Progress 07/01/07 to 06/30/12
Outputs
OUTPUTS: Field and lab studies were conducted to characterize the potential effects of Bt toxins expressed in corn rootworm-protected transgenic corn events on key life history traits of the target pest Diabrotica virgifera virgifera. Results indicate that there can be fitness costs associated with survival on rootworm-protected Bt hybrids; however, fitness costs vary with event(or pyramids of multiple events). Completed a study to determine how adult food quality will impact the fitness of late emerging D. v. virgifera adults reared as larvae on event MON88017(Cry3Bb1 protein) vs. a nontransgenic isoline. Key results: Adult emergence was delayed for adults emerging from MON88017 relative to emergence from a nontransgenic isoline. Cry3Bb1 alone in larval/adult diet or as an interactive factor with adult diet phenology significantly reduced fitness. In one or more experiments,adult size,longevity and/or fecundity were reduced. Phenology of adult diet appeared to be a dominant factor that determined the severity of sublethal effects; a maturing R3-R6 stage corn diet greatly reduced fecundity and longevity. The biology, ecology, and genetics of the sibling species D. barberi (pest) and D.longicornis (non-pest) and potential role of hybrids were studied. Confirmed that there is unidirectional incompatibility between species, but demonstrated that there are no significant fitness costs associated with the fertile female D. longicornis x male D.barberi hybrids, hybrid x hybrid, and parental x hybrid backcrosses. Genetic(AFLP data)and morphological data provided evidence for introgression between D.barberi and D.longicornis. A study was completed to document the frequency of the extended diapause trait within and among D.barberi populations collected throughout the range of D.barberi in Nebraska. Results indicate that there was significant variation in the frequency of extended diapause within and among populations. The highest frequency of extended diapause occurred in a north-south transect that parallels the Missouri River. D.barberi populations collected farther west from the north-south transect exhibited lower frequencies of extended diapause. Results have been disseminated through discussions/presentations at professional meetings, research publications,and extension outlets such as presentations, newsletters, and the press. PARTICIPANTS: PI: Lance J. Meinke. Worked with many collaborators on the project from various Land-grant universities and USDA labs. Many collaborators were members of the NCCC46 Regional Committee. Also collaborated with most major industry groups that are registrants of rootworm-protected Bt corn events. Three graduate students were trained and conducted research that addressed one or more of the project objectives during the life of the project. TARGET AUDIENCES: Target audiences served by this project included industry, academics, regulatory agencies (e.g. EPA), USDA scientists, ag-consultants, and farmers. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
Results of Diabrotica fitness studies have been used by industry, regulatory, and academic scientists as part of the biological data base needed to develop realistic resistance simulation models and sustainable rootworm management practices, to optimize IRM refuge strategies(refuge size, seed blend strategy),and to shift refuge policy in U.S. regulatory agencies. Adoption of rootworm-protected transgenic plants continues to increase so it will be increasingly important to incorporate these new technologies into sustainable management programs, delay potential resistance evolution, and to sustain grower profitability. Sharing of Bt corn data with consultants and growers has affected changes in attitudes and strategies used to manage rootworms in Nebraska. Research on D. longicornis and D. barberi demonstrates that hybridization most likely occurs under field conditions, and that the relative fitness of hybrids of a D. longicornis mother and D. barberi father is comparable to the parental taxa. Introgression into parental populations could potentially affect the behavior and pest status of parental populations in the sympatric area. Results of the D. barberi diapause study contribute to our knowledge of diapause within Diabrotica, provides another example of genetic variation that can occur among D. barberi populations on a relatively small scale, and adds to the database needed to develop appropriate rootworm management strategies for areas of Nebraska.
