insect resistance management and integrated pest management strategies. Our goal is to provide growers with up-to-date information for managing these pests. This report summarizes results of studies conducted on lepidopteran pests of maize by scientists from Iowa State University and USDA-ARS Corn Insects & Crop Genetics Research Unit. These results have been communicated to growers, regulatory scientists, industry scientists, government scientists and academics at multiple meetings and workshops and through peer-reviewed publications and popular articles. A full midgut transcriptome was assembled for European corn borer by using Next Generation Sequence data. Subsequent estimates of gene expression from RNA-seq experiments demonstrated that gene transcription among Cry1Fa resistant larvae are highly similar to non-resistant larvae. These results suggested that resistance is constitutive and blocks the mode of action from Bt toxin. A series of studies were conducted in collaboration with researchers from Cornell University and Agroscope in Switzerland to address major concerns of regulatory agencies about Bt crops: the evolution of pest resistance to Bt and the effects of Bt crops on important natural enemies that suppress lepidopteran pest populations. These studies indicate that important natural enemies are not harmed by the commonly used Cry proteins in Bt crops and that these natural enemies can, in turn, reduce the evolution of resistance in the pest species. An initiative has been launched by the International Organization of Biological Control (IOBC) to develop a generic and scientifically rigorous approach to evaluate potential risks of Bt crops on non-target arthropods (insects and spiders). This has resulted in a series of publications to provide guidance to countries that are currently developing risk assessment guidelines and to help harmonize regulatory requirements in different regions of the world. This approach will help guide the development of standardized laboratory protocols for testing Bt-crop derived stressors on non-target arthropods. Behaviors of insects, including movement and mating, are important factors that can influence how fast resistance to Bt crops develops in the field. This is a particularly important question now because blended-refuge (i.e., mixed Bt and non-Bt seeds) approaches to insect resistance management are being considered and implemented. A series of studies were conducted with lepidopteran pests of corn to assess how larval behavior may compromise the high-dose/refuge strategy. When European corn borer larvae from a colony selected for Cry1Ab resistance were exposed to diet with Cry1Ab toxin, they did not show a greater ability to avoid toxins (called "behavioral resistance") than did susceptible larvae. Fall armyworm larvae demonstrated an initial, post-ingestive aversive response to Cry1F corn, and very few larvae survived a 14-day exposure, which should mitigate selection for resistance. Also, black cutworm larval aversion to Cry1F toxin suggests these insects will abandon Cry1F corn in the field before any selection for resistance. This information will be incorporated into a model and to guide recommendations for new types of refuges for managing pest resistance to Bt corn. One possibility is increased use of blended seed refuges, which would be easier for growers to implement than current insect resistance management practices. The fall armyworm, Spodoptera frugiperda, is a long-distance migratory moth pest of corn. Four widely separated populations in Mexico were examined for variation in mitochondrial DNA (mtDNA) haplotype and compared to other locations. The Mexico populations were similar in genetic profile to those from Texas and South America, and distinct from those of Florida and Puerto Rico. These data extend the mtDNA haplotype distribution map in the Western Hemisphere and confirms that the previously observed regional differences in haplotype frequencies are stable over time. The Mexico collections were associated with haplotypes rarely found elsewhere, suggesting that migratory interactions with foreign populations, including those neighboring Texas, may be limited. Understanding the migration patterns of fall armyworm will facilitate efforts to predict the spread of pesticide resistance traits that repeatedly arise in this species and assess the consequences of changing climatic trends on the geographic range of infestation.

Publications

  • Type: Journal Articles Status: Published Year Published: 2014 Citation: Agunbiade TA, Coates BS, Dantinon B, Djouaka R, Tsai MR, Sun W, Tamo M, Pittendrigh BR. 2014. Genetic Differentiation among Maruca vitrata F. (Lepidoptera: Crambidae) Populations on Cultivated Cowpea and Wild Host Plants: Implications for Insect Resistance Management and Biological Control Strategies. PLoS ONE 9(3):e92072.
  • Type: Journal Articles Status: Published Year Published: 2014 Citation: Petzold-Maxwell JL, Siegfried BD, Hellmich RL, Abel CA, Coates BS, Spencer TA, Gassmann AJ. 2014. Affects of maize lines on fitness costs of Cry1F resistance in the European corn borer. Journal of Economic Entomology 107(2):764-772.
  • Type: Journal Articles Status: Published Year Published: 2014 Citation: Li J, Coates BS, Kim KS, Bourguet D, Ponsard S, He K, Wang Z. 2014. The genetic structure of Asian corn borer, Ostrinia furnacalis, populations in China: Haplotype variance in Northern populations and potential impact on management of resistance to transgenic maize. Journal of Heredity 105(5)642-655.
  • Type: Journal Articles Status: Published Year Published: 2014 Citation: Steele LD, Muir WM, Rangesa M, Seong KM, Quiros CC, Clark JM, Coates BS, Pittendrigh BR. 2014. Genome-wide sequencing and an open reading frame analysis of DDT susceptible (91-C) and resistant (91-R) Drosophila melanogaster laboratory populations. PLoS One 9(6):e98584.
  • Type: Journal Articles Status: Published Year Published: 2014 Citation: Sappington, T. W., and C. S. Burks. 2014. Patterns of flight behavior and capacity of unmated navel orangeworm (Lepidoptera: Pyralidae) adults related to age, gender, and wing size. Envrionmental Entomology 43(3):696-705.
  • Type: Journal Articles Status: Published Year Published: 2013 Citation: Kim, K. S., and T. W. Sappington. 2013. Population genetics strategies to characterize long-distance dispersal of insects. J. Asia-Pac. Entomol. 16(1):87-97.
  • Type: Book Chapters Status: Published Year Published: 2014 Citation: Sappington, T.W. 2014. Emerging issues in Integrated Pest Management implementation and adoption in the North Central USA. Pp. 65-97. In: R. Peshin, and D. Pimental (eds.), Integrated Pest Management  Experiences with Implementation, Global Overview, Vol. 4. Springer Science+Business Media, Dordrecht.


Progress 01/01/13 to 09/30/13

Outputs
Target Audience: This research targets scientists and regulators interested in managing insect resistance to Bt corn, improving non-target evaluations of GM crops or both. Also this research targets corn growers interested in integrated management approaches to control insect pests of corn. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided? Participants in this research included one postdoctoral scientist, two graduate students, three technicians and several undergraduates. All participants gained valuable research experience by conducting this research. How have the results been disseminated to communities of interest? These results have been communicated to growers, regulatory scientists, industry scientists, government scientists and academics at multiple meetings and workshops and through peer-reviewed publications and popular articles. What do you plan to do during the next reporting period to accomplish the goals? Additional experiments will be conducted related to larval movement, moth migratory flight and European corn borer genomics.

Impacts
What was accomplished under these goals? Maize genetically engineered to produce toxins from the bacterium Bacillus thuringiensis (BT) has revolutionized management of European corn borer, corn earworm, fall armyworm and western bean cutworm. For U.S. corn growers, it is estimated that these pests impose over two billion dollars annually in costs associated with control and yield reductions. Effective management of all these pests, however, is threatened by insect resistance to Bt maize. Research conducted under this CRIS is aimed at developing sustainable management of these Lepidopteran pests by understanding fundamental aspects of the ecology and genetics, and by developing insect resistance management and integrated pest management strategies. Our goal is to provide growers with up-to-date information for managing these pests. This report summarizes results of studies conducted on Lepidopteran pests of maize by scientists from Iowa State University and USDA-ARS Corn Insects & Crop Genetics Research Unit. These results have been communicated to growers, regulatory scientists, industry scientists, government scientists and academics at multiple meetings and workshops and through peer-reviewed publications and popular articles. Part of this research was funded by USDA NIFA through Biotechnology Risk Assessments Grants (BRAG) and Agriculture and Food Research Initiative (AFRI) grants. Laboratory rearing of the western bean cutworm, an important maize pest, eluded scientists for many years, until a paper reported here described procedures to successfully rear this insect for multiple generations in the laboratory. This new rearing procedure was used to obtain the first reported data regarding susceptibility of western bean cutworm to Bt toxins in dose-response bioassays. This work was highlighted in an Entomological Society of America Press Release. This work will enhance fundamental research and allow scientists to conduct field evaluations of new control tactics. Molds are common contaminants of maize that can occur in all parts of the plant. In particular, an ear mold called Fusarium verticillioides is an important disease in maize because of detrimental impacts on plant health that result in economic losses from reductions in yield and grain quality. Also, consumption of mold toxins in infected kernels, primarily fumonisins, can lead to negative health effects in humans and livestock. Research reported here shows that new types of genetically-engineered Bt maize hybrids (Cry1Ab x Vip3Aa) reduce injury from European corn borer, corn earworm, and western bean cutworm and are more likely to yield high quality, low-fumonisin grain compared to hybrids lacking insect resistance. European corn borer males locate female moths by zeroing in on mating pheromones produced by females. Scientists learned several years ago that there are two different types of corn borers (races), those that produce Z or E pheromones, which differ in some important aspects of their ecology and behavior. The Z race is the most common type and occurs throughout corn growing regions of the U.S. east of the Rockies, whereas the E race occurs only in the eastern U.S. Until research reported here, these types of corn borers could not be easily identified because they look identical. Now a molecular assay that focuses on the genes controlling pheromone type easily distinguishes the E and Z races. Studies with the new assay revealed that hybridization between races is much more common than previously suspected. The surprisingly high frequency at which these two types of corn borers hybridize suggests that if Bt resistance develops in E-race populations in the Eastern United States, it will spread quickly to the Z race and then spread into the Corn Belt. Estimates of gene flow between pheromone races are important to university, government, and industry scientists seeking to assess the potential for the spread of Bt resistance traits in European corn borer populations. Another study describes a novel genetic mechanism that allows larvae of some European corn borers to survive Bt maize. This information will be used by researchers in the public and private sectors as well as in regulatory agencies to obtain a greater understanding of Bt resistance mechanisms in insect populations and evaluate insect resistance management practices. Additionally, studies in collaboration with researchers from the Universities of Nebraska and the University of Delaware were conducted for a second field season to investigate larval movement for fall armyworm among Bt and non-Bt corn hybrids. Collaborative research with Chinese scientists suggests that moths surviving a Bt crop may be more prone to migrate, which could increase the area receiving damaging infestations of immigrants. This information will be used by university and government scientists in the U.S., China, and throughout the world to better understand the mechanisms controlling migration and reproduction in many related migratory insect pests, as well as the possible role of Bt crops in changing patterns of infestation in some species. Additionally, a research project in collaboration with a researcher from the University of Nebraska funded by USDA Biotechnology Risk Assessments Grants (BRAG) was completed, which investigated fitness costs associated with Cry1F resistance in European corn borer. The study focused on Bt crops that are widely planted and enable management of key insect pests while reducing the use of conventional insecticides. However, the evolution of Bt resistance could diminish these benefits. Fitness costs of Bt resistance occur in the absence of Bt toxin when individuals with resistance alleles show a reduction in fitness relative to susceptible individuals, and can delay the evolution of resistance. Ecological factors including host plant variety can affect the magnitude of fitness costs, and consequently, the degree to which fitness costs delay resistance. Fitness costs associated with insect resistance are important to understand because, if they occur, they can delay the evolution of resistance. In a study of Cry1F-resistant European corn borer, however, no fitness costs were detected. This information is valuable to maize growers and scientists interested in delaying insect resistance to Bt maize, because it allows for a more accurate estimation of the potential for European corn borer to evolve resistance to Cry1F maize. A study produced as part of this project in collaboration with entomologists in China demonstrates that apparent activation of the beet webworm immune system in response to crowding may contribute to population outbreaks characteristic of this pest. Other crop pests probably use the same strategy. This information will be used by university and government scientists in the U.S., China, and throughout the world to better understand the mechanisms controlling explosive growth of outbreak insect populations, and thus lead to better methods for their prediction and management.

