Progress 09/01/09 to 08/31/12
Outputs
OUTPUTS: Western corn rootworm (WCR) is the most significant U.S. corn pest. Rootworm-resistant Bt-corn hybrids offer WCR control equal to insecticide with simplified planting operations and reduced chemical exposure. Use of Bt-hybrids requires establishment of non-Bt corn refuges to nurture modest populations of susceptible WCR adults intended to disperse and mate with potentially-resistant WCR adults that develop in Bt corn. Matings between WCR from refuge and transgenic corn will delay development of Bt resistance. An abundance of susceptible beetles entering transgenic corn reduces the likelihood that any two potentially-resistant WCR will mate; this slows the rate of resistance development. This study's goal was to measure the abundance and behavior of WCR beetles as they move and mate in different configurations of refuge and transgenic corn. From 2010 to 2012, we planted three replicates of four refuge treatments (i.e. 20 and 5 percent structured block refuges, a 5 percent seed blend, and a 0 percent refuge control). We measured/analyzed the emergence, abundance, mating activity, and movement of WCR adults in study plots; similar studies to measure abundance and mating also occurred in large on-farm fields belonging to cooperators in 2010-2011. Results were similar across years. Analyses indicate that: 1) WCR abundance was greatest in refuge areas of structured block refuge fields, 2) male and female adult emergence from refuge was 3.9 times that from transgenic in 2010; refuge emergence was 1.9 times in 2011 and 2012, 3) 50 percent cumulative emergence of refuge males and females preceded that of adults from transgenic every year, 4) WCR adults in refuge corn rows are larger than those in transgenic rows for 2010 and 2011 (2012 data not yet analyzed), 5) refuge WCR (2010 and 2011) moved into transgenic corn at ca. 12.3 to 13.1 m/day; a concurrent mark release recapture study in 2012 measured cornfield movement as 14.4 m/day), 6) the greatest proportion of (intrafield) moving refuge males was found in transgenic corn during the vegetative corn phenology (0.306; 2010 plus 2011); it was 0.039 during pollination and 0.011 after pollination; proportions of female movers are similar in magnitude and timing, interfield movement accounted for 0.80 and 3.5 percent of male and female captures, 7) mating activity was greatest in structured refuges and mating activity was delayed in transgenic portions of structured refuges and the mating females were older in all three years, 8) a total of 617 mating pairs were analyzed in 2010 and 2011; among 213 pairs in transgenic corn only 2 pairs (0.94 percent) contained a refuge male (2012 analyses 223 mating pairs is incomplete), 9) the seed blend produced evenly distributed WCR abundance and mating patterns throughout the growing season in all years. These data suggest that a seed blend is superior to block refuges for moving and mixing mate-seeking WCR. Intrafield movement in block refuge fields is poor compared to expectations from literature. 2012 analyses are continuing. Observation of actual behavior, not our assumptions, should guide refuge design. PARTICIPANTS: Individual: Principal investigator and Project director: Dr. Joseph Spencer. Supervised the overall project, established insect sampling procedures at on-farm and research plot locations, supervised and participated in daily data collection, sample storage, data management, field clean-up, and analysis for all objectives. Dr. Spencer supervised 1 graduate research assistant (funded on this project) and 12-student hourly assistants and interns who worked at least part time on the project. Individual: Graduate Student: Sarah A. Hughson. M.S. Graduate research assistant in the University of Illinois Department of Entomology whose program is funded by this project. Ms. Hughson participated in insect sampling at on-farm and research plot locations, participated in daily data collection, sample storage, data management, field clean-up, and analysis for all objectives. She was completely or partially supported on this project during 2010-2012 (She also assisted with supervision of 12-undergraduate (UG) student hourly assistants and interns in 2010, 8-UG student hourly assistants and interns in 2011, and 6-UG student hourly assistants in 2012). Individuals: Hourly student workers 2010-2012 (summer and/or school year workers): 2010 Carl Carman, Theresa Emmerling, Ashley Higgins, Charles Keegan, Merilin Barahona, Johnny McQuillan, Kyle Rockershousen, Andrew Nelson, Matthew Olin, Andrew Kumler, and Travis Wilkinson; 2011 Theresa Emmerling, Ashley Higgins, Merilin Barahona, Patrick Olin, Kirk Buetke, Jungkoo Kang, Sam Moses, Jacob McQuaid, and Eliana Rosales; and 2012 Dario Aguilar, Ted Brown, Sarah Buhmann, Miles Henderson, Jacob McQuaid and Adam Olin. All were responsible for assisting the PI/PD with all work to establish field plots, mark sample locations, collect and sort/count weekly samples, label and archive samples, and prepare samples for later analyses. Partner Organizations: Cooperating Producers: Mr. Rick Nelson, Paxton, IL (Ford County), provided a 39 acre field on his farm. Mr. Dale Stierwalt, Tolono, IL (Champaign County), provided a 50 acre field on his farm in 2010. In 2011, Cooperating Champaign County Producers were Mr. Greg Frerichs (Rantoul, IL), Mr. Dale Franzen (Rantoul, IL), Mr. Paul Compton (Sidney, IL), and Mr. Tom Cain (Philo, IL). They provided cornfields where we conducted abundance and monitoring studies that paralleled our research farm experiments. No on-farm work was conducted in 2012. TARGET AUDIENCES: The target audience for this project are those who will benefit from our findings, they are entomologists, U.S Corn Belt producers, crop consultants, and agricultural/Extension professionals along with scientists with biotechnology companies (Pioneer Hi-Bred International donated seed corn for this project), EPA and regulatory bodies responsible for insect resistance management policy. Findings of these experiments were the subject of presentations during the 2010-2012 University of Illinois Agronomy Day presentations during August of each year (a meeting is attended by hundreds of producers from Illinois and nearby regions of adjacent states). Data from this study have been presented at a European meeting in Frieburg, Germany, where primarily European scientists who must manage WCR as an invasive pest spreading outward from central Europe are interested in the movement aspects of this work. In 2012, results from the entire project were summarized in written and or oral presentations to representatives of Monsanto Company, Pioneer Hi-Bred International, and Syngenta. An extensive review of these data in relation to Bt resistance was part of a presentation to agricultural business professionals at the University of Illinois AG Masters Conference. PROJECT MODIFICATIONS: A no-cost extension of the ending date was requested on 12 July 2011 and granted. The project concluded on 31 August 2012. The extension was necessary because the ending date of the grant falls at a time when there is still significant field and laboratory work to be completed on the project (e.g. 2011 insect collections and the complete analyses of insects collected during the 2011 summer of fieldwork were still in progress on the completion date, the post-season analyses of 2011 findings continued well into 2012 necessitating employment of assistants and purchase of supplies. A more limited analyses of 2012 data will be completed by early in 2013. Participant Sarah Hughson will write an MS thesis with these data and develop 2-3 publications in the coming year. Papers are anticipated to be published by 2013 and 2014. On 27 March 2012 a re-budget was requested. It was needed because the subject pest population was low in 2010 and 2011; meaning fewer than expected insects were available for collection in those project years (thus there were reduced expenses for testing materials and fewer wages spent on testing). A shifting of surplus was used to yield a third year of data (in the no-cost extension year) by redistributing unexpended materials and supplies funds principally to wages/fringes, contractual and travel lines.