Publications
- Clark, T. L., D. L. Frank, B. W. French, L. J. Meinke, D. Moellenbeck, T. T. Vaughn, and B. E. Hibbard. 2012. Mortality impact of MON863 transgenic maize roots on western corn rootworm larvae in the field. J. Appl. Entomol. 136: 721-729.
|
Progress 10/01/10 to 09/30/11
Outputs
OUTPUTS: As part of a larger effort to more clearly understand the biology and pest potential of the northern corn rootworm, Diabrotica barberi Smith and Lawrence in Nebraska, a study was conducted to document the frequency of the extended diapause trait within and among D. barberi populations collected throughout the range of D. barberi in Nebraska. This was in response to observations of increasing densities of D. barberi in corn and soybean in eastern Nebraska and unexpected high densities of D. barberi emerging from first-year corn in some counties where the phenomena had not been observed before. Eggs were obtained from female D. barberi collected from locations in eastern Nebraska during both 2008 and 2009. Egg hatch data obtained over two years from each collected population indicate that the extended diapause trait is present in all populations. There was significant variation in the frequency of extended diapause among populations. In general, results were consistent within locations over collection years and the highest frequency of extended diapause occurred in a north-south transect that parallels the Missouri River. D. barberi populations collected farther west from the north-south transect exhibited lower frequencies of extended diapause. To date, results from this study have been disseminated through discussions/presentations at professional meetings. An interdisciplinary study has been initiated to investigate the potential impact of volunteer corn on soybean yield, plant disease, and corn rootworm (western corn rootworm, Diabrotica virgifera virgifera LeConte and northern corn rootworm, D. barberi), population dynamics. The rootworm portion of the project is focusing on the complex interaction of volunteer corn density, volunteer removal timing, and corn rootworm behavior to determine how volunteer corn may contribute to potential corn rootworm injury in first year corn the following year. Preliminary data from 2011 indicate that small patches of R1-R2 stage volunteer corn were highly attractive to gravid D. barberi females and that most adults were found on volunteer corn and few on surrounding soybean. PARTICIPANTS: Nothing significant to report during this reporting period. TARGET AUDIENCES: Nothing significant to report during this reporting period. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
Results from this project add to our knowledge of D. barberi biology and ecology and will contribute to the database needed to develop appropriate D. barberi management recommendations for different areas of Nebraska. This work also increases our knowledge of diapause within Diabrotica and provides another example of genetic variation that can occur among D. barberi populations on a relatively small scale. The impact of volunteer corn in soybean on corn rootworm population dynamics will potentially affect the level of larval injury in first corn. This will contribute to the overall risk associated with volunteer corn and will be included in future recommendations pertaining to management of volunteer corn in soybean.
Publications
- Campbell, L. A., T. L. Clark, P. Clark, L. J. Meinke, and J.E. Foster. 2011. Field introgression of D. barberi Smith and Lawrence and D. longicornis (Say) (Coleoptera: Chrysomelidae) based on genetic and morphological characters. Ann. Entomol. Soc. Am. 104: 1380-1391.
- Geisert, R. W. 2011. Frequency of extended diapause in Nebraska populations of Diabrotica barberi Smith and Lawrence. M.S. Thesis. University of Nebraska-Lincoln.
- Pan, Z., D. W. Onstad, T. M. Nowatzki, B. H. Stanley, L. J. Meinke, J. L. Flexner. 2011. Western corn rootworm (Coleoptera: Chrysomelidae) dispersal and adaptation to single-toxin transgenic corn. Environ. Entomol. 40: 964-978.
|
Progress 10/01/09 to 09/30/10
Outputs
OUTPUTS: As part of a larger effort to more clearly understand the biology and pest potential of the northern corn rootworm, Diabrotica barberi Smith and Lawrence in Nebraska,an ongoing study is being conducted to document the frequency of the extended diapause trait within and among D. barberi populations collected throughout the range of D. barberi in Nebraska. This was in response to observations of increasing densities of D. barberi in corn and soybean in eastern Nebraska and unexpected high densities of D. barberi emerging from first-year corn in some counties where the phenomena had not been observed before. To date, egg hatch data obtained over two years from populations collected in eastern Nebraska indicate that the extended diapause trait is present in all populations. There also appears to be significant variation in the frequency of extended diapause among populations. In general, the highest frequency of extended diapause occurred in a north-south transect that parallels the Missouri River. D. barberi populations collected farther west from the north-south transect exhibited lower frequencies of extended diapause. To date, results from this study have been disseminated through discussions/presentations at professional meetings. PARTICIPANTS: Nothing significant to report during this reporting period. TARGET AUDIENCES: Nothing significant to report during this reporting period. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
Results from this project add to our knowledge of D. barberi biology and ecology and contribute to the database needed to develop appropriate D. barberi management recommendations for different areas of Nebraska. This work also increases our knowledge of diapause within Diabrotica and provides another example of genetic variation that can occur among D. barberi populations on a relatively small geographic scale.
