Progress 07/01/04 to 06/30/09
Outputs
OUTPUTS: The most important insect pests of corn in Iowa are the corn rootworms. A management concept that had shown preliminary management potential was the coordinated scouting and suppression of adult population over an extended, contiguous range. Sixteen-square-mile research sites were identified and managed in Illinois/Indiana, Iowa and Kansas. The project was subcontracted from the USDA-ARS. Sentinel traps were tested to detect adult beetle emergence and a developmental model was build to predict the emergence of adults so that chemical treatments could be applied at the beginning of oviposition. Fields were scouted for adult beetle activity from July through September and treatments were repeated if necessary. This project was concluded at the beginning of this CRIS project. Results were distributed to farmers at regional Extension meetings and at the annual Integrated Crop Management meeting. A strain of the northern corn rootworm has been selected for that has a 2-year lifecycle and a variety of the western corn rootworm has developed that will lay eggs in crops other than corn. This variant defeats crop rotation because the eggs are present when corn is planted the following year. By 2006 the variant western corn rootworm was reported at the Mississippi River and a project was begun to determine if it was present in Iowa. Emergence traps were placed in corn planted after soybeans to identify infested fields and sticky traps were used in adjacent soybean fields to scout for infested areas in eastern Iowa. The western corn rootworm was discovered in Central Europe in 1992. These countries cannot afford insecticides to control it, but crop rotation is more common. Under this project we evaluated commercial, corn germplasm for tolerance to corn rootworm larval injury. Commercial varieties from Croatia and Serbia were tested in Iowa on infested fields and a companion project was coordinated with the USDA-ARS laboratory in Missouri where the plots were artificially infested with corn rootworms. Corn seed producers had reported that the grape colaspis was causing injury to their seed corn planted after soybeans. Replicated trials were conducted in the infested area to determine if economically damaging populations could be predicted. Some black cutworms will survive on the genetically engineered, lepidopteran resistant YieldGard. Replicated trials were used to determine if these cutworms would attack YieldGard corn after a herbicide was applied to control weeds. Insecticide efficacy and the new transgenic corn varieties that are resistant to corn rootworms were evaluated annually under heavy corn rootworm larval populations. A constant watch for control failures was maintained. Fields of rootworm-resistant, genetically modified corn that appeared to suffer unusually severe larval root injury were visited to verify that they had suffered rootworm larval injury and to try to determine if there was a breakdown in the resistance. PARTICIPANTS: Tollefson, Jon and Gassmann, Aaron, Principal Investigators: Project development and research coordination personnel recruitment and supervision, data analysis and summarizing, and reporting results. Stockdale, Harold and Berry, Edward, Research Associates: Coordinated the Area-Wide Corn Rootworm Project. Prasifka, Patricia, Post-Doctoral Fellow, Kiley, Nicholas, and Dunbar, Michael, Graduate Research Assistants: Developed, executed and reported research on the rotation-resistant corn rootworms. Rynerson, Melissa, Graduate Research Assistant: Surveyed corn fields for naturally occurring pathogens of corn rootworm. Park, Yong-Lak, Graduate Research Assistant: Measured the distribution of corn rootworms in cornfields. Oleson, James and Weber, Pat, Research Specialists: Contracted research with plant protection industries. Designed and executed research protocols and conducted research on plant protectorates. Collected, summarized and reported data from the plant protection trials. Kadlicko, Stephanie, Graduate Research Assistant: Coordinated corn rootworm tolerance research with Serbian entomologist and corn breeder. Conducted the research, collected and analyzed the tolerance data and reported the results in her M.S. thesis. Hibbard, Bruce, Research Scientist, USDA-ARS, Columbia, MO: Conducted the infested evaluations of Croatian and Serbian varieties. Baca, Franja, Entomologist and Stankovic, Goren, corn breeder, Collaborators: Research Scientists from the Maize Research Institute, Belgrade, Serbia. Ivezic, Marija, Collaborator: University of J.J. Strossmayer, Osijek, Croatia. The collaborators chose and provided seed for the corn lines that the institute wanted screened for tolerance or resistance to the corn rootworms. Kaeb, Benjamin, Graduate Research Assistant: Conducted the grape colaspis detection and control experiments. Schmidt, Nina, Graduate Research Assistant: Designed and conducted the black cutworm on YieldGard research. TARGET AUDIENCES: Target audiences include the scientific research community, Extension specialists, farmers, lawmakers, and the general public, as they are interested. Research results were published in refereed journals. Data from the experiments were disseminated in oral presentations at: 1) presentations on corn rootworm management at Field Extension Education Lab field days, 2) Iowa Field Crop Agronomists in-service training, 3) Crop Advantage Series meetings, and 4) weekly state-wide conference calls with Extension Agronomists. Electronic presentations were made in the Integrated Crop Management Newsletter and PowerPoint graphics provided to Extension entomologists and field agronomists for use in their client meetings. PROJECT MODIFICATIONS: The initial treatment threshold in area-wide management rootworm program was 3/4 of a beetle per plant with 1/2 beetle per plant used as the guide line for when a second treatment should be applied. Using these thresholds there was economic injury in some of the fields. As a result, the initial treatment threshold was reduced to 1/2 beetle per plant.