Impacts
Measurement of actual WCR movement and mating in refuges under field conditions is a practical way to understand if refuges perform as expected. Collection of data that resulted in outcomes that corrected erroneous assumptions about pest biology are valuable because they improve insect resistance management models of refuge design. The observations that 1) refuge male movement into transgenic corn from block refuges is most likely during the vegetative period of corn phenology, 2) that mating activity is concentrated in and around block refuges, and 3) that mating females just outside of refuge corn are older than mating females in refuge corn (this may indicate that while males are abundant in refuge, the proportion of males that are still reproductively competent may be quite low; many refuge females may wander out of refuges while they wait to be discovered by a mate-seeking male) illustrate some departures from assumptions that were accepted in current models. Limitations on male reproductive lifespan were not measured as part of this study; however, patterns of mating activity suggest that WCR male mating capabilities are less than what has been assumed in many models. During presentations in various venues, project findings have consistently been used to promote seed blends as superior refuge designs for assuring well-mixed WCR populations. These data have been embraced by industry; they have been used for or influenced new Insect Resistance Management models. During many presentations to growers, suggesting WCR beetle behavior was out of compliance with our expectations was found to be an effective shift of perspective, and one that is more favorably received than assertions that growers have failed to comply with refuge . These changes in knowledge about WCR 1) movement and 2) mating behavior/patterns were incorporated into a published model (Pan et al. 2011) and a Entomologia Experimentalis et Applicata publication in press (Spencer et al.) about expectations for WCR mating in Bt corn. Discussion of yearly finding occurred in 2010-12 University of Illinois Agronomy Day presentation proceedings (1,2,4). Since these data and a model using project male WCR abundance and movement data were submitted to an EPA-SAP docket, these data may affect policy knowledge and decision-making rules about refuge configuration for transgenic pyramided hybrids included in seed blends. The 2010-12 data were shared with EPA-OPP, and portions of these data were shared with collaborators at Pioneer Hi-Bred International. Publication of the first evidence of field-evolved WCR resistance to a cry protein expressed in a Bt-corn hybrid (Gassmann et al. 2011, PLoS One) highlights the urgency of understanding if the refuge strategy works for WCR and what might be done to improve efficacy and grower compliance. Since commodity economics favor more corn-on-corn, demonstrating why and how one refuge configuration is superior to others may at least raise awareness that refuge matters.
Publications
- Spencer, J.L. and Hughson, S.A. 2010. The rootworms opinion of reduced refuge. The University of Illinois 2010 Agronomy Day Program and Abstract Book. Crop Sciences Research and Education Center. Urbana, Illinois. August 19, 2010.
- Spencer, J.L. and Hughson, S.A. 2011. Rootworms and refuge: Is one strategy better The University of Illinois 2011 Agronomy Day Program and Abstract Book. Crop Sciences Research and Education Center. Urbana, Illinois. August 18, 2011.
- Onstad, D.W., Mitchell, P.D., Hurley, T.M., Lundgren, J.G., Porter, R.P., Krupke, C.H., Spencer, J.L., DiFonzo, C.D., Baute, T.S., Hellmich, R.L., Buschman, L., Hutchison, W.D. and Tooker, J.F. 2011. Seeds of change: Corn seed mixtures for resistance management and IPM. Journal of Economic Entomology, 104(2):343-352.
- Spencer, J.L. and Hughson, S.A. 2012. Reality vs. assumptions about rootworm behavior in refuge and Bt corn. The University of Illinois 2012 Agronomy Day Program and Abstract Book. Crop Sciences Research and Education Center. Urbana, Illinois. August 16, 2011.
- Spencer, J.L., Onstad, D., Krupke, C., Hughson, S., Pan, Z., Stanley, B. and Flexner, L. 2012. Isolated females and limited males: Evolution of insect resistance in structured landscapes. Entomologia Experimentalis et Applicata. (In Press).
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Progress 09/01/10 to 08/31/11
Outputs
OUTPUTS: Western corn rootworm (WCR) is a significant pest of U.S. corn. Rootworm-resistant Bt-corn hybrids offer WCR control equal to insecticide with simplified planting operations and reduced chemical exposure. Use of Bt-hybrids require establishment of non-Bt corn refuges (equal to 5-20 percent of Bt-planted area) to nurture modest populations of susceptible WCR adults intended to disperse and mate with more sparsely-distributed, potentially-resistant WCR adults that develop in Bt corn. Mating between WCR from refuge and transgenic corn will delay development of Bt resistance. An abundance of susceptible beetles entering transgenic corn reduces the likelihood that any two potentially-resistant WCR will mate; this slows the rate of resistance development. Our goal is to measure the behaviors of WCR beetles as they move and mate in different configurations of refuge and transgenic corn. In 2010 and 2011, we planted 3 replicates of 4 refuge treatments (i.e. 20 and 5 percent structured block refuges, a 5 percent seed blend, and a 0 