Susceptibility of northern corn rootworm (Diabrotica barberi) populations to Cry3Bb1 and Gpp34/Tpp35Ab1 proteins in seedling and diet overlay toxicity assays

Authors: Pereira, Adriano; HUYNH, MAN - University Of Missouri; Paddock, Kyle; GEISERT, RYAN - University Of Missouri; CALLES TORREZ, VERONICA - North Dakota State University; KNODEL, JANET - North Dakota State University; MOELLENBECK, DANIEL - Dm Crop Research Group, Inc; REINDERS, JORDAN - University Of Nebraska; MEINKE, LANCE - University Of Nebraska; Schneider, Sharon; Coudron, Thomas; Shelby, Kent; Hibbard, Bruce

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/10/2023
Publication Date: 2/12/2024
Citation: Pereira, A.E., Huynh, M.P., Paddock, K.J., Geisert, R.W., Calles Torrez, V., Knodel, J.J., Moellenbeck, D.J., Reinders, J.D., Meinke, L.J., Schneider, S.K., Coudron, T.A., Shelby, K., Hibbard, B.E. 2024. Susceptibility of northern corn rootworm (Diabrotica barberi) populations to Cry3Bb1 and Gpp34/Tpp35Ab1 proteins in seedling and diet overlay toxicity assays. Journal of Economic Entomology. 117(1):178-186. https://doi.org/10.1093/jee/toad221.
DOI: https://doi.org/10.1093/jee/toad221

Interpretive Summary: The northern corn rootworm (NCR) is a major pest of maize in the United States Corn Belt. Corn expressing Bacillus thuringiensis (Bt) toxins are used to manage this pest. NCR with resistance to Bt corn was reported previously in North Dakota and increased use of rootworm Bt corn hybrids could facilitate resistance evolution in other maize-producing states. In this study, susceptibility to Bt proteins was evaluated in wild NCR populations from eight fields collected in five different states (Minnesota, Missouri, Nebraska, Iowa, and North Dakota). The Minnesota population was resistant to Bt and one of the Iowa populations was developing resistance while other populations remained susceptible. Since we found resistance in Minnesota, continued monitoring is needed to assist growers in managing this pest.

Technical Abstract: The northern corn rootworm, Diabrotica barberi Smith & Lawrence (Coleoptera: Chrysomelidae) is a major pest of maize in the United States Corn Belt. Recently, resistance to Bacillus thuringiensis (Bt) maize was reported in North Dakota and increased use of Bt maize hybrids could facilitate resistance evolution in other maize-producing states. In this study, susceptibility to Bt proteins was evaluated in wild D. barberi populations from 8 fields collected in 5 different states (Minnesota, Missouri, Nebraska, Iowa, and North Dakota). Field populations were compared to a susceptible D. barberi colony in seedling and diet toxicity assays conducted with 3 concentrations of Cry3Bb1 (0.4, 4.0, and 40.0 µg/cm2) and Gpp34/Tpp35Ab1 (previously called Cry34/35Ab1; 1.4, 14.0, and 140.0 µg/cm2). The 2019 population from Meeker Co., Minnesota (MN-2019), exhibited the lowest mortality to Cry3Bb1 and also had nominally lowest mortality to Gpp34/Tpp35Ab1 at the highest concentrations tested in diet toxicity assays. Percent second instar was also highest for larvae of the Minnesota population surviving Cry3Bb1. In seedling assays, MN and IA-2018 populations exhibited the highest proportion survival and dry weight to both proteins expressed in corn. No significant differences in mortality, percent second instar, and dry weight were observed at the highest concentration for both proteins among the populations collected in in 2020. Most D. barberi populations were still highly susceptible to Cry3Bb1 and Gpp34/Tpp35Ab1 proteins based on diet and seedling assays, but resistance appears to be developing in some D. barberi populations. Now that methods are available, resistance monitoring may also be needed for D. barberi in some regions.