Publications

  • Type: Journal Articles Status: Published Year Published: 2013 Citation: Bowers, E. Hellmich, R.L., Munkvold, G.P. 2013. Vip3Aa and Cry1Ab proteins in maize reduce Fusarium ear rot and fumonisins by deterring kernel injury from multiple Lepidopteran pests. World Mycotoxin Journal 6:2, 127-135.
  • Type: Journal Articles Status: Published Year Published: 2013 Citation: Cheng, Y., Luo, L., Jiang, X., Sappington, T.W. 2012. Synchronized oviposition triggered by migratory flight intensifies larval outbreaks of beet webworm. PLoS One. 7(2):e31562.
  • Type: Journal Articles Status: Published Year Published: 2013 Citation: Coates BS, Johnson H, Kim KS, Hellmich RL, Abel CA, Mason C, Sappington TW 2013. Frequency of hybridization between Ostrinia nubilalis E-and Z-pheromone races in sympatric geographic regions of the United States. Ecology and Evolution doi: 10.1002/ece3.639
  • Type: Journal Articles Status: Published Year Published: 2012 Citation: Hellmich, R. L. & Hellmich, K. A. (2012) Use and Impact of Bt Maize. Nature Education Knowledge 3(10):4.
  • Type: Journal Articles Status: Published Year Published: 2013 Citation: Jiang, X.F., Chen, J., Zhang, L., Sappington, T.W., Luo, L.Z. 2013. Increased long flight activity triggered in beet armyworm by larval feeding on diet containing Cry1Ac protoxin. PLOS ONE 8(5): e63554.
  • Type: Journal Articles Status: Published Year Published: 2013 Citation: Kong, H., Luo, L., Sappington, T.W., Jiang, X., Zhang, L., Cheng, Y. 2013. Density-dependent prophylaxis in crowded beet webworm, Loxostege sticticalis (Lepidoptera: Pyralidae) larvae to a parasitoid and a fungal pathogen. International Journal of Pest Management DOI:10.1080/09670874.2013.807957
  • Type: Journal Articles Status: Published Year Published: 2013 Citation: Bruner, R. F., E. W. Hodgson, and A. J. Gassmann. Effects of Rag1 on the Preference and Performance of Soybean Defoliators. Journal of Economic Entomology 106.6 (2013): 2577-2584.
  • Type: Journal Articles Status: Published Year Published: 2013 Citation: Wang, L., Jiang, X., Luo, L., Stanley, D., Sappington, T. W. and Zhang, L. (2013), A cadherin-like protein influences Bacillus thuringiensis?Cry1Ab toxicity in the oriental armyworm, Mythimna separata. Environmental Microbiology Reports, 5: 438443. doi: 10.1111/1758-2229.12036.
  • Type: Journal Articles Status: Published Year Published: 2013 Citation: Agunbiade, T. A., et al. Development of Reference Transcriptomes for the Major Field Insect Pests of Cowpea: A Toolbox for Insect Pest Management Approaches in West Africa. PloS one 8.11 (2013): e79929.
  • Type: Book Chapters Status: Published Year Published: 2013 Citation: Kim, K. S., and T. W. Sappington. 2013. Microsatellite data analysis for population genetics. Pp. 271-295. In: S. K. Kantartzi (ed.), Microsatellites: Methods and Protocols. Methods in Molecular Biology, Humana Press, Springer Science+Business Media, LLC, New York.
  • Type: Journal Articles Status: Published Year Published: 2013 Citation: Dyer, J.M., Sappington, T.W., Coates, B.S. Evaluation of tolerance to Bacillus thuringiensis toxins among western bean cutworm (Lepidoptera; Noctuidae). Journal of Economic Entomology 106.6 (2013): 2467-2472.
  • Type: Journal Articles Status: Published Year Published: 2013 Citation: Coates, B.S., Sumerford, D.V., Hellmich, R.L., Abel, C.A. Unlinked genetic loci control the reduced transcription of aminopeptidase N 1 and 3 in the European corn borer and determine tolerance to Bacillus thuringiensis Cry1Ab toxin. Insect Biochemistry Molecular Biology 43.12 (2013): 1152-1160.


Progress 01/01/12 to 12/31/12

Outputs
OUTPUTS: Behavioral, ecological and genetic studies were conducted on insect pests of corn: European corn borer (ECB, Ostrinia nubilalis), and western bean cutworm (WBCW, Striacosta albicosta), and fall armyworm, (FAW, Spodoptera frugiperda). A new type of DNA marker called SIRRL (Sequencing Individuals in Reduced Representation Libraries) based on Illumina sequencing was developed using families of ECB. The test run was successful, demonstrating that the method for library preparation and paired-end sequencing worked as well as conceived. Data quality was excellent, as was the quantity of paired reads: 89 million from a single lane. A strategy for discovery and development of single nucleotide polymorphism (SNP) markers through Illumina sequencing of the adult transcriptome of WBCW was demonstrated, yielding 68 new markers suitable for population genetics work. New SNP markers were developed that differentiate the Z and E pheromone races of ECB, and these were validated in collaboration with the University of Delaware in an experiment that paired SNP-based genotypes with gas chromatograph estimates of female pheromone components. Results showed that SNP markers correctly identified greater than 97.5% of E and Z individuals. These SNP markers were used to genotype ECB from multiple locations in Pennsylvania and New York, where topography may reduce gene flow. Preliminary analyses using 60 other SNP markers indicate that gene flow in the E race is less than within the Z race, and that topography may isolate populations under certain conditions. Larval movement for European corn borer and fall armyworm between Bt and non-Bt corn was studied in collaboration with researchers from Universities of Nebraska and Delaware. Fitness costs associated with Cry1F resistance in ECB were studied in collaboration with University of Nebraska. Survival, weight and developmental rate were measured for Cry1F-resistant and Cry1F-susceptible larvae on vegetative and reproductive stages of three different corn lines, one of which possessed moderate DIMBOA-based resistance to ECB. One scientist in the project co-organized a workshop entitled "Surrogate Species Selection for Assessing Potential Adverse Environmental Impacts of Genetically Engineered Plants on Non-Target Organisms" with scientists from Center for Environmental Risk Assessment (CERA), US Environmental Protection Agency, Switzerland, Argentina, Pioneer Hi-Bred and Dow AgroSciences. The objectives were to identifying key criteria for surrogate species selection for early-tier, semi-field, and field testing; and identify best practices for surrogate testing, with a focus on facilitating data transportability among regulators of genetically-engineered crops. A practical guide for analyzing microsatellite data has been accepted for publication. It focuses on statistical analyses and relevant population genetic software programs commonly employed in the field of population genetics and molecular ecology. Methods and results were disseminated through publication of peer-reviewed papers, abstracts, on-line reports, presentations at scientific meetings, and presentations to individual stakeholder groups. PARTICIPANTS: Aaron Gassmann, Principal Investigator; Richard Hellmich, Principal Investigator; Tom Sappington, Principal Investigator; Brad Coates, Principal Investigator; Craig Abel, Principal Investigator; Jennifer Petzold-Maxwell, Postdoctoral Associate, Michael Rausch Graduate Research Assistant TARGET AUDIENCES: This research targets scientists and regulators interested in managing insect resistance to Bt corn, improving non-target evaluations of GM crops or both. Also this research targets corn growers interested in integrated management approaches to control insect pests of corn. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.

Impacts
The strategy for SNP marker development based on Illumina sequencing of the adult transcriptome not only provides significant genetic resources for future research on western bean cutworm, but demonstrates the power and economy of applying second-generation sequencing to previously under-studied species. This information will be used by university, government, and industry scientists who study western bean cutworm, and all researchers around the globe who face the same problem of needing to develop markers for a little-studied species at reasonable cost, regardless of whether it is an insect or another kind of organism. The practical guide to microsatellite analyses will make it possible for both students and experienced scientists to analyze and apply their genotype data immediately to questions related to gene flow and population genetic structure. It provides links to freeware and details of pitfalls and other considerations in working with such data, that usually one must learn by trial-and-error. For many years scientists studying ECB have needed an easy way to identify Z and E pheromone races because previous methods were tedious, required newly-merged adults and could only use females. This new DNA method is more efficient and allows scientist to determine the pheromone race of any insect stage and either sex. It has already been used by a graduate student in this project to verify and correct identification errors in a population genetics study of ECB in the eastern U.S.

Publications

  • Tolulupe AA, Coates BS, Kim KS, Forgacs D, Margam VM, Murdock LL, Ba M, Binso-Dabire CL, Baoua I, Ishiyaku MF, Manuele T, Pittendrich BR. 2012. The spatial genetic differentiation of the legume pod borer, Maruca vitrata F. (Lepidoptera: Pyralidae) populations in West Africa. Bulletin of Entomological Research 17:1-11.
  • Xie, D., L. Luo, T. W. Sappington, X. Jiang, and L. Zhang. 2012. Comparison of reproductive and flight capacity of Loxostege sticticalis (Lepidoptera: Pyralidae), developing from diapause and non-diapause larvae. Environmental Entomology 41: 1199-1207.
  • Kang J, Onstad DW, Hellmich RL, Moser SE, Hutchison WD, Prasifka JR. Modeling the impact of cross-pollination and low toxin expression in corn kernels on adaptation of European corn borer (Lepidoptera: Crambidae) to transgenic insecticidal corn. Environmental Entomology 41(1): 200-211.
  • Kim KS, Coates BS, Hellmich RL, Sappington TW. 2011. Genetic structure and gene flow among European corn borer populations from the Great Plains to New York. Agricultural and Forest Entomology 13:383-393.
  • Miller, N. J., J. Sun, and T. W. Sappington. 2012. High-throughput transcriptome sequencing for SNP and gene discovery in a moth. Environmental Entomology 41: 997-1007.
  • Cheng, Y. X., L. Z. Luo, X. F. Jiang, and T. W. Sappington. 2012. Synchronized oviposition triggered by migratory flight intensifies larval outbreaks of beet webworm. PLoS ONE 7(2): e31562.
  • Coates BS, Hellmich RL, Grant DM, Abel CA. 2012. Mobilizing the genome of Lepidoptera through novel sequence gains and end creation by non-autonomous Lep1 Helitrons. DNA Research 19(1):11-21.
  • Hellmich RL, Hellmich KA. 2012. Use and impact of Bt maize. Nature Education Knowledge 3(5):4.
  • Huesing J, Romeis J, Ellstrand N, Raybould A, Hellmich RL, Wolt J (others). 2012 .Regulatory considerations surrounding the deployment of Bt-expressing cowpea in Africa: Report of the deliberations of an expert panel. GM Crops 2(3): 211-224.
  • Jiang X, Zhai H, Wang L, Luo L, Sappington TW, Zhang L. 2012. Cloning of the heat shock protein 90 and 70 genes from the beet armyworm, Spodoptera exigua, and expression characteristics in relation to thermal stress and development. Cell Stress and Chaperones 17:67-80.
  • Siegfried, BD, Hellmich, RL. 2012. Understanding successful resistance management: The European corn borer and Bt corn in the United States. GM Crops 3(3): http://dx.doi.org/10.4161/gmcr.20715
  • Tian JC, Collins HL, Romeis J, Naranjo SE, Hellmich RL, Shelton AM. 2012. Using field-evolved resistance to Cry1F maize in a lepidopteran pest to demonstrate no adverse effects of Cry1F on one of its major predators. Transgenic Research DOI 10.1007/s11248-012-9604-4.


Progress 01/01/11 to 12/31/11

Outputs
OUTPUTS: In the past year behavior, ecological and genetic studies were conducted on the corn insect pests, European corn borer (ECB, Ostrinia nubilalis), and western bean cutworm (WBCW, Striacosta albicosta). Collaboration with scientists from China was continued with the goal to understand principles underlying long-distance migration of agricultural crop pests, especially moth species in the family Noctuidae, which includes a number of pest species worldwide. Research in collaboration with scientists from University Illinois and University Nebraska focused on the ECB larval movement among Bt and non-Bt corn plants and produced a model to evaluate seed mixtures as an insect resistance management (IRM) strategy. Two co-PIs of the project were invited by Environmental Protection Agency Office of Pesticide Programs in Washington D.C. to discuss IRM modeling project and provide recommendations based on this project. Related to this, a scientist was invited to participate on EPA science advisory panel "Scientific issues Associated with Insect Resistance Management for SmartStax Refuge-in-the-Bag, a Plant-Incorporated Protectant (PIP) Corn Seed Blend". Collaboration with scientists from Switzerland, Cornell University, ARS in Arizona and International Life Sciences Institute provided recommendations for experimental designs for early-tier laboratory studies used in risk assessments to evaluate potential adverse impacts of arthropod-resistant genetically engineered (GE) plants on non-target arthropods. In collaboration with scientists from South Korea and Penn State University genetic markers were used to examine differentiation between ECB populations in Pennsylvania within each of two races and separated by possible topographical barriers to movement. Research with a scientist from University of Nebraska is deciphering the genetic basis of resistance of two colonies of ECB that are resistant to Bt toxins. A study with a Master's student has produced selected lines of ECB showing plant abandonment by ECB larvae is a heritable trait. High throughput DNA sequencing technology was used to develop 22 genetic markers for the WBCW and ~800 genetic markers for ECB. ECB colonies resistant to Bt corn obtained from University Nebraska were established in Ames for tests to determine whether Bt resistance has fitness costs. One scientist co-organized and co-directed, the effort to create a large multidisciplinary research team to develop Agricultural Crops as Ecosystems (ACE) Center on ISU campus, and another served on the core organizing committee. One scientist provided technical and strategic advice to several institutions on blanket agreements with Dow, Pioneer, Syngenta and Bayer for conducting research on commercial GE seeds. Related to the blanket agreements, a symposium entitled "Reaching Out Across the Bag-tag" was co-organized for the annual Entomological Society of America meeting. Methods and results were disseminated through publication of peer-reviewed papers, abstracts and on-line industry reports, and presentations at scientific meetings and to individual stakeholders. PARTICIPANTS: Nothing significant to report during this reporting period. TARGET AUDIENCES: This research targets scientists and regulators interested in managing insect resistance to Bt corn, improving non-target evaluations of GM crops or both. Also this research targets corn growers interested in integrated management approaches to control insect pests of corn. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.