percent refuge control). We measured/analyzed the emergence, abundance, mating activity, and movement of WCR adults in study plots; similar studies to measure abundance and mating also occurred in large on-farm fields belonging to cooperators. The results from both years are very similar. Analyses from both years indicate that: 1) WCR abundance was greatest in refuge areas of structured block refuge fields, 2) emergence data showed that male and female adult production in transenic corn was ca. 10 percent of that in refuge corn rows; 50 percent cumulative emergence of refuge males and females preceded that of adults from transgenic, 3) WCR adults in refuge corn rows are larger than those in transgenic rows, 4) refuge WCR move into transgenic corn at ca. 12.3 to 13.1 m/day), 5) the greatest proportion of (intrafield) moving refuge males was found in transgenic corn during the vegetative corn phenology (0.306); it was 0.039 during pollination and 0.011 after pollination; proportions of female movers are similar, interfield movement accounted for 0.80 and 3.5 percent of male and female captures, 6) mating activity was greatest in structured refuges, 7) mating activity was delayed in transgenic portions of structured refuges and the mating females were older, 8) A total of 617 mating pairs were analyzed in 2010 and 2011; among 213 pairs in transgenic corn only 2 pairs (0.94 percent) contained a refuge male, 9) a 5 percent seed blend produced evenly distributed WCR abundance and mating patterns through out the growing season. These data suggest that a seed blend is superior to block refuges for moving and mixing mate-seeking WCR. Analyses of 2011 WCR continue. It is important to pay attention to what insects are actually doing because their behavior, not our assumptions about their behavior determine how well refuge designs function. 2011 results were shared at one field day, an invited seminar, a European corn pest conference, a regional working group conference, and a symposium at the Entomological Society of America national meeting. Results were also used in a resistance model focused on seed blends for managing WCR. PARTICIPANTS: Individual: Principal Investigator and Project Director: Dr. Joseph Spencer. Supervised the overall project, established insect sampling procedures at on-farm and research plot locations, supervised and participated in daily data collection, sample storage, data management, field clean-up, and analysis for all objectives. Dr. Spencer supervised 1 graduate research assistant (funded on this project) and 12-student hourly assistants and interns who worked at least part time on the project. Individual: Graduate Student: Sarah A. Hughson. M.S. Graduate research assistant in the University of Illinois Department of Entomology whose program is funded by this project. Ms. Hughson participated in insect sampling at on-farm and research plot locations, participated in daily data collection, sample storage, data management, field clean-up, and analysis for all objectives. She was completely or partially supported on this project during 2010-2011 (she also assisted with supervision of 6-student hourly assistants and interns). Individuals: Hourly student workers (8 summer and/or school year workers): Theresa Emmerling, Ashley Higgins, Merilin Barahona, Patrick Olin, Kirk Buetke, Jungkoo Kang, Sam Moses, Jacob McQuaid, and Eliana Rosales were responsible for assisting the PI/PD with all work to establish field plots, mark sample locations, collect and sort/count weekly samples, label and archive samples, and prepare samples for later analyses and conduct insect dissections. Partner Organizations: Cooperating Champaign County Producers: Mr. Greg Frerichs (Rantoul, IL), Mr. Dale Franzen (Rantoul, IL), Mr. Paul Compton (Sidney, IL), and Mr. Tom Cain (Philo, IL) provided cornfields where we conducted abundance and monitoring studies that paralleled our research farm experiments. TARGET AUDIENCES: The target audience for this project who will benefit from our findings are entomologists, U.S Corn Belt producers, crop consultants, and agricultural/Extension professionals along with scientists with biotechnology companies (Pioneer Hi-Bred International donates seedcorn for this project) as well as the EPA and regulatory bodies responsible for insect resistance management policy. Findings of these experiments were the subject of a presentation during the 2011 University of Illinois Agronomy Day presentations on August 18, 2011 (a meeting attended by hundreds of producers from Illinois and nearby regions of adjacent states). Two manuscripts in preparation based on data from these studies will reach the U.S. and international audiences (primarily European scientists who must manage WCR as an invasive pest spreading outward from central Europe). PROJECT MODIFICATIONS: A no-cost extension of the ending date was requested on 12 July 2011 and granted. The project will conclude on 31 August 2012. The extension was necessary because the ending date of the grant falls at a time when there is still significant field and laboratory work to be completed on the project (e.g. 2011 insect collections and the complete analyses of insects collected during the 2011 summer of fieldwork would (and are) still be in progress on the completion date, the post-season analyses of findings will continue well-beyond that date necessitating employment of assistants and purchase of supplies).