Publications
- Onstad, D.W., and L.J. Meinke. 2010. Modeling evolution of Diabrotica virgifera virgifera (Coleoptera: Chrysomelidae) to transgenic corn with two insecticidal traits. J. Econ. Entomol. 103: 849-860.
- Campbell, L.A. and L. J. Meinke. 2010. Fitness of Diabrotica barberi, Diabrotica longicornis, and their hybrids (Coleoptera: Chrysomelidae). Ann. Entomol. Soc. Am. 103: 925-935.
- Campbell, L.A. 2009. Biology and behavior of Diabrotica barberi Smith and Lawrence, Diabrotica longicornis (Say), and hybrids (Coleoptera: Chrysomelidae): characterization of field introgression, and a reevaluation of the taxonomic status of parental taxa. Ph.D. Dissertation, University of Nebraska - Lincoln.
|
Progress 10/01/08 to 09/30/09
Outputs
OUTPUTS: Studies are being conducted to characterize the potential effects of Bt toxins expressed in corn rootworm-protected transgenic corn events on key life history traits of the target pests Diabrotica virgifera virgifera and D. barberi. The relative fitness of adults that emerge from various events (or stacks of multiple events) and associated isolines (refuge) are being characterized so that reliable predictions can be made about the potential genetic contribution these individuals may make to the subsequent generation and their ability to function in a resistance management program. To date, results indicate that there can be substantial fitness costs associated with survival on a rootworm-protected Bt hybrid; however, fitness costs vary with event. Completed a study to determine how adult food quality will impact the fitness of late emerging D. v. virgifera adults reared as larvae on event MON88017 (Cry3Bb1 protein) vs. a nontransgenic isoline. Key results: Adult emergence was delayed for adults emerging from MON88017 relative to emergence from a nontransgenic isoline. Cry3Bb1 alone in larval/adult diet or as an interactive factor with adult diet phenology significantly reduced fitness. In one or more experiments, adult size, longevity and/or fecundity were reduced. Phenology of adult diet appeared to be a dominant factor that determined the severity of sublethal effects; a maturing R3-R6 stage corn diet greatly reduced fecundity and longevity. The biology, ecology, and genetics of the sister species D. barberi (pest) and D. longicornis (non-pest) and potential role of hybrids are being studied. Confirmed that there is unidirectional incompatibility between species, but demonstrated that there are no significant fitness costs associated with the fertile female D. longicornis x male D. barberi hybrids, hybrid x hybrid, and parental x hybrid backcrosses. Studies of pheromone response, mating behavior, and spermatophore size demonstrated that F1 hybrids (D. longicornis mother, D. barberi father) are reproductively fit and also that the two parental taxa exhibit numerous small differences in reproduction. Genetic (AFLP data) and morphological data provided evidence for introgression between D. barberi and D. longicornis. Gene flow between the two taxa appeared to be relatively high, which prevented strong differentiation of populations. PARTICIPANTS: Nothing significant to report during this reporting period. TARGET AUDIENCES: Nothing significant to report during this reporting period. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
Results of Diabrotica fitness studies are being directly used by industry and academic scientists as part of the biological data base needed to develop realistic resistance simulation models, sustainable rootworm management practices and to optimize resistance management strategies. Adoption of rootworm-protected transgenic plants continues to increase so it will be increasingly important to incorporate these new technologies into sustainable management programs, delay potential resistance evolution, and to sustain grower profitability. Research on D. longicornis and D. barberi demonstrates that hybridization most likely occurs under field conditions, and that the relative fitness of hybrids of a D. longicornis mother and D. barberi father is comparable to the parental taxa. Currently available data support a reevaluation of the current taxonomic status of the taxa; redesignation of the taxa as subspecies may be most appropriate. Introgression into parental populations could potentially affect the behavior and pest status of parental populations in the sympatric area.