Impacts
Planting genetically engineered Bt corn suppresses areawide populations of European corn borers. A team of scientists, including researchers in Ames, Iowa, showed areawide pest suppression provides significant economic benefits to farmers that use Bt corn and even to neighboring farmers who grow non-transgenic varieties of corn. The researchers estimate that between 1996-2009 farmers in Iowa, Illinois, Minnesota, Nebraska and Wisconsin received cumulative economic benefits of nearly $7 billion, with benefits of more than $4 billion for non-Bt corn farmers alone. Good estimates of insect migration rate are very difficult to obtain. Researchers from Ames, Iowa used DNA markers and independent estimates of population density to calculate migration rate of corn borer adults. The results indicated that 15% of these moths disperse > 12 km/gen. This provides the first quantitative estimate of typical dispersal distances in this pest, and will be useful to officials in regulatory agencies responsible for resistance management regulations for Bt crops. It also will be useful to university, government, and industry scientists and modelers trying to understand and predict rates of resistance development in European corn borer to Bt corn. For many years scientists could not understand why microsatellite DNA was not a very useful marker for lepidopteran genetic studies, such markers have been very useful tools for other insects. Research discovered a mobile section of DNA that is able to autonomously move among different positions within the genome of Lepidoptera. These mobile DNAs are a common feature within the genomes of Lepidoptera, and appear to carry microsatellite DNA. The consequence of microsatellite movement within these genomes is that they are no longer useful as a genetic marker. This discovery also has major implications for the study of lepidopteran crop pests and lends insight into how their genomes have evolved. Interplant movement of ECB neonates (young larvae) was less of a concern than movement of older larvae due to the tendency of many neonates to disperse from corn before feeding. Older larvae, however, at least at high densities, readily move from non-Bt to Bt corn plants. Modeling suggests that stakeholders examine toxin-survival rates for older larvae and to take into account that larvae may feed on different parts of Bt corn as they develop. Impact of this project could influence insect resistance management policies not only in the United States but also other countries interested in managing resistance of lepidopteran pests to Bt corn.

Publications

  • Coates BS, Sumerford DV, Hellmich RL, Abel CA, Siegfried BD. 2011. A single major QTL controls expression of larval Cry1F resistance trait in Ostrinia nubilalis (Lepidoptera: Crambidae). Genetica 139(8):961-972.
  • Coates BS, Bayles DO, Wanner KW, Fraser LM, Hellmich RL, Abel CA, Robertson HM, Sappington TW. 2011. The application and performance of single nucleotide polymorphism (SNP) markers for population genetic analyses of Lepidoptera. Frontier Genet 2:38.
  • Coates BS, Kroemer, JA, Sumerford DV, Hellmich RL. 2011. A novel class of miniature inverted repeat transposable elements (MITEs) that contain hitchhiking (GTCY)n microsatellites. Insect Mol Biol 20(1):15-27.
  • Coates BS, Sumerford DV, Hellmich RL, Lewis LC. 2010. A Helitron-like transposon superfamily from Lepidoptera disrupts (GAAA)n microsatellites and is responsible for flanking sequence similarity within a microsatellite family. J Mol Evol 70:278-288.
  • Jiang, X. F., Luo, L. Z., Zhang, L., Sappington, T. W., Hu, Y. 2011. Regulation of migration in the oriental armyworm, Mythimna separata (Walker) in China: A review integrating environmental, physiological, hormonal, genetic, and molecular factors. Environmental Entomology 40(3):516-533.
  • Jiang, X.F., Luo, L.Z., Sappington, T.W. 2010. Relationship of flight and reproduction in beet armyworm, Spodoptera exigua (Lepidoptera: Noctuidae), a migrant lacking the oogenesis-flight syndrome. Journal of Insect Physiology 56(11):1631-1637.
  • Hutchison, W. D., E. C. Burkness, P. D. Mitchell, R. D. Moon, T. W. Leslie, S. J. Fleischer, M. Abrahamson, K. L. Hamilton, K. L. Steffey, M. E. Gray, R. L. Hellmich, L. V. Kaster, T. E. Hunt, R. J. Wright, K. Pecinovsky, T. L. Rabaey, B. R. Flood, E. S. Raun. 2010. Areawide suppression of European corn borer with Bt maize reaps savings to non-Bt maize growers. Science 330:222-225.
  • Onstad DW, Mitchell PD, Hurley TM, Lundgren JG, Porter RP, Krupke CH, Spencer JL, DiFonzo CD, Baute TS, Hellmich RL, Buschman LL, Hutchison WD, Tooker JF. 2011. Seeds of change: corn seed mixtures for resistance management and integrated pest management. J. Econ Entomol. Apr;104(2):343-52.
  • Kim, K.S., Jones, G.D., Westbrook, J.K., Sappington, T.W. 2010. Multidisciplinary fingerprints: Forensic reconstruction of an insect reinvasion. Journal of the Royal Society Interface 7(45):677-686.
  • Kroemer JA, Coates BS, Nusawardani T, Rider SD, Fraser JM, Hellmich RL. 2011. A rearrangement of the Z chromosome topology influences the sex-linked gene display in the European corn borer, Ostrinia nubilalis. Mol Genet Genomics 286(1):37-56.
  • Prasifka, J. R., Buhay, J. E., Sappington, T. W., Heaton, E. A., Bradshaw, J. D., Gray, M. E. 2011. Stem-boring caterpillars of switchgrass in the Midwestern United States. Annals of the Entomological Society of America 104(3):507-514.
  • Romeis, J., R. L. Hellmich, M. P. Candolfi, K. Carstens, A. De Schrijver, A. M. R. Gatehouse, R. A. Herman, J. E. Huesing, M. A. McLean, A. Raybould, A. M. Shelton, A. Waggoner. 2011. Recommendations for the design of laboratory studies on non-target arthropods for risk assessment of genetically engineered plants. Transgenic Res. 20:1-22.


Progress 01/01/10 to 12/31/10

Outputs
OUTPUTS: In the past year ecological and genetic studies were conducted on the corn insect pests, European corn borer (ECB, Ostrinia nubilalis), western bean cutworm (WBCW, Striacosta albicosta), and western corn rootworm (WCR, Diabrotica virgifera virgifera). Genetic markers were used to examine differentiation between two populations of ECB within each of two races separated by possible barriers to movement in Pennsylvania. Results indicate that gene flow is high between sites, over time, and between and within races, suggesting that resistance to transgenic corn may be slow to develop even in populations partially isolated in mountain valleys. A molecular genetics approach was taken to isolate two genes (slowmo and shaker) from ECB that are known behavior-linked genes from the fruit fly (Drosophila melanogaster). The intention is to learn if these genes are associated with ECB movement, particular larval movement. The manner in which Lepidoptera larvae move in the field can have widespread impacts on the methods used to manage them, and on the sustainability of these methods. A laboratory colony of ECB was selected for increased Cry1F tolerance, which shows >12,000-fold compared to susceptible. Genome linkage maps show that Cry1F resistance trait is controlled by a single quantitative trait locus (QTL) on linkage group 12. Laboratory flight mill experiments showed that infection of ECB with Nosema pyrausta has a negative effect on moth flight performance. Analyses indicate that the negative effects are due to competition by the pathogen for adult energy reserves. A map of the Z sex chromosome for European corn borer was developed that incorporates and compares a genetic map, gene expression data, and sequence data gathered for a panel of 50 sex-linked genes identified in the silkworm genome. Genes located on the Z chromosome in Lepidoptera (butterflies and moths) play important roles in establishing the numbers of insects produced per season (voltinism) as well as the ability of opposite sexes to locate mates in the field (male pheromone responses). High throughput DNA sequencing technology was used to develop 22 genetic markers for the WBCW, a growing pest of corn in the Midwest, which will allow detailed studies of movement and gene flow. Gene sequences from a pathogen, probably a species of Nosema, were also found in the DNA isolated from the WBCW moths, which will allow development of a DNA test to determine the presence of this pathogen and level of infection in individual moths. Over 1,500 possible new genetic markers were identified from WCR and submitted for sequencing and verification. WCR samples were collected from 10 locations in its original range in Colorado and western Kansas, including the species type-location (Wallace County, Kansas), for genetic diversity and gene flow analyses. Samples from this area are important for obtaining estimates of long-range movement, and the DNA has been isolated in preparation for determining genetic differences between locations which will allow such estimates to be made. PARTICIPANTS: Richard Hellmich, Tom Sappington, Aaron Gassmann, Brad Coates, Craig Abel TARGET AUDIENCES: Results will be used by university and government scientists trying to understand and model European corn borer population dynamics, as well as potential development and spread of resistance to transgenic Bt-corn in the presence of natural Nosema infections. Research findings will be used by regulatory agencies, biotech seed industry scientists, and other government and university scientists in the US, Europe, and Asia who conduct research on insect resistance management, and who are involved in developing, recommending, or implementing improved refuge requirements for Bt corn. This information will be incorporated into a model and used to guide recommendations for new types of refuges for managing ECB resistance to Bt corn. Methods, results, and management recommendations were disseminated through publication of peer-reviewed papers and presentations at scientific meetings and to individual stakeholders. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.

Impacts
Researchers demonstrated the importance of long-distance movement of ECB to its population dynamics and to the effectiveness of current insect resistance management strategies being used to slow development of resistance to transgenic Bt-corn. In flight mill experiments, Nosema infection has a negative effect on measures of flight distance, duration, and speed, especially in males, with effects in females detected only when infection was at a moderate level. The relationship between Nosema infection, wing length, body weight, and flight performance indicates that the negative effects infection on flight activity are due to reduction in fuel reserves needed to support flight. Because ECB can feed on other kinds of plants besides corn, it has been suggested that moths emerging from this "unstructured" refuge might be enough that the percentage of required non-Bt corn "structured" refuge could be reduced. By using a technique that measures the form of carbon in the larval diet typical of corn or non-corn plants the larvae fed on, researchers in collaboration with Cornell University found that one race of ECB (called "E race") where females produce a particular form of male-attractant pheromone ("E pheromone") does produce a relatively substantial proportion of adults from non-corn host plants; however, the other kind of ECB, the Z race, is produced almost entirely on corn. Even though unstructured refuge might be possible for the E race, it is not possible for the Z race, and because we found that in every county where the E race occurs the Z race also occurs, our study does not support a relaxation of the current refuge requirements for ECB. Genes located on the Z sex chromosome in lepidoptera play important roles in establishing the numbers of insects produced per season as well as the ability of opposite sexes to locate mates. This study provides an enhanced resolution of the Z chromosome architecture in the ECB, incorporating and comparing a genetic map, gene expression data, and sequence data gathered for a panel of 50 sex-linked genes identified in the silkworm genome. We have discovered a mobile section of DNA that is able to autonomously move among different positions within the genome of a lepidopteran insect. These mobile DNAs are a common feature within the genomes of Lepidoptera, and appear to carry microsatellite DNA. The consequence of microsatellite movement within these genomes is that they are no longer useful as a genetic marker, and this discovery has a major implication on the study of lepidopteran crop pests. When ECB larvae from a colony selected for Cry1Ab resistance were exposed to diet with Cry1Ab toxin, they did not show a greater ability to avoid toxins compared with susceptible ECB. This information will be incorporated into a model and used to guide recommendations for new types of refuges for managing ECB resistance to Bt corn. One possibility is the use of blended seed refuges, which would be easier for growers to implement than current insect resistance management practices.

Publications

  • O'Rourke, M.E., Sappington, T.W., Fleischer, S.J. 2010. Managing resistance to Bt crops in a genetically variable insect herbivore, Ostrinia nubilalis. Ecological Applications 20(5):1228-1236.
  • Dorhout, D.L., Sappington, T.W., Lewis, L.C., Rice, M.E. 2010. Flight behaviour of European corn borer infected with Nosema pyrausta. Journal of Applied Entomology (Early View online, doi: 10.1111/j.1439-0418.2010.01523.x)
  • Kim, K.S., Bagley, M.J., Coates, B.S., Hellmich II, R.L., Sappington, T.W. 2009. Spatial and temporal genetic analyses show high gene flow among European corn borer (Lepidoptera: Crambidae) populations across the central U.S. Corn Belt. Environ. Entomol. 38(4):1312-1323.
  • Sappington, T.W., Ostlie, K.R., DiFonzo, C., Hibbard, B.E., Krupke, C.H., Porter, P., Pueppke, S., Shields, E.J., Tollefson, J.J. 2010. Conducting public-sector research on commercialized transgenic seed: In search of a paradigm that works. GM Crops 1(2):55-58.
  • Miller, N.J., Richards, S., Sappington, T.W. 2010. The prospects for sequencing the western corn rootworm genome. Journal of Applied Entomology 134(5):420-428.
  • Greenberg, S.M., Adamczyk Jr, J.J., Sappington, T.W., Jones, W.A., Liu, T. 2008. Interrelationship between plants and insects as the basis for IPM systems. Egyptian Journal of Agricultural Research. 86(1):133-148.
  • Greenberg, S.M., Sappington, T.W., Adamczyk Jr, J.J., Liu, T., Setamou, M. 2008. Effects of photoperiod on boll weevil (Coleoptera: Curculionidae) development, survival, and reproduction. Environmental Entomology. 37(6):1396-1402.
  • Spurgeon, D.W., Sappington, T.W., Rummel, D.R. 2008. Host-free survival of boll weevils (Coleoptera: Curculionidae) from two regions of Texas. Southwest Entomologist 33:151-152.