Impacts
On the average, root protection in the beetle area-wide management program was as good as the protection provided by insecticides applied to the soil at planting. The root protection provided by the beetle management program was more variable, however, with some fields not having any detectable injury and a few that suffered severe injury. Soil insecticide-treated fields never achieved such a high level of protection, but they never suffered as much damage either. The adult emergence model reduced sampling costs by half: from 8 to 10 visits to the fields to four. If 80% of the 31,365 acres of corn protected by the adult corn rootworm management program over five years would have received the commonly used 20 oz. of organophosphorous insecticide per acre, 25,092 acres would have been treated with 501,840 oz. of active ingredient. This is 31,365 lbs. of actual toxicant rather than the 1,467 lbs. of carbaryl that were applied to the Iowa managed area during the study, which is more than a 20-fold reduction in insecticide load in the environment. The northern corn rootworm that has a 2-year diapause was found throughout eastern Iowa. Thus the entire state is infested with them. The western corn rootworm that survives in rotated corn was found in eastern Iowa, and reached economic infestation levels in east central Iowa locations. At the Integrated Crop Management annual meeting and at regional Extension meetings growers were urged to begin monitoring programs. It was suggested that they could begin with 6 sticky traps in a soybean field, and if western corn rootworms were caught, increase the number of traps to 12 to monitor for economic populations. Aerial applications of insecticide to soybean fields where the grape colaspis was found were used to attempt to control them. Black cutworm attack in YieldGard plots after herbicide application was too variable to document that weed control would reduce the control of the cutworm after herbicide application. There was variability in the susceptibility of Croatian and Serbian commercial corn lines to corn rootworm attack. The data were returned to collaborators at the Maize Research Center in Serbia and University of J.J. Strossmayer in Croatia. It was intended that the results would be used in their local Extension meetings to allow growers the opportunity to select varieties that are less susceptible to corn rootworm injury. The commercial corn varieties that have been genetically engineered to be tolerant of rootworm attack performed very well in the evaluation trials. There have been growers' fields where these varieties did suffer substantial injury. Visits to these fields could not determine a reason for the injury.
Publications
- Sappington, T.W., K.R. Ostlie, C. DiFonzo, B.E. Hibbard, C.H. Krupke, P. Porter, S.R. Pueppke, E.J. Shields, J.J. Tollefson. (2010). Conducting public-sector research on commercialized transgenic seed. GM Crops 1(2): 1-4.
- Ivezic, M., Raspudic, E., Brmez, M., Majic, I., Brkic, I., Tollefson, J., Bohn, M., Hibbard, B.E., Simic, D. (2009). A review of resistance breeding options targeting western corn rootworm (Diabrotica virgifera virgifera LeConte). Agriculture and Forest Entomology 11: 307-311.
