Location: Plant Genetics ResearchTitle: Comparative susceptibility of western corn rootworm (Coleoptera: Chrysomelidae) neonates to selected insecticides and Bt proteins in the presence and absence of feeding stimulants
|BERNKALU, ELISA - Colorado State University|
|BJOSTAD, LOUIS - Colorado State University|
Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/7/2018
Publication Date: 1/22/2019
Publication URL: http://handle.nal.usda.gov/10113/6471148
Citation: Pereira, A.E., Coudron, T.A., Shelby, K., French, B.W., Bernkalu, E.J., Bjostad, L.B., Hibbard, B.E. 2019. Comparative susceptibility of western corn rootworm (Coleoptera: Chrysomelidae) neonates to selected insecticides and Bt proteins in the presence and absence of feeding stimulants. Journal of Economic Entomology. 112(2):842-851. https://doi.org/10.1093/jee/toy415.
Interpretive Summary: Corn growers from the U.S. Corn Belt have faced problems with corn rootworms for a long time because of the evolution of resistance this corn pest to the control techniques. The search for new control or new application methods and new toxins to help control corn rootworm is an urgent need. The research for new pesticide molecules is costly and labor intensive, and can take over a decade to reach commercial status for a single pesticide. In order to evaluate current pesticides used for corn rootworm control, we tested several synthetic insecticides mixed with previously identified feeding stimulants found in corn root to increase susceptibility of the corn pest. The addition of the feeding stimulants did not increase significantly the susceptibility of the rootworm to the insecticides except one, a neonicotinoid, which is the newest insecticide class among those tested and that is currently used in corn seed treatments. Although the feeding stimulants only increased the effectiveness of one of the insecticides tested, this information can be used to target this particular insecticide more effectively.
Technical Abstract: The susceptibility of western corn rootworm (WCR), Diabrotica virgifera virgifera, larvae to nine insecticides from five different classes and to Bacillus thuringiensis (Bt) proteins eCry3.1Ab and mCry3A in the presence or absence of feeding stimulants, was estimated in filter paper and diet toxicity assays, respectively. The use of synthetic feeding stimulants (FS) to increase efficacy of insecticides and Bt proteins was evaluated by using glucose, sucrose, and fructose plus linoleic acid at a ratio of 30:4:4:0.3 mg/ml. Thiamethoxam diluted in solutions with FS was the only insecticide with significant increase in efficacy when compared to water (> 60-fold). In other insecticide classes, differences in susceptibility when diluted in FS solutions were no greater than 5-fold when compared to the insecticides diluted in water. The presence of corn root juice diminished toxicity of some of the insecticides, except for thiamethoxam, even though larval fresh weight was higher when fed on root juice compared to FS or water. The use of FS in diet toxicity assays did not enhance susceptibility of WCR neonates to the proteins eCry3.1Ab nor mCry3A. These results are discussed in terms of applicability of FS as larval attractant to improve susceptibility of WCR larvae to pesticides in general.