Progress 01/01/09 to 12/31/09

Outputs
OUTPUTS: Activities: Research has focused on the ecology and genetics of lepidopteran pests of corn. Difficulty associated with the use of microsatellite DNA markers for moths was attributed to transposons that made the microsatellites very repetitive. Research has continued on deciphering Bt corn resistance in European corn borer; and resistance monitoring has established corn borer resistance to Bt certain types of corn is more common than anticipated. Also, population genetic studies suggest that the range expansion of western bean cutworm is probably attributed to sudden change in the agricultural environment rather than this pest surmounting of a physical barrier to movement. This information was communicated to the public through journal articles and professional meetings. Events: Invited to participate in VI Brazilian Biosafety Congress and 1st Latin American Symposium on Biotech Products and to present paper entitled "Challenges for managing insect resistance for the next generation of Bacillus thuringiensis (Bt) maize hybrids" and to participate on Expert's Panel "Biosafety of Bt maize - more than 15 years of published experience" Rio de Janeiro, Brazil. Invited to participate in IWGO conference and present talks "Possible new approaches to manage insect resistance for the next generation of Bt maize", "ECB dispersal at small and large scales: New insights, maddening mysteries, and the elusive unified theory of everything," Munich, Germany. Invited to participate on a Cowpea Expert Panel by members of the African Agricultural Technology Foundation (AATF) and the Danforth Foundation to evaluate the possibility of introducing Bt cowpea into Africa, St. Louis, MO. Co-organized a symposium "Regulation of Transgenic Crops: The State of the Science" for the Annual Meeting of the Entomological Society of America (ESA), Indianapolis, IN. Services: Served on EPA FIFRA Science Advisory Panel (SAP) "A Set of Scientific Issues Being Considered by the Environmental Protection Agency Regarding: The Data Required to Register Plant-Incorporated Protectants". Washington, D. C., February 2009. Also served on EPA SAP "Evaluation of the Resistance Risks from Using a Seed Mix Refuge with Pioneer's Optimum AcreMax1 Corn Rootworm-Protected Corn" Washington, DC, February 2009. Served as Plant-Insect Ecosystems Section (ESA) rep and Chair of Publications Council and rep to Journal of Medical Entomology Editorial Board. Served as Subject Editor for Environmental Entomology, Interim Principal Editor for Crop Protection, and on the Scientific Advisory Board for Journal of Applied Entomology. Dissemination: Provided slide show to members of the African Agricultural Technology Foundation about the basic principles of managing insect resistance to transgenic crops. Three students had internships: two Iowa State University students and one Ames High School student. Served as sabbatical host for senior entomologist from the Chinese Academy of Agricultural Science specializing in migration of insect pests of agriculture. PARTICIPANTS: Craig A. Abel, USDA-ARS Research Entomologist and Research Leader at the USDA-ARS, Corn Insect and Crop Genetics Research Unit (CICGRU). Richard L. Hellmich, Assistant Professor, USDA Collaborator, USDA Research Entomologist, CICGRU. Thomas W. Sappington, Assistant Professor, USDA Collaborator, USDA Research Entomologist, CICGRU. Douglas V. Sumerford, Assistant Professor, USDA Collaborator, USDA Research Entomologist, CICGRU. Brad S. Coates, USDA Research Geneticists (post-doc), CICGRU. Nicholas J. Miller, USDA Research Entomologist (post-doc), CICGRU. Susan E. Moser, USDA Research Entomologist (post-doc), CICGRU. Jeremy A. Kroemer, USDA Research Entomologist (post-doc), CICGRU. TARGET AUDIENCES: Customers include agricultural scientists, especially entomologists and corn geneticists, associations of corn producers, producers from big and small farms, crop consultants, organic food producers, gene suppliers (currently Monsanto, Pioneer, Dow AgroSciences, and Syngenta), the U.S. Environmental Protection Agency, the biotechnology division of USDA Animal Plant Health Inspection Service, state agricultural extension specialists, consumers, and students in the agricultural sciences. New customers may include the USDA Natural Resources Conservation Service and sustainable agriculture organizations such as the Leopold Center, Ames IA. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.

Impacts
The research has impacted technical and regulatory programs and has helped establish an international reputation in insect resistance management, evaluation of possible non-target effects of genetically modified crops, and insect genetics and ecology. Outcome: Microsatellites in the European corn borer were found to be highly repetitive and often associated with mobile elements or transposons. Impact: Many scientists have tried to use microsatellite DNA for population and genetic studies in moths and butterflies. This research will point them toward other types of DNA markers (e.g., SNPs) that are much easier to use. Ultimately, more accurate estimates of lepidopteran population structure will be useful for all scientists and regulators interested in lepidopteran genetics. Outcome: Aminopeptidase N (apn) genes are candidate Bt resistance genes, and one of these genes, the apn1 gene, was shown not to express in European corn borers that have > 2500-fold resistance to Cry1Ab. Partial genome assembly in the European corn borer indicates 7 apn genes are encoded near each other. Impact: The tandem arrangement of apn genes in European corn borer suggests these genes evolved as a single genetic unit, and cross-resistance based upon different apn genes may be unlikely because of their close linkage. This information is useful to all stakeholders interested in producing pyramided Bt crops for the purposes of controlling lepidopteran pests. Outcome: As part of a funded USDA Biotech Risk Assessment Grant (BRAG) in collaboration with the Univ. of Nebraska, designed the experiment that isolated two families of European corn borer exhibiting resistance to Cry1F. Analyses indicate an allele frequency >10-3. Impact: Resistance evolution models predict that allele frequencies >10-3 may result in the loss of Bt corn efficacy. These results are important to regulators and scientists interested in delaying European corn borer resistance to Bt corn. The results also will be important in the consideration of sustaining corn hybrids containing multiple Bt proteins. Outcome: Patterns of genetic variation in populations of the western bean cutworm (Striacosta albicosta) from its original western range to newly established populations in Iowa indicates a sudden change in the agricultural environment is more likely to have triggered the ongoing eastward range expansion through the Corn Belt, than the surmounting of a physical barrier to movement. Impact: The results support the idea that initiation of the range expansion may be related to the widespread adoption of Bt corn targeting European corn borer, and will help researchers home in on the mechanism maintaining the continued invasion of the eastern U.S.

Publications

  • Coates BS, Kim KS, Miller NJ, Sumerford DV, Sappington TW, Siegfried BD, Lewis LC. 2009. Comparative performance of single nucleotide polymorphism (SNP) and microsatellite markers for the detection of population differentiation in Diabrotica virgifera virgifera (Coleoptera: Chrysomelidae). J. Heredity 100: 556-564.
  • Coates BS, Sumerford DV, Hellmich RL, Lewis LC. 2009. Repetitive genomic elements in a European corn borer, Ostrinia nubilalis, bacterial artificial chromosome library were indicated by bacterial artificial chromosome end sequencing and development of sequence tag site markers: implications for lepidopteran genomic research. Genome 52: 57-67.
  • Hellmich, R. L., R. Albajes, D. Bergvinson, J. R. Prasifka, Zhen-Ying Wang and M. J. Weiss. 2008. The present and future role of insect-resistant genetically modified maize in IPM. In Integration of Insect-Resistant Genetically Modified Crops within IPM Programs, edited by J. Romeis, A. M. Shelton and G. G. Kennedy. Springer, New York.
  • Kim KS, Bagley MJ, Coates BS, Hellmich RL, Sappington TW. 2009. Spatial and temporal genetic analyses reveal high gene flow among European corn borer populations across the central US corn belt. Environ Entomol 38: 1312-1323.
  • Kim, K. S., G. D. Jones, J. K. Westbrook, and T. W. Sappington. 2009. Multidisciplinary fingerprints: Forensic reconstruction of an insect reinvasion. J. R. Soc. Interface (published online before print October 14, 2009, doi:10.1098/rsif.2009.0345.)
  • Kim, K. S., Z. Szendrei, C. Rodriguez-Saona, P. G. Mulder, Jr., and T. W. Sappington. 2009. Molecular diagnostic for boll weevil (Coleoptera: Curculionidae) based on amplification of three species-specific microsatellites. J. Econ. Entomol. 102: 759-766.
  • Miller, N. J., D. L. Dorhout, M. E. Rice, and T. W. Sappington. 2009. Mitochondrial DNA variation and range expansion in the western bean cutworm (Lepidoptera: Noctuidae): no evidence for a recent population bottleneck. Environ. Entomol. 38: 274-280.
  • Prasifka, J. R., R. L. Hellmich and M. J. Weiss. 2009. Role of biotechnology in sustainable agriculture. In Integrated Pest Management, edited by E. B. Radcliffe, W. D. Hutchison and R. E. Cancelado. Cambridge University Press.
  • Romeis, J. M. Meissle, A. Raybould and R. L. Hellmich. 2009. Impact of insect-resistant transgenic crops on above-ground non-target arthropods. In Environmental Impact of Genetically Modified Crops, edited by N. Ferry and A. M. R. Gatehouse. CABI.


Progress 01/01/08 to 12/31/08

Outputs
OUTPUTS: Activities: In April a member of the Corn Insects and Crop Genetics Research Unit (CICGRU) was invited to visit and provide technical advice and guidance on insect migration to lead scientist, junior scientists, and graduate students of the Insect Migration research group at the Chinese Academy of Agricultural Science, Beijing, China. Also, a CICGRU member was invited in December to give a presentation to the Polish Farm Delegation to the United States entitled "Bacillus thuringiensis (Bt) Maize in the U.S.A." Events: Gave Keynote Address on western corn rootworm genetics research in the US at the DIABR ACT (The Western Corn Rootworm: Research and Long Term Management Needs for European Maize Production.), closing EU project meeting, Gottingen, Germany. Gave invited opening talk, "Molecular ecology of insect invasions: Why we care and why it is so challenging", to the National Research Initiative, Arthropods & Nematodes Biology & Management Programs Awardee Workshop, Reno, NV. Organized the Western Corn Rootworm Genome Sequencing Workshop, Entomological Society of America Annual Meeting, Reno, NV. Invited to give a presentation at the XXII Congresso Brasileiro De Entomologia entitled "Managing Insect Resistance to Bacillus thuringiensis (Bt) Maize in the USA: Current Strategies and Future Options," Uberlandia, Brazil. Invited to give two presentations at the XXIII International Congress of Entomology: "Developing IRM strategies for the next generation of insect-resistant maize" for Symposium entitled "Development, barriers and use of insect resistant transgenic crops in developing countries" and "The present and future role of insect-resistant genetically modified maize in IPM" for symposium entitled "Integration of insect-resistant GM crops within IPM programs," Durban, South Africa. Services: Served as Plant-Insect Ecosystems Section (ESA) rep to Publications Council and to Journal of Medical Entomology Editorial Board. Dissemination: Provided slide show with population genetics research on recent boll weevil reinvasion of a Texas eradication zone to J. Westbrook (APMRU) for 3 invited presentations to stakeholders including the National Cotton Council, Texas Boll Weevil Eradication Foundation Technical Advisory Committee, Boll Weevil Action Committee, and APHIS. Provided slide show on our newly developed molecular boll weevil diagnostic tool, for invited presentation to the TX Boll Weevil Eradication Fndtn. Tech. Advisory Comm. Provided information and demonstration of genetic marker development to three visiting scientists from the National Agricultural Products Quality Management Service of Korea. PARTICIPANTS: Leslie C. Lewis. Professor, USDA Collaborator, USDA-ARS Research Entomologist and Research Leader at the USDA-ARS, Corn Insect and Crop Genetics Research Unit (CICGRU) Richard L. Hellmich, Assistant Professor, USDA Collaborator, USDA Research Entomologist, CICGRU Thomas W. Sappington, Assistant Professor, USDA Collaborator, USDA Research Entomologist, CICGRU Douglas V. Sumerford, Assistant Professor, USDA Collaborator, USDA Research Entomologist, CICGRU Brad S. Coates, USDA Research Geneticists (post-doc), CICGRU Kyung Seok Kim, USDA Research Molecular Biologists (post-doc), CICGRU Nicholas J. Miller, USDA Research Entomologist (post-doc), CICGRU Jarrad R. Prasifka, USDA Research Entomologist (post-doc), CICGRU TARGET AUDIENCES: Customers include agricultural scientists, especially entomologists and corn geneticists, associations of corn producers, producers from big and small farms, crop consultants, organic food producers, gene suppliers (currently Monsanto, Pioneer, Dow AgroSciences, and Syngenta), the U.S. Environmental Protection Agency, the biotechnology division of USDA Animal Plant Health Inspection Service, state agricultural extension specialists, consumers, and students in the agricultural sciences. New customers may include the USDA Natural Resources Conservation Service and sustainable agriculture organizations such as the Leopold Center, Ames IA. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.