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Progress 01/01/08 to 12/31/08
Outputs
OUTPUTS: The corn rootworms (CRWs) traditionally have had a single generation per year and have been pests of corn planted continuously in the same fields. Recently variants of both the northern CRW and western CRW have developed rotation resistance (RR). The RR western corn rootworm was found in eastern IA in 2005, had spread in 2006 to 13 of 14 eastern IA counties scouted and had reached economic levels in 2 counties. During 2007, 18 locations in 14 counties were sampled in a north to south transect across eastern IA. To better map the distribution of the RR western CRW in 2008, 3 transects from the Mississippi River west to Interstate 35 were conducted: a northern one along highway 20, a central one along highway 30, and a southern route along highway 6. Two sites were monitored per county along the transects, with sites being identified by regional agronomists and cooperators, for a total of 38 sites. At each site Pherocon AM sticky traps were placed in soybean and adjacent corn fields following the University of Illinois protocol. Within each field, traps were placed in two lines of six and separated by 20m. Lines of traps were separated by at least 100m and located no closer than 50m from any field edge. Sticky traps were placed in corn and soybean fields starting in the last week in July and were changed weekly. In the last week of August, sticky traps in corn fields were removed and traps in soybean fields were reduced from 12 traps per field to 6 traps per field. A total of three weekly samples were collected from corn fields and five weekly samples from soybean fields. WCR and NCR per trap were counted to calculate the average number of WCR and NCR per trap per day at each site. The western CRW was discovered in Serbia in 1992. In an effort to help develop management strategies, eleven commercial Serbian corn hybrids were planted in fields infested with CRW. A complete randomized block design with paired rows (insecticide treated versus non-insecticide treated) was established at one location in central Iowa and evaluated for CRW injury and corn growth response to the injury. The corn tolerance responses to larval feeding measured were root size and regrowth following injury. Genetically-engineered CRW resistant commercial corn varieties and insecticides were compared in experiments at four locations in Iowa. At Ames, Johnson Farm; Crawfordsville, S.E. Research and Demonstration Farm; and Sutherland, N.W. Research and Demonstration Farm, studies were randomized complete block experiments. Multiple-row plots established with commercial farm equipment were used to match farmer practices. Performance was quantified as the degree of root protection, lodging resistance, and yield, among 27 commercially available products. Additionally, 12 experimental treatments were scored for root protection. Effect of insecticide in combination with transgenic technology was tested at Sutherland, N.W. Research and Demonstration Farm in a Monsanto-Bayer yield study. Treatments in this study were eight rows wide and 75 feet in length. The experimental design was a split plot. PARTICIPANTS: Tollefson, Jon and Gassmann, Aaron, Principal Investigators: Project development and research coordination personnel recruitment and supervision, data analysis and summarizing, and reporting results. Prasifka, Patricia, Post-Doctoral Fellow and Dunbar, Michael, Graduate Research Assistant: Developed, executed and reported research on the rotation resistant corn rootworms. Melissa Rynerson, Graduate Research Assistant: surveyed corn fields for naturally occurring pathogens of corn rootworm. Oleson, James and Weber, Pat, Research Specialists: Contracted research with plant protection industries. Designed and executed research protocols and conducted research on plant protectorates. Collected, summarized and reported data from the plant protection trials. Kadlicko, Stephanie, Graduate Research Assistant: Coordinated corn rootworm tolerance research with Serbian entomologist and corn breeder. Conducted the research, collected and analyzed the tolerance data and reported the results in her M.S. thesis. Baca, Franja, Entomologist and Stankovic, Goren, corn breeder. Collaborators: Research Scientists from the Maize Research Institute, Belgrade, Serbia. The collaborators chose and provided seed for the corn lines that the institute wanted screened for tolerance or resistance to the corn rootworms. TARGET AUDIENCES: Target audiences include the scientific research community, extension specialists, farmers, lawmakers, and the general public, as they are interested. Data from the experiments were disseminated in oral presentations at: 1) four presentations on corn rootworm management at Field Extension Education Lab field days, 2) Iowa Field Crop Agronomists in-service training, 3) two Crop Advantage Series meetings, and 4) weekly state-wide conference calls with Extension Agronomists. Electronic presentations were made in the Integrated Crop Management Newsletter and PowerPoint graphics provided to extension entomologists and field agronomists for use in their client meetings. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