Impacts
An intention of this work is to go beyond the assumptions and measure what WCR adults actually do under field conditions; the best way to test how well refuges perform is to observe pests using them. Measuring outcomes that correct erroneous assumptions about pest biology are valuable to improve models of insect resistance and designs for refuge deployment in transgenic crops. The observations that WCR male movement from refuge to transgenic areas of fields is most likely during the vegetative period of corn phenology, that mating is concentrated in and around refuge, and that mating females outside of refuge are older than mating females in transgenic corn (i.e. males are perhaps so scarce that females wait longer to mate, leaving more time for a potentially-resistant male to locate a given female) illustrates some dramatic departures from assumptions that are accepted in current models. These changes in knowledge have been incorporated into a larger model of WCR resistance for seed blend/mixtures of transgenic corn submitted for publication. Because the model incorporating the measurements of male WCR abundance and movement patterns was submitted to the docket of an EPA Science Advisory Panel, there is a potential for these data to affect policy knowledge and decision-making rules about refuge configuration for transgenic pyramided hybrids included in seed blends. The 2010 and 2011 data were shared with EPA-OPP, and portions of these data were shared with collaborators at Pioneer Hi-Bred International. These data have been used by EPA in review of product registrations for blended Bt-corn pyramids. Publication of the first evidence of field-evolved WCR resistance to a cry protein expressed in a Bt-corn hybrid highlights the urgency of understanding if the refuge strategy is working for WCR and what might be done to improve efficacy and grower compliance.
Publications
- Spencer, J.L. and Hughson, S.A. 2011. Rootworms and refuge: Is one strategy better The University of Illinois 2011 Agronomy Day Program and Abstract Book. Crop Sciences Research and Education Center. Urbana, Illinois. August 18, 2011.
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Progress 09/01/09 to 08/31/10
Outputs
OUTPUTS: Western corn rootworm (WCR) is a significant pest of U.S. corn. Rootworm-resistant Bt-corn hybrids offer WCR control equal to insecticide with simplified planting operations and reduced chemical exposure. Use of Bt-hybrids require establishment of non-Bt corn refuges (equal to 5-20 percent of Bt-planted area) to nurture modest populations of susceptible WCR adults intended to disperse and mate with more sparsely-distributed, potentially-resistant WCR adults that develop in Bt corn. Mating between WCR from refuge and transgenic corn will delay development of Bt resistance. An abundance of susceptible beetles entering transgenic corn reduces the likelihood that any two potentially-resistant WCR will mate; this slows the rate of resistance development. This study's goal is to measure the behaviors of WCR beetles as they move and mate in different configurations of refuge and transgenic corn. In 2010, we planted 3 replicates of 4 refuge treatments (i.e. 20 and 5 percent structured block refuges, a 5 percent seed blend, and a 0 percent refuge control). During conduction of this study, we measured/analyzed the emergence, abundance, mating activity, and movement of WCR adults in study plots. There were similar studies to measure abundance and mating in large on-farm fields belonging to cooperators. Ongoing analyses indicate that: 1) WCR abundance was greatest in refuge areas of structured block refuge fields, 2) refuge beetles move into transgenic corn slowly (max. rates were ca. 12.3 to 13.1 m/day), 3) the greatest proportion of moving refuge males was found in transgenic corn during the vegetative period of corn phenology (0.295); it fell to 0.033 during pollination and 0.008 after pollination, 5) WCR mating activity was greatest in refuge areas of structured refuge plots where ca. 80 percent of mating females were teneral (i.e. newly emerged), 6) mating activity was delayed in transgenic portions of structured refuges where more than half of mating females were non-teneral at mating), and 7) a 5 percent seed blend produced evenly distributed WCR abundance and mating patterns through out the growing season. These data suggest that a seed blend may be superior to block refuges for moving and mixing mate-seeking WCR. Emergence data showed that male and female adult production in transenic corn was 10.0 and 11.7 percent of that in refuge corn rows. Physical measurement of WCR indicates that males in refuge corn rows are larger than those from transgenic rows. The presence of WCR males bearing markers indicative of plot entry from another plot (i.e. Cry1Ab-positive males in 0 percent refuge plots) suggests that as many as 6.5 