Publications
- Meinke, L.J., T.W. Sappington, D.W. Onstad, T. Guillemaud, N. J. Miller, J. Komaromi, N. Levay, L. Furlan, J. Kiss, and F. Toth. 2009. Western corn rootworm (Diabrotica virgifera virgifera LeConte) population dynamics. J. Agric. and Forest 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. J. Agric. and Forest Entomol. 11: 47-60.
- Young, S.T. 2009. Effect of Monsanto corn event MON88017, adult diet, and host phenology on selected western corn rootworm, Diabrotica virgifera virgifera LeConte, life history traits. M.S. Thesis. University of Nebraska - Lincoln.
|
Progress 10/01/07 to 09/30/08
Outputs
OUTPUTS: Studies are being conducted to characterize the potential effects of Bt toxins expressed in corn rootworm-protected transgenic corn events on key life history traits of the target pests Diabrotica virgifera virgifera and D. barberi. This is part of a larger effort to determine if there are fitness costs associated with corn rootworm survival on Bt events. An ongoing series of experiments is addressing the interaction of potential D. v. virgifera fitness costs associated with exposure to event MON88017 (Cry3Bb1) and variable adult diet with particular emphasis on beetles that emerge late in the season. The biology, ecology, and genetics of the sibling species D. barberi (pest) and D. longicornis (non-pest) and potential role of hybrids are being studied. Confirmed that there is unidirectional incompatibility between species, but demonstrated that there are no significant fitness costs associated with the fertile female D. longicornis x male D. barberi hybrids, hybrid x hybrid, and parental x hybrid backcrosses. Determined that spermatophore size is inherently greater in D. longicornis than D. barberi. Studies are being conducted to develop a greater understanding of the relationship between D. barberi densities and potential injury to first year corn in eastern Nebraska. Surveys in first year corn indicated that at the field level, a significant relationship between mean adult density and mean root injury occurred during 2006 and 2007, but root injury in many fields was below the level that would potentially cause economic loss. Data from D. barberi first-year corn surveys were shared directly with county educators, consultants, industry reps and growers. Results were presented at Crop Protection Clinics, and county level corn-soybean meetings. During 2008, a study was initiated to document the frequency of the extended diapause trait within and among D. barberi populations collected throughout the range of D. barberi in Nebraska. PARTICIPANTS: Nothing significant to report during this reporting period. TARGET AUDIENCES: Nothing significant to report during this reporting period. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
Results of D. v. virgifera life history and fitness studies will contribute to the biological database that is needed to optimize resistance management strategies, and facilitate estimation of potential F1 population densities that are produced from rootworm-protected and non-protected transgenic events. Biofuel driven increases in continuous corn production may lead to greater rootworm densities in some areas and continued adoption of rootworm-protected transgenic plants. Therefore, it is important to incorporate these new technologies into sustainable management programs, delay potential resistance evolution, and sustain grower profitability. Data from D. barberi first-year corn surveys was used by various clientele when making rootworm management decisions for their geographic location in 2007-2008. If D. longicornis female x male D. barberi hybridization is occurring in eastern Nebraska and eastern Kansas, then introgression into parental populations could potentially affect the behavior and pest status of parental populations in the sympatric area. This could ultimately affect management of D. barberi in some areas.