Captures of rotation resistant (RR) western corn rootworms (CRWs) were low in eastern IA rotated corn; however, captures of RR northern CRWs were high. Based on these data, economic RR western CRW are confined to east central IA. In areas further west that were surveyed in 2008, management of RR western CRWs would not be recommended; however, monitoring with a reduced number of yellow sticky cards (6 instead of 12) was recommended. The lower-precision survey would help growers know when RR western CRWs enter their fields so that they can begin management. Because captures of RR northern CRWs were high in the areas surveyed and there is no reliable sampling method, growers have been urged to consider managing this pest in first-year corn using insecticides, genetically-engineered resistant varieties or extended rotations if they observe lodging of corn in their rotated cornfields. A systematic survey of the eastern half of IA revealed that rotation-resistant WCR is present in the northeast and east-central parts of the state. Conclusions about the southern transect are difficult to draw as the number of WCR was especially low. Extreme weather in spring of 2008 and later planting dates could have combined to considerably reduce overall rootworm populations this season. Three of the commercial Serbian hybrids appear to possess tolerance or resistance to western CRW injury. These varieties may be wise choices for Serbian farmers that cannot afford insecticides, choose not to use insecticidal treatments, or do not have access to genetically-engineered, CRW-resistant varieties. The CRW feeding pressure ranged from 0.00 (DKC61-69, YieldGard VT Triple) to 0.95 (Pioneer 33D13; which is a non-Bt isoline) in the Ames yield study. There were significant differences among treatments in node injury, product consistency and lodging. No differences were noted among yields. The corn rootworm feeding pressure at the Nashua yield trial was moderately heavy with a range of 1.80 to 2.87 nodes injured in the CHECKS. All treatments, with the exception of Poncho 1250 seed treatment, had significantly lower node-injury scores than the CHECKS. The hybrid DKC61-69 (YieldGard VT Triple) had only a 0.08 node-injury rating and was not significantly less than the treatments that added an insecticide on top of the YieldGard VT Triple. There was over a 100 bushel difference among the yields and significant difference among treatments. There were two hybrids tested in the Monsanto-Bayer study, Hybrid DKC 61-72 (isoline) and DKC 61-69 (YieldGard VT Triple). Both of these hybrids were either treated with Poncho 1250, treated with Aztec, or given no additional protection. Percent lodging was significantly higher for DKC 61-72 (Check) and DKC 61-72 treated with Poncho 1250 than for the other treatments. Yield was significantly higher for DKC 61-69 than DKC 61-72 regardless of soil insecticide treatment.
Publications
- Gassmann, A. J., Carriere, Y., and Tabashnik, B. E. 2009. Fitness costs of insect resistance to Bacillus thuringiensis. Annual Review of Entomology 54: 147-163.
- Kadlicko, S. 2008. Evaluation of Serbian commercial hybrid tolerance to feeding by larval western corn rootworm (Diabrotica virgifera virgifera LeConte) using the novel difference approach. M.S. Thesis, Iowa State Univ., Ames.
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Progress 01/01/07 to 12/31/07
Outputs
OUTPUTS: The corn rootworms (CRWs) traditionally have had a single generation per year and have been pests of corn planted continuously in the same fields. Recently variants of both the northern CRW and western CRW have developed rotation resistance (RR). Eighteen locations in east-central Iowa were sampled for RR western and northern corn rootworms durng 2007. Two monitoring methods, emergence cages in first-year corn and yellow sticky traps in soybeans, were used to survey for RR rootworms (12 traps per field). Five locations (1 in central Iowa and 4 in northeast Iowa), were studied for evidence of egg laying in soybeans by the northern CRW using a new scouting method, egg traps (18 traps per field). The western CRW was discovered in Serbia in 1992. In an effort to help develop management strategies, eleven commercial Serbian corn hybrids were planted in fields infested with CRW. A complete randomized block design with paired rows (insecticide treated versus non-insecticide
treated) was established at one location in central Iowa and evaluated for CRW injury and corn growth response to the injury. The corn tolerance responses to larval feeding measured were root size and regrowth following injury. During 2007, genetically-engineered CRW resistant commercial corn varieties and an insecticide were compared in experiments at four locations in Iowa. The studies were randomized complete block experiments. Multiple-row plots using commercial farm equipment were used to match farmer practices. The degree of root protection, lodging resistance, and yield provided by the three corn rootworm Cry protein technologies and a standard soil insecticide - Aztec 2.1G were measured and compared.