Impacts
The Corn Insects and Crop Genetics Research Unit has impacted technical and regulatory programs and has helped establish an international reputation in insect resistance management, evaluation of possible non-target effects of genetically modified crops, and insect genetics and ecology. Carbon isotope analysis revealed that alternative host plant use by E strain European corn borer, Ostrinia nubilalis, (ECB) is relatively high compared to Z strain, a study with important and far-reaching implications for insect resistance management for this insect in Bt corn. The demonstration that the Z strain ECB overlaps everywhere the E strain occurs, and the Z strain's low use of alternative hosts by the latter indicate that relaxing of structured refuge requirements on the basis of natural refuge is not justified and will help guide EPA policy decisions on petitions to modify refuge constraints. Demonstration that ECB bivoltine Z strain moths commonly disperse >100 km exposed the potential importance of E strain moths in the eastern U.S. in development of resistance to Bt corn. Findings in western corn rootworm genetics and ecology of the North American range expansion is affecting policy decisions as EU officials and scientists determine the best strategies to slow the range expansion in Europe. Population genetics studies on the western bean cutworm indicate that it's unexplained ongoing eastward range expansion through the Corn Belt was initiated by a sudden loss of an ecological exclusion mechanism rather than a fortuitous crossing of a barrier to movement. Genetic studies were conducted on lab-selected ECB that are resistant to Cry1Ab, an insecticidal protein produced by most Bt corn plants. An AFLP linkage map was developed including 253 markers on 31 autosomal chromosomes. These efforts may substantially accelerate efforts to prevent the development of ECB resistance to Bt corn plants by mapping chromosomal segments related to resistance. Nosema pyrausta a natural enemy of ECB, was found to significantly impact Cry1Ab-resistant ECB populations. Nosema has the potential to render individuals possessing resistance genes completely susceptible to corn tissue expressing Cry1Ab. Nosema therefore has the potential to retard resistance evolution to Cry1Ab. Populations of ECB often have high levels of N. pyrausta infections. Significant genetic variation was quantified in the laboratory for tolerance to infection by this microsporidium. Selection for increased tolerance by populations of the ECB will compromise Nosema's ability to control ECB.

Publications

  • Romeis, J., D. Bartsch, F. Bigler, M.P. Candolfi, M.M.C. Gielkens, S.E. Hartley, R.L. Hellmich, J.E. Huesing, P.C. Jepson, R. Layton, H. Quemada, A. Raybould, R.I. Rose, J. Schiemann, M.K. Sears, A.M. Shelton, J. Sweet, Z. Vaituzis and J.D. Wolt. 2008. Assessment of risk of insect-resistant transgenic crops to nontarget arthropods. Nature Biotech. 26:203-208.
  • Spurgeon, D. W., T. W. Sappington, and D. R. Rummel. 2008. Host-free survival of boll weevils (Coleoptera: Curculionidae) from two regions of Texas. Southwest. Entomol. 33:151-152.
  • Carroll, M. W., J. A. Glaser, R. L. Hellmich, T. E. Hunt, D. Calvin, T. W. Sappington, K. Copenhaver, and J. Fridgen. 2008. Detection of European corn borer infestation in Iowa corn plots using spectral vegetation indices derived from airborne hyperspectral imagery. J. Econ. Entomol. 101:1614-1623.
  • Coates B.S., Sumerford D.V., Lewis L.C. 2008. Segregation of Ostrinia nubilalis aminopeptidase 1 (APN1), cadherin, and bre5-like alleles from a Cry1Ab resistant colony are not associated with F2 larval weights when fed on toxin-containing diet. J. Insect Sci. 8:21.
  • Coates B.S., Sumerford D.V., Hellmich R.L., Lewis L.C. 2008. Mining an Ostrinia nubilalis midgut expressed sequence tag (EST) library for candidate genes and single nucleotide polymorphisms (SNPs). Insect Mol Biol 17(6):607-621.
  • Dorhout, D. L., T. W. Sappington, and M. E. Rice. 2008. Evidence for obligate migratory flight behavior in young European corn borer (Lepidoptera: Crambidae) females. Environ. Entomol. 37: 1280-1290.
  • Gray, M. E., T. W. Sappington, N. J. Miller, J. Moeser, and M. O. Bohn. 2009. Adaptation and invasiveness of western corn rootworm: Intensifying research on a worsening pest. Annu. Rev. Entomol. 54: 303-321.
  • Kim, K. S., C. T. Allen, and T. W. Sappington. 2008. Forum: Genetic profiling to determine potential origins of boll weevils (Coleoptera: Curculionidae) captured in a Texas eradication zone: Endemicity, immigration, or sabotage J. Econ. Entomol. 101:1729-1736.
  • Meihls, L. N., M. L. Higdon, B. D. Siegfried, N. J. Miller, T. W. Sappington, M. R. Ellersieck, T. A. Spencer, and B. E. Hibbard. 2008. Increased survival of western corn rootworm on transgenic corn within three generations of on-plant greenhouse selection. Proc. Natl. Acad. Sci. USA 105:19177-19182.
  • Meinke, L. J., T. W. Sappington, D.W. Onstad, T. Guillemaud, N. J. Miller, J. Komaromi, N. Levay, L. Furlan, J. Kiss, F. Toth. 2009. Western corn rootworm (Diabrotica virgifera virgifera LeConte) population dynamics. Agric. For. Entomol. 11:29-46.
  • Miller, N. J., T. Guillemaud, R. Giordano, B. D. Siegfried, M. E. Gray, L. J. Meinke, and T. W. Sappington. 2009. Genes, gene flow and adaptation of Diabrotica virgifera virgifera. Agric. For. Entomol. 11:47-60.
  • Prasifka, J.R., Lopez, M.D., Hellmich, R.L. 2008. Effects of insecticide exposure on movement and population size estimates of predatory ground beetles (Coleoptera: Carabidae). Pest Management Science. 64:30-36.
  • Prasifka, J.R., R.L. Hellmich, G.P. Dively, L.S. Higgins, P.M. Dixon and J.J. Duan. 2008. Selection of nontarget arthropod taxa for field research on transgenic insecticidal crops: Using empirical data and statistical power. Environ. Entomol. 37:1-10.


Progress 01/01/07 to 12/31/07

Outputs
OUTPUTS: Activities: Hosted (5 wks) and advised Borlaug Fellow from the Dept. of Applied Entomology, Agricultural Univ., Warsaw, Poland on a project related to evaluating non-target effects of Bt corn. Hosted (6 mo) and consulted with a Visiting Scholar from the Institute of Plant Protection, Chinese Academy of Agricultural Sciences in Beijing, China, on projects related to evaluating non-target effects of Bt corn and managing insect resistance to Bt corn. Hosted (2 wks) and trained a Visiting Scientist from the Dept of Crop Protection, National Institute of Agricultural Science and Technology, Seoul, South Korea on population genetics laboratory techniques and data analysis. Events: Participated in Workshop on Genetically Engineered Organisms, Wildlife, and Habitats, sponsored by the National Research Council, Irvine, CA. Invited to give three presentations in Poland: Distinguish Lecture Series, Warsaw Agricultural Univ., "Integrating GM Crops in IPM with Emphasis on Biological Control"; Institute of Plant Breeding and Acclimatization, Radzikow (Błonie) of the Ministry of Agriculture and Rural Development, "Environmental Risk Assessment and GM crop Registration Procedures in the U.S.A." and brief presentation at the Institute of Crop Sciences, Pulawy. Gave two invited talks at ESA symposia, San Diego, CA, "Genetic markers for corn rootworms: strategies, uses, and progress," and "Using molecular markers to characterize insect movement over large spatial scales." Gave an invited lecture to the ISU Osborn Research Club, "Ghost riders in the sky: Understanding insect dispersal by flight (and why we care)." Services: Served as subject editor for Environmental Entomology, ESA Section C representative to Editorial Board of J. Medical Entomology, and Section C representative to Entomological Society of America (ESA) Publications Council. Served on Science Advisory Board of J. of Applied Entomology. Consulted with seed industry representatives about novel ways to manage corn borer resistance to Bt corn. Products: After extensive screening and rigorous experimentation, several microsatellite markers were developed for European corn borers. Multiplexing protocols were developed for these markers combined with markers developed at Cornell Univ. and INRA in France at the request of French scientists. Developed a core set (universal panel) of microsatellite markers recommended for use in all future western corn rootworm population genetics studies. Use of these markers will allow direct comparisons between laboratories and studies, as well as direct sharing of genotype data when appropriate. Dissemination: Several scientists from USA and Europe are involved with efforts to develop laboratory tests to assess safety of GM plants for non-target arthropods. As part of this effort, a symposium was organized for ESA National Meeting entitled "Harmonizing Laboratory Methods to Evaluate Potential Effects of GM Crops on Non-target Arthropods". A follow-up meeting with symposium participants also was organized, which included representatives from universities, USDA-ARS, Environmental Protection Agency, testing laboratories, and seed providers. PARTICIPANTS: Leslie C. Lewis. Professor, USDA Collaborator, USDA-ARS Research Entomologist and Research Leader at the USDA-ARS, Corn Insect and Crop Genetics Research Unit (CICGRU) Richard L. Hellmich, Assistant Professor, USDA Collaborator, USDA Research Entomologist, CICGRU Thomas W. Sappington, Assistant Professor, USDA Collaborator, USDA Research Entomologist, CICGRU Douglas V. Sumerford, Assistant Professor, USDA Collaborator, USDA Research Entomologist, CICGRU Brad S. Coates, USDA Research Geneticists (post-doc), CICGRU Kyung Seok Kim, USDA Research Molecular Biologists (post-doc), CICGRU Nicholas J. Miller, USDA Research Entomologist (post-doc), CICGRU Jarrad R. Prasifka, USDA Research Entomologist (post-doc), CICGRU TARGET AUDIENCES: Customers include agricultural scientists, especially entomologists and corn geneticists, associations of corn producers, producers from big and small farms, crop consultants, organic food producers, gene suppliers (currently Monsanto, Pioneer, Dow AgroSciences, and Syngenta), the U.S. Environmental Protection Agency, the biotechnology division of USDA Animal Plant Health Inspection Service, state agricultural extension specialists, consumers, and students in the agricultural sciences. New customers may include the USDA Natural Resources Conservation Service and sustainable agriculture organizations such as the Leopold Center, Ames IA.

Impacts
Genetic studies were conducted on lab-selected European corn borers that are resistant to Cry1Ab, an insecticidal protein produced by most Bt corn plants. Tests of segregation using genetic markers suggest three candidate genes are not involved, which could indicate novel gene(s) are involved in this resistance trait. These efforts may substantially accelerate efforts to prevent and monitor the development of European corn borer resistance to Bt corn plants. A new method using commercial Bt-seed corn drying bins was investigated for monitoring for European corn borer resistance to Bt corn. While insect movement between bins and high larval mortality may limit the application of sampling beneath drying bins, several modifications could improve the potential utility of the method. The bin monitoring method could increase the efficiency of corn borer resistance monitoring programs. Pitfall traps are commonly used to measure arthropod activity and abundance, although permeable mesh bags filled with plant material, called "litter bags", also have been used. Results from field experiments suggest that the additional effort required to sample with litter bags may be justified for collection of some ground-dwelling taxa. This information provides guidance to improve the design of non-target arthropod field research, especially research that evaluates possible positive or negative effects of transgenic insecticidal crops. Core set of microsatellite markers for western corn rootworm population genetics appications has been adopted and are being used in 2 US, 1 Australian, and 2 European laboratories. European corn borer microsatellite markers and multiplexing protocols are being used in several laboratories in both the U.S. and Europe to study populations. Mark release studies of European corn borer revealed that dispersal of adults from grassy aggregation sites is high regardless of age, sex, or mating status. Flight mill studies with European corn borer indicate that young females engage in true migratory behavior, and that dispersal capacity is high for adults of all ages up to 5 days, and both sexes, whether mated or unmated. Flight behavior of moths infected by the pathogen Nosema is unaffected until a threshold infection level is reached, after which flight activity is severely curtailed.

Publications

  • Bruck, D.J., M.D. Lopez, L.C. Lewis, J.R. Prasifka, and R.D. Gunnarson. 2007. Effects of transgenic Bacillus thuringiensis corn and permethrin on nontarget arthropods. Journal of Agricultural and Urban Entomology 23: 111-124.
  • Coates B.S., Sumerford D.V., Lewis L.C. 2007. A Beta-1,3-galactosyltransferase and brainiac/bre5 homolog expressed in the midgut did not contribute to a Cry1Ab toxin resistance trait in Ostrinia nubilalis. Insect Biochem Mol Biol 37(4): 346-355.
  • Kim, K.S., B.S. Coates, R.L. Hellmich, D.V. Sumerford, and T.W. Sappington. 2007. Isolation and characterization of microsatellite loci from the European corn borer, Ostrinia nubilalis (Hubner) (Insecta: Lepidoptera: Crambidae). Molecular Ecology Notes, Online Early Article, doi: 10.1111/j.1471-8286.2007.01974.x.
  • Kim, K.S., B.W. French, D.V. Sumerford, and T.W. Sappington. 2007. Genetic diversity in laboratory colonies of western corn rootworm (Coleoptera: Chrysomelidae), including a nondiapause colony. Environmental Entomology 36: 637-645.
  • Miller, N. J., M. Ciosi, T. W. Sappington, S. T. Ratcliffe, J. L. Spencer, and T. Guillemaud. 2007. Genome scan of Diabrotica virgifera virgifera for genetic variation associated with crop rotation tolerance. Journal of Applied Entomology 131: 378-385.
  • Reardon, B.J., and T.W. Sappington. 2007. Effect of age and mating status on adult European corn borer (Lepidoptera: Crambidae) dispersal from small-grain aggregation plots. Journal of Economic Entomology 100: 1116-1123.
  • Reardon, K.T., R.L. Hellmich, D.V. Sumerford, L.C. Lewis, B.J. Reardon and D.D. Calvin. 2007. Influence of Plant Severing on Movement of Ostrinia nubilalis Larvae in Zea mays Hybrid Seed Production Fields. Journal of Economic Entomology 100: 1129-1135.
  • Prasifka, J.R., M.D. Lopez, R.L. Hellmich, L.C. Lewis, and G.P. Dively. 2007. Comparison of pitfall traps and litter bags for sampling ground-dwelling arthropods. Journal of Applied Entomology 131: 115-120.
  • Prasifka, J.R., N.P. Schmidt, K.A. Kohler, R.L. Hellmich, M.E. ONeal, and J.W. Singer. 2006. Effects of living mulches on predator abundance and predation on sentinel prey in a corn - soybean - forage rotation. Environmental Entomology 35: 1423-1431.
  • Prasifka, J.R., M.D. Lopez, R.L.Hellmich, and P.L. Prasifka. 2007. Effects of insecticide exposure on movement and population size estimates of ground beetles (Coleoptera: Carabidae). Pest Management Science, online http://www3.interscience.wiley.com/cgi-bin/jissue/104537563, doi: 10.1002/ps.1460.
  • Prasifka, P.L., R.L. Hellmich, J.R. Prasifka, and L.C. Lewis. 2007. Effects of Cry1Ab-expressing corn anthers on the movement of monarch butterfly larvae. Environmental Entomology 36: 228-233.