Publications
- Becker, S.B., and L.J. Meinke. 2008. A technique to morphologically differentiate larvae of Diabrotica virgifera virgifera and D. barberi (Coleoptera: Chrysomelidae). J. Kansas Entomol. Soc. 81: 77-79.
|
Progress 10/01/06 to 09/30/07
Outputs
Studies are being conducted to characterize the potential effects of Bt toxins expressed in corn rootworm-protected transgenic corn events on key life history traits of the target pests Diabrotica virgifera virgifera and D. barberi. This is part of a larger effort to determine if there are fitness costs associated with corn rootworm survival on Bt events. Initial work has been conducted with event MON 863 (Cry3Bb1) although experiments are ongoing with other corn events. D. v. virgifera reared on corn plants expressing Cry3Bb1(event MON 863)developed slower, adult emergence was delayed and sex ratio of emerged beetles became skewed more toward females compared to a non-transgenic isoline. Lifetime dietary exposure of D. v. virgifera to event MON 863 may also result in reduced fecundity. The biology, ecology, and genetics of the sibling species D. barberi (pest) and D. longicornis(non-pest)and potential role of hybrids are being studied. Confirmed that there is
unidirectional incompatibility between species, but demonstrated that female D. longicornis x male D. barberi hybrids, hybrid x hybrid, and parental x hybrid backcrosses all produce fertile offspring. Documented that there are no significant fitness costs associated with the fertile crosses when compared to the parental species. Initiated studies to develop a greater understanding of the relationship between D. barberi densities and potential injury to first-year corn in eastern Nebraska. This was in response to observations of increasing densities of D. barberi in corn and soybean in eastern Nebraska. Surveys in first year corn indicated that at the field level, a significant relationship between mean adult density and mean root injury occurred during 2006 and 2007. The geographic location of the highest and lowest rootworm densities was also consistent over the two year period. Root injury in many fields was below the level that would potentially cause economic loss.
Impacts
Results of D. v. virgifera life history and fitness studies will contribute to the biological database that is needed to optimize resistance management strategies, and facilitate estimation of potential F1 population densities that are produced from rootworm-protected and non-protected transgenic events. Biofuel driven increases in continuous corn production may lead to greater rootworm densities in some areas and continued adoption of rootworm-protected transgenic plants. Therefore, it is important to incorporate these new technologies into sustainable management programs, delay potential resistance evolution, and sustain grower profitability. 2006 data from D. barberi first-year corn surveys were shared directly with county educators, consultants, industry reps and growers. Results were presented at Crop Protection Clinics, and county level corn-soybean meetings. This information was used by various clientele when making rootworm management decisions for their
geographic location in 2007. If female D. longicornis x male D. barberi hybridization is occurring in eastern Nebraska and eastern Kansas, then introgression into parental populations could potentially affect the behavior and pest status of parental populations in the sympatric area.
Publications
- Clark, P. L., T. T. Vaughn, L. J. Meinke, J. Molina-Ochoa and J. E. Foster. 2006. Diabrotica virgifera virgifera (Coleoptera: Chrysomelidae) larval feeding behavior on transgenic maize (MON 863) and its isoline. J. Econ. Entomol. 99: 722-727.
- Campbell, L. A., and L. J. Meinke. 2006. Seasonality and adult habitat use by four Diabrotica species at prairie-corn interfaces. Environ. Entomol. 35: 922-936.
- Nowatzki, T.M., X. Zhou, L.J. Meinke, T. Vaughn, and B.D. Siegfried. 2006. Effect of Bacillus thuringiensis Cry3Bb1 protein on the feeding behavior and longevity of adult western corn rootworms (Coleoptera: Chrysomelidae). J. Econ. Entomol. 99: 927-930.
- Becker. S.C. December 2006. Stage-specific development and mortality of Diabrotica virgifera virgifera LeConte reared on transgenic corn event MON 863 vs. a non-transgenic isoline. M.S. Thesis. University of Nebraska - Lincoln.
- Hunt, T. E., L. J. Meinke, R. J. Wright, and K. J. Jarvi. 2007. Northern corn rootworm in Nebraska: Year one of an adult emergence study. pp. 50-54, Proceedings of Crop Protection Clinics, University of Nebraska Extension, Lincoln.
|
|