PARTICIPANTS: Tollefson, Jon, Principal Investigator: Project development and research coordinator. Personnel recruitment and supervision. Data analysis and summarizing and reporting results. Prasifka, Patricia, Post Doctoral Fellow: Developed, executed and reported research on the rotation resistant corn rootworms. Oleson, James, Research Specialist: Contracted research with plant protection industries. Designed and executed research protocals and conducted research on plant protectorants. Collected, summarized and reported data from the plant protectorant trials. Kadlicko, Stephanie, Research Associate: Coordinated corn rootworm tolerance research with Serbian entomologist. Conducted the research, collected and analyzed the tolerance data and will report the results. Kiley, Nicholas, Seasonal Employee: Assisted in the execution of the research projects. Shared in the attempt to diagnose rootworm egg laying in soybeans using the egg trap. Baca', Franja, Collaborator: Research
entomologist from the Maize Ressearch Institute, Belgrade, Serbia. Professor Baca' chose and provided seed for the corn lines that the institute wanted screened for tolerance or resistance to the corn rootworms.
TARGET AUDIENCES: Target audiences include the scientific research community, extension specialists, farmers, lawmakers, and the general public, as they are interested. Data from the experiments were disseminated in oral presentations at: 1) the annual meeting of the SE Iowa Agricultural Research Association, 2) Iowa Field Crop Agronomists in-service training, 3) a SE Iowa Agriculture Research Association field day, 4) the Benton County pest management tour, 5) the fall Integrated Crop Management Conference, 6) two Agricultural Chemical Dealer updates, 7) two Crop Advantage Series meetings and 8) weekly state-wide conference calls with extension agronomists. Written presentations were made as a poster presentation at the annual meeting of the Entomological Society of America, articles in the Integrated Crop Management Newsletter and PowerPoint graphics provided to extension entomologists for use in their client meetings.
Impacts
Captures of rotation resistant (RR) western corn rootworms (CRWs) were low in eastern IA rotated corn; however, captures of RR northern CRWs were high. Based on these data, economic RR western CRW are confined to east central IA. In areas further west that were surveyed in 2007, management of RR western CRWs would not be recommended; however, monitoring with a reduced number of yellow sticky cards (6 instead of 12) was recommended. The lower-precision survey would help growers know when RR western CRWs enter their fields so that they can begin management. Because captures of RR northern CRWs were high in the areas surveyed and there is no reliable sampling method, growers have been urged to consider managing this pest in first-year corn using insecticides, genetically-engineered resistant varieties or extended rotations if they observe lodging of corn in their rotated cornfields. Three of the commercial Serbian hybrids appear to possess tolerance or resistance to
western CRW injury. These varieties may be wise choices for Serbian farmers that cannot afford insecticides, choose not to use insecticidal treatments, or do not have access to genetically-engineered, CRW-resistant varieties. All three transgenic, commercial US varieties and the Aztec 2.1G treatment significantly reduced root injury and had significantly higher yields when compared to the untreated check. However, at the Nashua location Pioneer 34A20 (Herculex XTRA) and Monsanto DKC60-18 (YieldGard Plus) provided significantly better protection than Syngenta's N67-W2 (Agrisure CB/LL/RW) and Aztec 2.1G. Monsanto DKC60-18 provided consistently high yields at all locations.
Publications
- Tollefson, J.J., Prasifka, P.L., and Kaeb, B.C. 2007. The monster in Iowa corn fields. Integrated Crop Management Newsletter, Iowa State University IC-498 (1): 18-20
- Tollefson, J.J. and Rice, M.E. 2007. When should you be concerned about adult corn rootworm feeding on your corn? Integrated Crop Management Newsletter, Iowa State University IC-498 (20): 254
- Rice, M.E., Oleson, J.D., and Tollefson, J.J. 2007. Evaluation of Corn Rootworm Hybrids. Integrated Crop Management Newsletter, Iowa State University IC-498 (26): 286-7
- Prasifka, P.L., Tollefson, J.J. and Kiley, N. 2007. Rotation Resistant Rootworms. Proceedings of the 19th Annual Integrated Crop Management Conference, Iowa State University, Ames, IA
- Payne, J., Wintersteen, W., Robertson, A., Munkfold, G., Pecinovsky, K., Fawcett, J., Duffy, M., Kaeb, B., Al-Kaisi, M., Hanna, M., Pringnitz, B., Wisner, R., Abendroth, L., Elmore, R., Rouse, J., Tylka, G., Mallarino, A., Pope, R., Owens, M., Sawyer, J., Correll, D., Tollefson, J., Prasifka, P., Rice, M., Arrowsmith, K., and Halloum, D. 2007. Integrated Crop Management: Special Issue Corn Following Corn, February 12. Recipient of the American Society of Agronomy's 2007 Extension Education Materials Contest, Certificate of Excellence.