Progress 01/01/06 to 12/31/06

Outputs
A colony of European corn borers (ECB) was selected for high levels of resistance to the Bt protein Cry1Ab (>3000-fold resistance). Genetic analyses indicate that the resistance is not monogenic and also that the primary mechanisms reported in the literature for Bt resistance do not adequately describe the resistance in this colony of ECB. Mapping populations were generated to isolate other potential genetic mechanisms. Much research has been conducted on the possible effects of genetically-engineered (GE) corn on non-target organisms. Many of these studies, however, ignore influences of plot size. Use of small plots (width < 9 m) for non-target studies on GE crops generally should be avoided because of insect movement among plots. Also, when planning research it is important to consider whether one of the non-target groups being studied is likely to be affected by plot isolation. Results of laboratory flight mill studies support conclusions from field experiments that unmated newly emerged ECB adults are predisposed to make long-distance flights, averaging 6.2 km for females and 1.7 km for males. Moths that have mated, or that are infected with Nosema show a reduced flight propensity.

Impacts
The European corn borer if unchecked causes $50-$150 in losses per hectare. Transgenic Bt corn is revolutionizing management of this insect. Research presented here provides science for development of refuges and extends the life of the transgenic technology.

Publications

  • Coates B.S., D. V. Sumerford, R.L. Hellmich, L.C. Lewis. 2005. Sequence variation in the cadherin gene of Ostrinia nubilalis: A tool for field monitoring. Insect Biochem Mol Biol 35(2):129-139.
  • Coates B.S., R. L. Hellmich, L.C. Lewis. 2005. Polymorphic CA/GT and GA/CT microsatellite loci for Ostrinia nubilalis (Lepidotera: Crambidae). Mol Ecol Notes 5(1):10-12.
  • Coates B.S., R. L. Hellmich, L. C. Lewis. 2005. Two differentially expressed ommochrome- binding protein-like genes (obp1 and obp2) in larval fat body of the European corn borer, Ostrinia nubilalis. 12 pp. J. Insect Sci. 5:19.
  • Coates B.S., R.L. Hellmich, L.C. Lewis. 2006. Sequence variation in trypsin- and chymotrypsin-like cDNAs from the midgut of Ostrinia nubilalis: Methods for allelic differentiation of candidate Bacillus thuringiensis resistance genes. Insect Mol Biol 15(1):13-24.
  • Prasifka, J. R., D. V. Sumerford, R. L. Hellmich, L. C. Lewis, and D. D. Calvin. 2006. Sampling European corn borer (Lepidoptera: Crambidae) larvae from seed corn drying bins for Bt resistance monitoring. Southwestern Entomologist 31:269-279.
  • Prasifka, J. R., N. P. Schmidt, K. A. Kohler, M. E. O'Neal, R. L. Hellmich, J. W. Singer. 2006. Effects of living mulches on predator abundance and sentinel prey in a corn-soybean-forage rotation. Environ. Entomol. 35(5):1423-1431.
  • Reardon, B.J., Sumerford, D.V., Sappington, T.W. 2006. Impact of trap design, windbreaks, and weather on captures of European corn borer (Lepidoptera: Crambidae) in pheromone-baited traps. Journal of Economic Entomology. 99:2002-2009.
  • Reardon, B.J., Sumerford, D.V., Sappington, T.W. 2006. Dispersal of newly-eclosed European corn borer moths (Lepidoptera: Crambidae) from corn into small-grain aggregation plots. Journal of Economic Entomology. 99:1641-1650.


Progress 01/01/05 to 12/31/05

Outputs
To slow development of resistance in the European corn borer (ECB) to transgenic Bt corn, research was conducted to refine refuges. It was determined that newly emerged ECB moths do not disperse to the first available "grassy site" as expected but move beyond to other sites. These data will have implications for placement of refuges. ECB larvae infected with the pathogen Nosema pyrausta and fed a diet containing Bt-corn tissue lost weight in the 4th and 5th instars. If either resistant or susceptible ECB moths are infected with N. pyrausta their fitness may be decreased, compromising the strategy of the refuge to delay development of resistance to Bt corn. The fungus Beauveria bassiana colonizes the corn rhizophere, possibly facilitating the fungus forming an endophyte with corn. F2 families originating from 571 different female ECB moths were screened for resistance to Bt-corn tissue. Several families exhibiting greater larval survival on Bt tissue were observed and saved for genetic evaluation. These results will aid in decisions relevant to resistance management of ECB.

Impacts
The European corn borer if unchecked causes $35-$125 in losses per hectare. Transgenic Bt corn is revolutionizing management of this insect. Research presented here provides science for development of refuges and extends the life of the transgenic technology.

Publications

  • Anderson, P.L., Hellmich, R.L., Prasifka, J.R., Lewis, L.C. 2005. Effects on fitness and behavior of monarch butterfly larvae exposed to a combination of Cry1Ab-expressing corn anthers and pollen. Environmental Entomology. 34:944-952.
  • Prasifka, J.R., Hellmich, R.L., Dively, G.P., Lewis, L.C. 2005. Assessing the effects of pest management on non-target arthropods: the influence of plot size and isolation. Environmental Entomology. 34:1181-1192.
  • Anderson, P.L., Hellmich, R.L., Sears, M.K., Sumerford, D.V., Lewis, L.C. 2004. Effects of Cry1Ab-expressing corn anthers on monarch butterfly larvae. Environmental Entomology. 33:1109-1115.


Progress 01/01/04 to 12/31/04

Outputs
Fields were intensively mapped for first-generation European corn borer damage, and results indicated that first-generation damage is not randomly distributed within a field, but there are hot spots and cold spots. The spatial distribution of moths in grass surrounding the field was not correlated with distribution of damage within the field. Preliminary analyses indicate there was a strong correlation between extended leaf heights and corresponding damage, with taller plants sustaining the most damage, while shorter plants sustained progressively less damage. Potential genes involved in European corn borer resistance to Bt corn were sequenced. This information contributes to a database that will help researchers understand insect resistance mechanisms and help researchers detect resistant insects. A common disease of the European corn borer, Nosema pyrausta, could mask the detection of moths resistant to Bt corn. Sorting out diseased and healthy larvae will improve resistance monitoring methods. This information will benefit all stakeholders interested in sustaining the long-term use of Bt corn.

Impacts
European corn borer is a serious pest in the Corn Belt costing growers yield losses from $35 to $125 per hectare of corn. Transgenic corn hybrids could revolutionize corn borer management, but there are questions concerning insect resistance. Resistance management research will help protect this valuable resource from developing resistant corn borers. Not all growers will opt to plant transgenic corn with insecticidal properties. For these growers to make a profit, a better understanding of the dynamics of indigenous biological control organisms is imperative for providing low-input options for corn production.

Publications

  • Reardon, B.J., Hellmich, R.L., Sumerford, D.V., Lewis, L.C. 2004. Growth, development, and survival of Nosema pyrausta-infected European corn borers (Lepidoptera: Crambidae) reared on meridic diet and Cry1Ab. Journal of Economic Entomology. 97:1198-1201.
  • Coates, B.S., Sumerford, D.V., Hellmich II, R.L., Lewis, L.C. 2004. Partial mitochondrial genome sequences of Ostrinia nubilalis and Ostrinia furnicalis. International Journal of Biological Sciences. 1:13-18
  • Coates, B.S., Hellmich II, R.L. 2003. Two sex-chromosome-linked microsatellit loci show geographic variance among North American Ostrinia nubilalis. Journal of Insect Science. 3:29 p 1-6.
  • Zoerb, A.C., Spencer, T., Hellmich II, R.L., Wright, R.J., Siegfried, B.D. 2003. Larval distribution and survival of second generation European corn borer, Ostrnia nubilalis (Hubner)(Lepidoptera: Crambidae) on event 176 Bt corn. Crop Science. 22:179-184.


Progress 01/01/03 to 12/31/03

Outputs
1) Understanding the molecular bases of insect resistance to transgenic Bt corn will facilitate the development of tests to detect resistant insects. Putative resistance genes from European corn borer midgut have been sequenced. This information will allow researchers to assess resistance gene diversity in Iowa populations of moths, help researchers identify genes associated with resistance, and help preserve Bt as a valuable natural resource. 2) Refuge corn that produces lots of European corn borers susceptible to Bt proteins is essential for delaying corn borer resistance to Bt corn. Certain varieties of corn, such as popcorn, have the potential to help growers with managing insect resistance because they produce more corn borers than field corn. This information will be useful to growers and scientists interested in delaying European corn borer resistance to Bt corn. 3) Beauveria bassiana is an important fungus for the biocontrol of European corn borer. Especially virulent stains of this fungus can be identified with molecular genetic markers. This approach will allow researchers to develop stains of this fungus that could be used by growers as a biocontrol method for controlling European corn borer in Iowa.

Impacts
European corn borer is a serious pest in the Corn Belt costing growers yield losses from $35 to $125 per hectare of corn. Transgenic corn hybrids could revolutionize corn borer management, but there are questions concerning insect resistance. Resistance management research will help protect this valuable resource from developing resistant corn borers. Not all growers will opt to plant transgenic corn with insecticidal properties. For these growers to make a profit, a better understanding of the dynamics of indigenous biological control organisms is imperative for providing low-input options for corn production.

Publications

  • Hunt, T.E., L.G. Higley, J.F. Witkowski, L.J. Young, R.L. Hellmich. 2001. Dispersal of adult European corn borer (Lepidoptera: Crambidae) within and proximal to irrigated and non-irrigated corn. J. Econ. Entomol. 94:1369-1377.
  • Coates B.S., R.L. Hellmich, L.C. Lewis. 2001. A minisatellite from the filamentous ascomycete Beauveria bassiana shows allelic variability independent of host range and geographic origin. Genome 45(1):125-132.
  • Bruck, D.J., L.C. Lewis, R.D. Gunnarson. 2001. Interaction of Nosema pyrausta and temperature on Ostrinia nubilalis egg production and hatch. J. Invertebr. Path. 78:210-214.
  • Hurley, T.M., S. Secchi, B.A. Babcock, R.L. Hellmich. 2002. Managing the risk of European corn borer resistance to Bt corn. Environ. & Res. Econ. 22:537-558.
  • Gatch, E.W., R.L. Hellmich, G.P. Munkvold. 2002. A comparison of maize stalk rot occurrence in Bt and non-Bt hybrids. Plant Disease 86:1149-1155.
  • Pilcher, C.D., M.E. Rice, R.A. Higgins, K.L. Steffey, R.L. Hellmich, J. Witkowski, D. Calvin, K.R. Ostlie, M. Gray. 2002. Biotechnology and the European corn borer: Measuring historical farmer perceptions and adoption of transgenic Bt corn as a pest management strategy. J. Econ. Entomol. 95:878-892.
  • Hurley, T.M., S. Secchi, B.A. Babcock, R.L. Hellmich. 2002. Managing the risk of European corn borer resistance to Bt corn. The Economics of Modeling Environmental Impacts of Agricultural Biotechnologies (T. Swanson, ed.), Kluwer Academic Publishers. p. 171-193.
  • Coates B.S., R.L. Hellmich, L.C. Lewis. 2002. Beauveria bassiana haplotype determination based on nuclear rDNA internal transcribed spacer PCR-RFLP. Mycol. Res. 106(1):40-50.
  • Coates B.S., R.L. Hellmich, L.C. Lewis. 2002. Nuclear small subunit rRNA group I intron variation among Beauveria spp provide tools for strain identification and evidence of horizontal transfer. Curr. Genet. 41:414-424.
  • Bruck, D.J., L.C. Lewis. 2002. Whorl and pollen-shed stage application of Beauveria bassiana for suppression of adult western corn rootworm. Entomologia Experimentalis et Applicata 103:161-169.