percent of males in a plot may have participated in interfield movement. Analyses of mating pairs and female WCR are ongoing. These data suggest that a seed blend may be superior to block refuges for moving and mixing mate-seeking WCR. Events at which some of these 2010 results were shared included two field days, a departmental seminar, and a regional working group conference. These results were also used in products: a resistance model leading to collaboration on a paper focused on seed blends for managing WCR. PARTICIPANTS: Individual: Principal Investigator and Project Director: Dr. Joseph Spencer. Supervised the overall project, established insect sampling procedures at on-farm and research plot locations, supervised and participated in daily data collection, sample storage, data management, field clean-up, and analysis for all objectives. Dr. Spencer supervised 1 graduate research assistant (funded on this project) and 12-student hourly assistants and interns who worked at least part time on the project. Graduate Student: Sarah A. Hughson. M.S. Graduate research assistant in the University of Illinois Department of Entomology whose program is funded by this project. Ms. Hughson participated in insect sampling at on-farm and research plot locations, participated in daily data collection, sample storage, data management, field clean-up, and analysis for all objectives. She also assisted with supervision of 12-student hourly assistants and interns. Student Hourly Workers: Hourly student workers (11 summer and/or school year workers): Carl Carman, Theresa Emmerling, Ashley Higgins, Charles Keegan, Merilin Barahona, Johnny McQuillan, Kyle Rockershousen, Andrew Nelson, Matthew Olin, Andrew Kumler, and Travis Wilkinson, were responsible for assisting the PI/PD with all work to establish field plots, mark sample locations, collect and sort/count weekly samples, label and archive samples, and prepare samples for later analyses. Partner Organizations: Cooperating Producers: Mr. Rick Nelson, Paxton, IL (Ford County); provided a 39 acre field on his farm. Mr. Dale Stierwalt, Tolono, IL (Champaign County); provided a 50 acre field on his farm. TARGET AUDIENCES: The target audience for this project who will benefit from our findings are Entomologists, U.S. Corn Belt producers, crop consultants, and agricultural/Extension professionals along with EPA and regulatory bodies responsible for insect resistance management policy. Findings of these experiments were mentioned during a presentation during the 2010 University of Illinois Agronomy Day presentations on August 19, 2010. This meeting is attended by hundreds of producers from Illinois and nearby regions of adjacent states. Prior to Agronomy day, the findings were highlighted during a 30 minute interview with Todd Gleason on Illinois Public Media - The Farming World that preceded the University of Illinois 2010 Agronomy Day on August 18, 2010. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
An intention of this work is to go beyond the assumptions and measure what rootworms actually do under field conditions; what better way to test how well refuges perform than to observe pests using them Measuring outcomes that correct erroneous assumptions about pest biology are valuable to improve models of insect resistance and designs for refuge deployment in transgenic crops. The observations that WCR male movement from refuge to transgenic areas of fields is most likely during the vegetative period of corn phenology, mating is concentrated in and around refuge, and that mating females outside of refuge are older than mating females in transgenic corn (i.e. males are scarce so females wait longer to mate, leaving more time for a potentially-resistant male to locate a given female) illustrates some dramatic departures from assumptions that are generally given credence in current models. These changes in knowledge have been incorporated into a larger model of WCR resistance for seed blend/mixtures of transgenic corn submitted for publication. Because the model incorporating the measurements of male WCR abundance and movement patterns has also been submitted to the docket of an EPA Science Advisory Panel, there is a potential for these data to affect policy knowledge and decision-making rules about refuge configuration for transgenic pyramided hybrids included in seed blends. Preliminary results of this study were also featured during a 30-minute interview with Todd Gleason on Illinois Public Media (The Farming World) that preceded the University of Illinois' 2010 Agronomy Day on August 18, 2010.
Publications
- Spencer, J.L. and Hughson, S.A. 2010. The rootworms opinion of reduced refuge. The University of Illinois 2010 Agronomy Day Program and Abstract Book: Crop Sciences Research and Education Center. Urbana, Illinois. August 19, 2010.
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