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Progress 01/01/06 to 12/31/06
Outputs
Products for corn rootworm larval control were tested at five locations throughout Iowa. Products included granular and liquid insecticides, seed treatments, and plant-incorporated protectants (transgenic seedcorn that contains a gene from the naturally occurring soil bacterium Bacillus thuringiensis (Bt)). Both developmental and commercially available products were tested. Data collected included stand counts, root-injury scores, percentage lodged plants, and yields. At two other locations, similar products were tested for control of wireworms and seedcorn maggots. At all locations transgenic seedcorn provided good protection to roots and, in some cases, significantly increased yield. Granular and liquid insecticide treatments on the whole also performed well; however, seed treatments often failed to provide significant root protection. Due to low infestations, no significant differences were seen among wireworm treatments or in the seedcorn maggot test. Nine
locations were sampled for northern CRW egg laying in soybeans and 20 locations were sampled for rotation-resistant western and extended-diapause northern corn rootworm. In four northeastern fields, there was some evidence that northern corn rootworms were laying eggs in soybeans at very low levels. These results may indicate a new threat to first-year corn. Rotation-resistant western corn rootworms were present in 19 of the 20 locations in eastern Iowa and were found in economically significant numbers in Scott and Clinton counties (densities that warrant control if corn is planted in those fields next year). Extended diapause northern corn rootworms have been confirmed to be present throughout the state.
Impacts
Crop rotation can no longer be relied upon to avoid corn rootworm infestations because extended-diapause northern corn rootworm is distributed throughout the state, rotation-resistant western corn rootworm is present throughout eastern Iowa (at economic levels in east-central Iowa), and there is some evidence that northern corn rootworms may be laying eggs in soybean (potentially posing a risk to first year corn). Growers are being encouraged to sample their soybean fields for the presence of rootworm adults to help predict whether some form of management is warranted if that field is rotated to corn. Transgenic Bt seedcorn continues to be a valuable and effective tool for rootworm management, showing superior root protection and yield especially under moisture stress.
Publications
- Park, YL and J.J. Tollefson. 2006. Development and economic evaluation of spatial sampling plans for corn rootworm Diabrotica spp. (Coleoptera: Chrysomelidae) adults. J. Appl. Entomol. 130: 337-342.
- Park, YL and J.J. Tollefson. 2006. Spatio-temporal dynamics of corn rootworm, Diabrotica spp., adults and their spatial association with environment. Entomol. Exp. et Appl. 120: 105-112.
- Park, YL and J.J. Tollefson. 2006. Spatial distributions of corn rootworm (Coleoptera: Chrysomelidae) eggs and larvae: Implications for sampling. J. Kan. Entomol. Soc. 79: 129-135.
- Boetel, M.A., B.W. Fuller, L.D. Chandler, J.J. Tollefson, B.M. McManus, N.D. Kadakia, P.D. Evenson, and T.P. Mishra. 2005. Nontarget arthropod abundance in areawide-managed corn habitats treated with semiochemical-based bait insecticide for corn rootworm (Coleoptera: Chrysomelidae) control. J. Econ. Entomol. 98: 1957-1968.