Progress 01/01/02 to 12/31/02

Outputs
The European corn borer (ECB), a major pest of corn, is currently managed by chemical insecticides and plant resistance to insect feeding. Reduced use of chemical insecticides is a goal of this research. ECB is considered a secondary pest that must be managed in an areawide program to manage the corn rootworm. Research was conducted at the Corn Insects and Crop Genetics Research Unit, Ames, IA to determine if Slam, an attractant/adulticide for the corn rootworm, could be deployed simultaneously with an egg parasitoid, Trichogramma brassicae. In laboratory research it was determined that Slam did not interfere with the ability of T. brassicae to parasitize ECB eggs, the development of T. brassicae in these eggs, or the emergence of T. brassicae. This research provides a biologically-based tool to manage ECB that occurs within an area where Slam is used to manage the corn rootworm. Transgenic corn hybrids expressing crystal protein endotoxin genes from Bacillus thuringiensis Berliner are an increasingly popular tactic for managing ECB in North America. ECB populations also are often vulnerable to the ubiquitous entomopathogenic microsporidium Nosema pyrausta. We examined the effect of feeding meridic diet incorporated with purified Cry1Ab on growth, development, and survival of Nosema-infected and uninfected neonate ECB. Infected larvae developed more slowly than uninfected larvae. Increasing concentrations of Cry1Ab in diet reduced larval development, and this phenomenon was amplified by microsporidiosis. Infected larvae weighed significantly less than uninfected larvae. The relationship between Nosema infection, Cry1Ab concentration, and larval weight was fitted to an exponential function. The LC50 of infected larvae was about half that of uninfected larvae, indicating that infected larvae are more vulnerable to toxin. This work has implications for resistance management of ECB and demonstrates that it is important to determine whether N. pyrausta is present when testing susceptibility of larvae to some transgenic corn hybrids.

Impacts
Trichogramma brassicae can be used to manage the ECB in the same ecosystem where Slam is being used to manage the western corn rootworm and an indigenous insect pathogen will play a key role in insect resistance management.

Publications

  • Bruck DJ and LC Lewis. 2002. Whorl and pollen-shed applications of Beauveria bassiana for suppression of adult western corn rootworm. Entomol. Exp. Appl. 103:161-169.
  • Bruck DJ and LC Lewis. 2002. Rainfall and crop residue effects on soil dispersion and Beauveria bassiana spread to corn. Applied Soil Ecology 20:183-190.


Progress 01/01/01 to 12/31/01

Outputs
The European corn borer (ECB) is a serious pest in the Corn Belt costing farmers yield losses from $40 to $150 per hectare. Currently, ECB is managed with rescue treatments of chemical insecticides and plant resistance to insect feeding including the use of transgenic plants. Research was conducted to better understand the population genetics of ECB while developing resistance management strategies. Also, the dynamics of Beauveria bassiana was researched as a biological control component. Contiguous 14,535 and 14,536 nucleotide long near complete mitochondrial genome sequences were respectively obtained for two lepidopteran insect species, ECB and Ostrinia furnicalis. Both DNA sequences contain thirteen complete protein coding regions, 21 of 22 tRNA genes, and the lrRNA. Partial sequences from srRNA and tRNA-met genes were recovered, whereas that from the D-loop was not obtained. Gene order was identical to that of Drosophila, except arrangement of the tRNA cluster IQM was unique to Lepidoptera, compared to other published genomes. Sequenced regions of ECB and O. furnicalis were 80.2 and 80.4% A + T, respectively, which represented the highest A + T bias yet reported for analogous insect mitochondrial regions. Mutation analysis indicated a preponderance of synonymous codon changes within protein coding sequences and insertion/deletions in noncoding intragenic spaces. The rRNA and tRNA gene sequences were more highly conserved, outside of a tRNA-Ala and tRNA-Asp region. Carpophilus freemani is a fungivore commonly found in corn, which frequents O. nubilalis tunnels. This study was conducted to determine if C. freemani can vector B. bassiana in the laboratory. C. freemani adults were fed B. bassiana to determine if viable fungi were present in their fecal material. Beetles were also surface contaminated with conidia and placed in artificial ECB tunnels (constructed from excised corn stalks) both with and without ECB larvae to determine if conidia were mechanically transferred. Beetles fed B. bassiana conidia had viable fungus in 14% of their fecal droppings, while none of the fecal droppings collected from control beetles contained viable fungus. Beetles treated with B. bassiana left significantly more colony forming units in the artificial tunnels than control beetles. ECB larvae exposed to artificial tunnels simultaneously with treated beetles or to tunnels from which treated beetles had frequented became infected. Refuge is an important component of a strategy to delay insect resistance to transgenic corn hybrids, because it provides susceptible insects to mate with potential resistant insects. Presently, growers plant a minimum of 20% field corn as a refuge. In this study, popcorn was evaluated for its usefulness as a refuge crop for ECB and the Diabrotica complex. The goal is to provide growers with a refuge option for both insect pests that requires less than 20% of the crop. The effects of several popcorn varieties on ECB density and distribution were investigated on four farms. Results from these experiments show that popcorn can be an efficient refuge for both insect pests.

Impacts
Biological control organisms and transgenic plants are valuable tools for an integrated approach to insect management. These results help define ways to manage resistance to transgenics and also define the genetics of the ECB and define the dynamics of B. bassiana.

Publications

  • Bruck DJ and LC Lewis. 2001. Adult Diabrotica spp. (Coleoptera:Chrysomelidae) infection at emergence with indigenous Beauveria bassiana (Deuteromycotina:Hyphomycetes). J. Invertebr. Pathol. 77:288-289.
  • Lewis LC, DJ Bruck, RD Gunnarson and KG Bidne. 2001. Assessment of plant pathogenicity of endophytic Beauveria bassiana in Bt transgenic and non-transgenic corn. Crop Sci. 41:1395-1400.
  • Showers WB, RL Hellmich, ME Derrick-Robinson and WH Hendrix. 2001. Aggregation and disperal behavior of marked and released European corn borer (Lepidoptera:Crambidae) adults. Environ. Entomol. 30(4):700-710.


Progress 01/01/00 to 12/31/00

Outputs
The European corn borer (ECB) is a serious pest in the Corn Belt costing farmers yield losses from $40 to $150 per hectare. Currently, ECB is managed with rescue treatments of chemical insecticides and plant resistance to insect feeding including the use of transgenic plants. Certain communities are concerned about the impact of transgenics on nontarget organisms. Research was conducted to directly address these concerns and to develop alternative methods to manage ECB. Laboratory tests were conducted to determine whether Bt pollen influences survival and weight of monarch butterfly, Danaus plexippus, larvae. Each larva was presented with two leaf disks from common milkweed, Aesclepias syriaca, in a small petri dish with an agar substrate. Pollen was suspended in water and applied to leaves with a thin layer chromatography sprayer. Three types of Bt pollen (BT11, MON810, and 176) were tested in separate tests. For most tests two of the Bt pollen treatments were compared to no pollen and non-Bt near isoline pollen controls. Several densities of pollen were tested ranging from 5 to nearly 1,500 pollen grains/cm2. Results indicate that the no effect level for 176 pollen was less than 15 pollen grains/cm2. On the other hand, the no effect levels of pollen for BT11, MON810 and Cry1F were greater than 750 pollen grains/cm2 and perhaps higher than 1,000 pollen grains/cm2. Nosema pyrausta, an obligate pathogen, causes reduced fecundity and longevity of ECB. This study was conducted to determine the effect of temperature and N. pyrausta infection on O. nubilalis egg production, hatch and level of infection. In both scenarios, infected and noninfected insects were placed in two different temperature regimes. The first regime allowed moths to oviposit under optimum conditions (27BC, 65% RH, 16:8 (LD)), while moths in the second regime were held at 16 degrees C for one week after which they were moved to optimum conditions to oviposit. Averaged over temperatures, infected females produced 25% fewer eggs than their noninfected counterparts. Cool temperatures alone reduced egg production by 16% when averaged over infected and noninfected moths. Nosema pyrausta infection reduced egg production per female by 53% and 11% in 16 degrees C and 27 degrees C temperature regimes, respectively. Exposure to cool temperatures alone reduced egg production by infected individuals by 50%, while noninfected individuals in cool conditions had only a 5% reduction in egg production. Exposure to cool temperatures during the ovipositional period had a more dramatic impact in reducing egg production in N. pyrausta infected than noninfected ECB.

Impacts
Transgenic corn hybrids and biological control organisms are valuable tools for an integrated approach to insect management. These results help define the impact of the transgenics on nontargets and also define the importance of indigenous organisms on a pest insect.

Publications

  • Giles KL, Hellmich RL, Iverson CT and Lewis LC. 2000. Effects of Transgenic Bacillus thuringiensis Maize Grain on B. thuringiensis - Susceptible Plodia interpunctella (Lepidoptera:Pyralidae). J. Econ. Entomol. 93:1011-1016.
  • Hellmich RL, Higgins LS, Witkowski JF, Campbell JE and Lewis LC. 1999. Oviposition by European Corn Borer (Lepidoptera:Crambidae) in Response to Various Transgenic Corn Events. J. Econ. Entomol. 92:1014-1020.
  • Andow DA, Olson DM, Hellmich RL, Alstad DN and Hutchison WD. 2000. Frequency of Resistance to Bacillus thuringiensis Toxin Cry1Ab in an Iowa Population of European Corn Borer (Lepidoptera:Crambidae). J. Econ. Entomol. 93:26-30.


Progress 01/01/99 to 12/31/99

Outputs
The European corn borer (ECB) is a serious pest in the Corn Belt costing farmers yield losses from $15 to $50 per acre of corn. Currently, ECB is managed using rescue treatments of chemical insecticides, and plant resistance to insect feeding including transgenic plants. Transgenic corn hybrids with a gene from the bacterium Bacillus thuringiensis (Bt) could revolutionize ECB management. Dramatic control of ECB on these plants has many scientists concerned about high selection pressure to toxins in these plants and subsequent adaptation of pest populations. Also, the effect of these transgenic corns on nontarget insects including the monarch butterfly, Danaus plexippus must be addressed. Laboratory tests were conducted to determine whether monarch butterfly larvae, Danaus plexippus, prefer or avoid milkweed leaves with Bt pollen, and to determine whether Bt pollen influences larval weight and survival. Choice and feeding results suggest that monarch larvae are influenced by the presence of pollen. When presented with leaves with no pollen and very high amounts ( 600 grains/cm2) of pollen, more larvae were found on the leaves with no pollen. Weight and survival data indicate that larvae feeding on milkweed leaves with high (150 grains/cm2) and moderate ( 60 grains/cm2) amounts of pollen from the MON810 and CBH351 are not affected. At the very high levels of pollen ( 600 grains/cm2) these same larvae were smaller than larvae from the control treatments, but survival was not different from that of the controls. Larvae feeding on leaves with pollen from the 176 type of corn were affected at each of the pollen density levels. Bt 176 corn represents about 2.5% of total corn planted in the United States. A study was designed to determine the Bt pollen density on milkweed leaves to which monarch larvae might be exposed under natural conditions. The amounts of pollen deposited on milkweed leaves was much less than on slides. On average, milkweed leaves captured only 30% of the pollen available. Our feeding trials with monarch larvae and 2 types of Bt pollen indicated that leaves with pollen densities below 150 grains/cm2 had no effect on larval weight or survivorship. Over all 7 fields and compass directions, the proportion of leaves with pollen densities below 150 grains/cm2 was 80% for leaves at the edge of a corn field (0 meters), 88% at 1 meter, and 100% for 2 meters and beyond. Beyond 8 meters the pollen density on leaves was essentially zero. These results are for pollen deposition under non-rainy conditions. Comparisons of leaves before and after rains indicated that heavy rains reduced the amount of pollen on leaves by about 90%.

Impacts
The data are critical to policy makers to determine the environmental safety of the Bt transgenic corn.

Publications

  • No publications reported this period


Progress 01/01/98 to 12/31/98

Outputs
The European corn borer (ECB) is a serious pest in the Corn Belt costing farmers yield losses from $15 to $50 per acre of corn. Currently, ECB is managed using rescue treatments of chemical insecticides, and plant resistance to insect feeding including transgenic plants. Transgenic corn hybrids with a gene from the bacterium Bacillus thuringiensis (Bt) could revolutionize ECB management. Dramatic control of ECB on these plants has many scientists concerned about high selection pressure to toxins in these plants and subsequent adaptation of pest populations. Resistance management to prevent ECB adaptation to these toxins is necessary to protect this valuable resource. Resistance management for transgenic corn is likely to depend on a refuge strategy complemented by high expression of Bt protein in the plant. There is a critical gap of knowledge, however, concerning corn borer refuge. Trichogramma brassicae, an egg parasitoid, is a very promising biological control. Beauveria bassiana, an entomopathogenic fungus, forms an endophytic relationship with Zea mays but establishment of the fungus is not uniform in all cultivars. Research was conducted to increase ECB production in an agronomic crop. The most successful agronomic crops were sweet corn and popcorn. Various densities of popcorn (1x, 2x, 4x, 6x, 8x, 12x, 16x, 20x) were evaluated for ECB refuge potential. ECB production peaked at the 12x density where ECB production was nearly 21 times greater than some popular field corn varieties. These "sacrificial" plants give producers an option to produce ECB in small areas. Producers could use 1-1.5% of their land to achieve 20-30% normal ECB refuge. Extracts of corn taken at different developmental stages exhibit growth of B. bassiana when the extracts are placed on an agar plate. This indicates that chemicals produced by some cultivars at given growth stages may inhibit B. bassiana from forming an endophytic relationship. Determined that plantings of oats and two varieties of millet give plant densities sufficient to create congregating sites for ECB. Also, ECB will oviposit on these plants. Determined that Trichogramma brassicae will remain in these plots and parasitize ECB eggs. IMPACTS OF RESEARCH: Transgenic corn hybrids, insect pathogens, and parasitoids are valuable tools for an IPM approach to corn insects. Insect resistance management will help prolong the use of the transgenic technology and help meet the goal of 75 percent of the crop acreage under IPM by the year 2000.

Impacts
(N/A)

Publications

  • Hellmich, R.L., Pingel, R.L. and Hansen, W.R. 1998. Influencing European corn borer (Lepidoptera:Crambidae) aggregation sites in small grain crops. Environ. Entomol. 27:253-259.


Progress 01/01/97 to 12/31/97

Outputs
Managing European corn borer (ECB), Ostrinia nubilalis (Hubner), resistance to transgenic corn hybrids probably will require a combination of strategies that will vary regionally. Cultural practices, equipment availability, alternative crops, weed control, aggregation sites, corn hybrid propensities to produce ECB, and baseline ECB populations are some factors that should be considered. Before producers can design specific plans for their farms, they must understand the basic concepts and issues concerning refuge and high dose. The first question addressed in this research is: How can farmers use managed refuge to increase populations of ECB that are susceptible to transgenic toxins? Toward this objective several varieties of sweet corn, popcorn, commercially available field corn, and popcorn planted at various densities (1x, 2x, 4x, 6x, 8x) were evaluated for ECB refuge potential. Preliminary results suggest sweet corn, particularly Silver Queen and Kandy Korn, and popcorn, particularly White Rice and South American, produced the highest numbers of ECB. ECB production increased with popcorn density. Highest number of ECB in the experiment was produced by 8x popcorn. The 22.4 ECB per normal plant area was nearly 25 times greater than some popular field corn varieties. Increasing popcorn density can substantially increase ECB production. Such methods could be used to produce refuge ECB in small well-defined areas. Economic modeling results suggest that managing ECB resistance by using refuge plantings is economically sensible. Nosema pyrausta, a microsporidium is one of the naturally occurring population regulators of ECB. N. pyrausta is density dependent and is transmitted both horizontally and vertically. It causes mortality of neonate larvae, and reduces longevity and fecundity of adults. The planting of B.t.-transgenic corn will likely reduce the number of ECB larvae. The impact of larval reduction on N. pyrausta is not known. Studies were initiated to determine the percentage of ECB infected with N. pyrausta throughout the U.S. Corn Belt. Percentages are: NY - 32; KS - 33; MI - 30; DE - 56; SD - 33; ND - 87; IA - 70; IL - 89; NE - 87; MN - 88. The protocols for managing resistance to transgenic corn and the base-line data on N. pyrausta are being used by extension workers, the EPA, and commercial seed corn producers to develop management programs for ECB.

Impacts
(N/A)

Publications

  • HELLMICH, R.L., PINGEL, R.L., and HANSEN, W.R. 1998. Influencing European corn borer (Lepidoptera:Crambidae) aggregation sites in small grain crops. Environ. Entomol. (In Press).
  • OSTLIE, K.R., HUTCHISON, W.D., and HELLMICH, R.L. 1997. Bt corn and European corn borer. NCR publication 602. University of Minnesota,
  • HURLEY, T.M., BABCOCK, B.A., and HELLMICH, R.L. 1997. Biotechnology and Pest Resistance: An economic assessment of refuges. Working Paper 97--WP 183, Center for Agricultural and Rural Development, Iowa State
  • PINGEL, R.L. and LEWIS, L.C. 1997. Field application of Bacillus thuringiensis and Anagrapha falcifera multiple nucleopolyhedrovirus against the corn earworm (Lepidoptera:Noctuidae). J. Econ. Entomol.


Progress 01/01/96 to 12/30/96

Outputs
Managing European corn borer (ECB), Ostrinia nubilalis, resistance to transgeniccorn hybrids will rely on a refuge strategy. Candidate crops for first-generation ECB refuge (Bay oats & proso millet) and second-generation ECB refuge (proso millet) have been identified. Refuge values of these crops compared with non-transgenic corn are high. Trichogramma brassicae released at 300 Trichocaps (ca. 600 wasps/Trichocap) per ha in 1, 2 or 3 releases resulted in 83.3 percent parasitization of ECB egg masses and 1.5 cm of tunneling per plant; 71.6 percent parasitization of ECB egg masses and 1.5 cm tunneling per plant; and 51.5 percent parasitization of ECB egg masses and 2.4 cm of tunneling per plant. The plant terpenoid farnesal was shown to be a deterrent for oviposition of the European corn borer in laboratory as well as field tests. However, farnesal is slightly phytotoxic. No detrimental effects were observed in the abundance of ECB predators (coccinellids, anthocorids, chrysopids) in Bt corn compared with non-Bt corn. Predator numbers observed before, during and after pollen shed suggest that Bt corn pollen will not affect natural enemy movement in corn.

Impacts
(N/A)

Publications

  • BINDER, B.F. and ROBBINS, J.C. 1996. Age- and density-related oviposition behavior of the European corn borer, Ostrinia nubilalis (Lepidoptera:Pyralidae).J. Insect Behavior 9:755-769.
  • LEWIS, L. C., et al. 1996. Aptness of insecticides (B. thuringiensis and carbofuran) with endophytic B. bassiana, in suppressing larval populations of the European corn borer. Agric., Ecosystems & Environ. 57:27-34.
  • MUNKVOLD, G.P., HELLMICH, R.L., SHOWERS W. B., and RICE, M.E. 1996. Gibberella infection in kernels of transgenic (Bt) maize. Phytopathology 86:S47.
  • PILCHER, C.D., OBRYCKI, J.J., RICE, M. E., and LEWIS, L.C. 1997. Preimaginal development, survival, and field abundance of insect predators on transgenic Bacillus thuringiensis corn. Env. Entomol. (In press) PINGEL, R.L. and LEWIS, L.C. 1996. The fungus Beauveria bassiana (Balsamo) Vuillemin in a corn ecosystem: its effect on the insect predator Coleomegilla maculata De Geer. Biol. Contr. 6:137-141.


Progress 01/01/95 to 12/30/95

Outputs
The preimaginal developmental time was longer for Coleomegilla maculata fed ECB eggs than for C. maculata fed on pea aphids. Pollen from Bacillus thuringiensis-transgenic corn does not appear to negatively impact the survival to the adult stage of twelvespotted lady beetles, minute pirate bugs or green lacewings. In laboratory bioassays to test terpenoids and related compounds as ovipositional deterrents for ECB the sesquitepenoid farnesal was the most active analog. The sesquiterpene structural isomers farnesene and humulene, however, attracted females. A study was conducted to investigate ways to influence ECB aggregation sites with small grain crops. Barley interplanted with alfalfa or crimson clover attracted more ECB moths than a no legume control. Number of moths increased as plant canopy increased. Farmer-managed oat fields also were evaluated. ECB adults were particularly attracted to high density patches of oats or oats that were interplanted with alfalfa. A laboratory experiment was conducted to simulate the effect of cool damp conditions and Nosema pyrausta on egg production by ECB. A N. pyrausta-infected population placed immediately in the oviposition regime produced 67% fewer eggs than the noninfected population placed immediately in the oviposition regime; the infected population held for one week at 16 deg. C produced 70% fewer eggs than the noninfected population held under the same conditions.

Impacts
(N/A)

Publications

  • BINDER, B.F., ROBBINS, J.C. and WILSON, R.L. 1995. Chemically mediate ovipositional behaviors of the European corn borer, Ostrinia nubilalis (Lepidoptera:Pyralidae). J. Chem. Ecol. 21:1315-1327.


Progress 01/01/94 to 12/30/94

Outputs
Prairie grasses at borders of corn fields seemingly are being used by Ostrinia nubilalis (Hubner) moths as action sites thereby increasing larval density in field edges, thus the beneficial effects of increased parasitism by the wasp Macrocentrus grandii was offset by higher borer infestation. Field studies to test transgenic corn containing Bacillus thuringiensis Cry toxins on European corn borer were conducted. A transgenic corn hybrid presented by Monsanto was protected whorl to harvest and yielded similarly to the same isogenic hybrid that had been protected with weekly applications of a pyrethroid. The transgenic hybrid yielded approximately 31.6 qu/ha more than the unprotected isogenic hybrid. In determining the presence of predator species, different plant development stages were more important than whether a corn hybrid developed by CIBA was transgenic or isogenic. A field study to test the effect of a natural botanical, azadiractin, on O. nubilalis oviposition was confounded by the emulsifier also reducing oviposition.

Impacts
(N/A)

Publications

  • SHOWERS, W.B. 1993. Diversity and variation of European corn borer populations. IN K.C. Kim and B.A. McPheron (eds.). Evolution of insects pests/patterns of variation. John Wiley & Sons, Inc.


Progress 01/01/93 to 12/30/93

Outputs
Heavy rainfall during the crop season in Iowa took a heavy toll on field research. One study in which 300,000 of the parasitic wasp, Trichogramma maidis formulated in Trichocaps, were released to prevent damage by European corn borer to anthesis stage corn showed promise. Egg mass scouting indicated 214 of 260 egg masses were parasitized (82 percent). A natural botanical , azadiractin, from the seed of the neem tree, Azadiractia indica, was tested in the laboratory to determine whether inhibitory pressures on the ovipositional response of European corn borer females could be demonstrated. Size and numbers of egg masses were observed. A significant (t 05 = 2.45) reduction in surface area covered by egg masses was achieved with percentage concentrations of 0.031 to 0.25 azadiractin.

Impacts
(N/A)

Publications

  • MEIGHAN, D.L. 1993. Diapause termination of European corn borer, Ostrinia nubilalis (Hubner), populations in Iowa. M.S. Thesis, Iowa State University, Ames 55 pp.


Progress 01/01/92 to 12/30/92

Outputs
Development of individuals from two populations of European corn borer, eastern North Dakota and central Iowa, on corn representing hybrids from 1950 to 1990 suggest that the North Dakota population survives better on all hybrids tested. These results might be related to the Iowa population coming from parents that were F 9 in the laboratory and the North Dakota population being issued from feral parents. If true, these results contradict the literature pertaining to viability of laboratory reared European corn borer. Also, European corn borer populations were collected in the spring at 90 deg. 30'W longitude and 39 deg. 30'N to 43 deg. 30'N latitudes, and characterized on time required to terminate diapause. Northern populations terminated diapause earlier than southern populations. This phenomenon was inherited in subsequent laboratory reared F 2 and F 3 generations.

Impacts
(N/A)

Publications

  • SHOWERS, W. B. 1993. Diversity and variation of European corn borer populations, Chapter XIV. In: K. C. Kim (ed.) Evolution of Insect Pests. John Wiley and Sons, New York, NY. Accepted 12/11/92.


Progress 01/01/91 to 12/30/91

Outputs
In an attempt to characterize European corn borer populations for diapause termination, during spring, diapausing larvae were collect 91 d 37'W to 95 d 34'W longitudes and 40 d 44'N to 43 d 22'N latitudes. At 95 d 34'W longitude, Missouri River Valley populations broke diapause and developed to adulthood 2.64 days sooner than did adjacent upland populations. This valley phenomenon, seemingly, is similar to one reported for European corn borer populations of the South Saskatchewan River Valley of Alberta. A 4-m wide vacuum developed for vegetable crops (Sukup Mfg. Co., Sheffield, IA) was used to vacuum European corn borer moths from mating sites in foxtailgrass within or adjacent to two of three fields with similar corn hybrid and planting dates. Prevacuuming counts of moths averaged 15 per 10m(superscript 2). Postvacuum counts averaged 3 moths per 10m(superscript 2). Moth numbers 5 days postvacuum remained at 4 per 10m(superscript 2), however, in the unvacuumed action site moths averaged 25 per 10m(superscript 2). Egg masses in fields adjacent to vacuumed waterways remained at 0.04 per corn plant (six, 20 plant samples per field). Masses in the field adjacent to unvacuumed waterways increased from 0.06 per corn plant to 0.28 per corn plant.

Impacts
(N/A)

Publications

  • CALVIN, D.D. et. al., SHOWERS, W.B. et. al. 1991. Similarities in developmental rates of geographically separate European corn borer (Lepidoptera: Pyralidae) populations. Environ. Entomol. 20:441-449.
  • DERRICK, M.E. and SHOWERS, W.B. 1991. Comparison of an adult and larval control strategy for the European corn borer (Lepidoptera: Pyralidae) in seed corn. J. Kans. Entomol. Soc. 64:185-192.
  • SHOWERS, W.B. 1991. Interregional research in resolving some insect pest problems of the Corn Belt, pp. 199-202. In J. Adams, ed. , Insect Potpourri: Adventures In Entomology. Sandhill Crane Press, Gainesville, FL.