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Progress 01/01/05 to 12/31/05
Outputs
In field research to evaluate the durability of Herculex(TM) I genetically modified fieldcorn against black cutworm attack, there was a significantly greater amount of cutting in the isoline than Herculex(TM) I, but no significant difference in Herculex(TM) I treatments with and without weed removal. Black cutworm larvae were fed Herculex(TM) I or isoline corn and then exposed to Agrotis ipsilon multicapsid nucleopolyhedrovirus. Of the exposed larvae, those fed the Herculex(TM) I diet had significantly higher rates of virus infection than those fed the isoline diet. Insecticidal seed treatments protected seed corn from grape colaspis larval feeding. The chemically protected seeds consistently produced taller seed corn. Insecticidal treatments to soybeans reduced the adult population of adult grape colaspis beetles and the population reduction carries over to the larvae of the next generation. Farmers were enlisted to conduct a qualitative survey to determine how
abundant the rotation-resistant western corn rootworm (WCR) and extended-diapause northern corn rootworms (NCR) were in eastern Iowa. Rootworm injury to rotated corn continues to spread through out Iowa; both because of the increased range of the extended-diapause NCR and the appearance of the rotation resistant WCR. The abundance of the rotation-resistant WCR is low, however, and not causing economic injury. Under drought conditions and heavy corn rootworm infestations in southeast Iowa, YieldGard Plus corn provided a 70 bu/a yield advantage over the best insecticide treatment, 171 and 101 bu/a, respectively. Herculex RW corn provided excellent root protection at this same location (no yield data taken).
Impacts
Genetically modified Herculex(TM) I fieldcorn deterred black cutworm larval injury with or without an alternative host, showing that it would not suffer early season damage when growers use post-emergence herbicides. If grape colaspis adults are present in soybeans, the beans can be treated to control the adults or insecticidal seed treatments can be applied to seedcorn to reduce losses in seed-production fields. Crop rotation can no longer be relied upon to avoid corn rootworm infestations because the extended-diapause northern corn rootworm is distributed through out the state and the rotation-resistant western corn rootworm is now present in eastern Iowa. Bt protein protection from rootworms in genetically-engineered corn is extremely important if the crop is under moisture stress, returning a 70 bu/a yield advantage over the best insecticide treatment.
Publications
- Wilson, T.A., M.E. Rice, J.J. Tollefson, and C.D. Pilcher. 2005. Transgenic corn for control of the European corn borer and corn rootworms: a survey of Midwestern farmers' practices and perceptions. J. Econ. Entomol. 98:237-247.
- Oleson, J.D., Y.L. Park, T.M. Nowatzki, and J.J. Tollefson. 2005. Node-injury scale to evaluate root injury by corn rootworms (Coleoptera: Chrysomelidae). J. Econ. Entomol. 98:1-8.
- Park, Y.L., and J. J. Tollefson. 2005. Characterization of the spatial dispersion of corn root injury by corn rootworms (Coleoptera: Chrysomelidae). Journal of Economic Entomology 98:378-383.
- Park, Y.L., and J. J. Tollefson. 2005. Spatial prediction of corn rootworm (Coleoptera: Chrysomelidae) adult emergence. Journal of Economic Entomology 98:121-128.
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Progress 01/01/04 to 12/31/04
Outputs
The grape colaspis has been a sporatic pest of field crops in Iowa. The last several years it has become a frequent pest in seed corn production. Because of the high value of the seed production, seed producers have asked for management alternatives. Insecticides were applied to soybean fields where seed corn would be planted the following year to prevent egg laying. The insecticides were applied too late to be effective and emergence monitoring confirmed that applications must be made earlier. Insecticidal seed treatments were shown to significantly reduce grape colaspis larval injury in seed corn. The response of black cutworms to genetically-engineered, Bt corn (Herculex I) was examined to determine if it would maintain resistance when alternate hosts were removed. There was too much variability in the field experiments and the research is being repeated in the greenhouse to control the sources of variation. Experimental and labeled soil insecticides were tested
throughout Iowa for efficacy against corn rootworm, wireworms, white grubs and seedcorn maggots. The results are released in annual, public reports. Genetically engineered corn resistant to corn rootworms from Monsanto, Pioneer and Syngenta were evaluated each at a single location.
Impacts
Seed corn is a high-value crop. If there is a chance of a grape colaspis infestation, a grower may loose their contract. Insecticidal seed treatments were shown to reduce grape colaspis injury to inbred corn planted for seed production.
Publications
- No publications reported this period
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