Landscape-level variation in Bt crops predict Helicoverpa zea (Lepidoptera: Noctuidae) resistance in cotton agroecosystems

Authors: Dorman, Seth; HOPPERSTAD, KRISTEN - North Carolina State University; REICH, BRIAN - North Carolina State University; MAJUMDER, SUMAN - North Carolina State University; KENNEDY, GEORGE - North Carolina State University; REISIG, DOMINIC - North Carolina State University; GREENE, JEREMY - Clemson University; REAY-JONES, FRANCIS - Clemson University; COLLINS, GUY - North Carolina State University; BACHELER, JACK - North Carolina State University; HUSETH, ANDERS - North Carolina State University

Submitted to: Pest Management Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/18/2021
Publication Date: 8/1/2021
Citation: Dorman, S.J., Hopperstad, K.A., Reich, B.J., Majumder, S., Kennedy, G., Reisig, D.D., Greene, J.K., Reay-Jones, F.P., Collins, G., Bacheler, J., Huseth, A.S. 2021. Landscape-level variation in Bt crops predict Helicoverpa zea (Lepidoptera: Noctuidae) resistance in cotton agroecosystems. Pest Management Science. 77(12):5454-5462. https://doi.org/10.1002/ps.6585.
DOI: https://doi.org/10.1002/ps.6585

Interpretive Summary: Near-complete adoption of genetically engineered (GE) crops with Bt technology in the southeastern United States has led to widespread resistance to insect species, including bollworm (Helicoverpa zea Boddie) resistance. Our study surveys commerical cotton fields for bollworm damage to investigate the linkage between Bt crop production intensity at the landscape-level and Bt crop susceptibilty to bollworm damage. Survey data included longitudinal data spanning the Bt crop adoption period, data since Bt resistance has been observed, and data from on-farm studies of cotton varying in Bt toxin profile. We observed significant differences in bollworm damage across years, with pronounced damage after the year 2012. Landscape-level Bt crop production intensity over time was positively associated with the risk of bollworm damage in Bt cotton with two and three toxins. Bollworm damage also varied across Bt toxin types in spatially replicated on-farm studies. Landscape-level predictors of bollworm damage can be used to forecast high-risk areas for resistance to Bt toxins, serving as a model to understand factors that drive pest resistance development to Bt toxins in the southeastern United States. These results provide a framework for more effective insect resistance management (IRM) strategies to be used in combination with conventional pest management practices that improve the longevity of Bt traits while minimizing the environmental footprint of row crop agriculture.

Technical Abstract: Helicoverpa zea (Boddie) damage to Bt cotton and maize has become more severe due to widespread Bt resistance across the USA Cotton Belt. Our objective was to link Bt crop production patterns to cotton damage through a series of spatial and temporal surveys of commercial fields to understand how Bt crop production relates to greater than expected damage to Bt cotton. To do this, we assembled longitudinal cotton damage data that spanned the Bt adoption period, collected cotton damage data since Bt resistance has been detected and estimated local population susceptibility using replicated on-farm studies that included all Bt pyramids marketed in cotton. Significant year effects of H. zea damage frequency in commercial cotton were observed throughout the Bt adoption period, with a recent damage increase after the year 2012. Landscape-level Bt crop production intensity over time was positively associated with the risk of H. zea damage in two- and three-toxin pyramided Bt cotton. Helicoverpa zea damage also varied across Bt toxin types in spatially replicated on-farm studies. Landscape-level predictors of H. zea damage in Bt cotton can be used to forecast heightened Bt resistance risk areas and serves as a model to understand factors that drive pest resistance evolution to Bt toxins in the southeastern United States. These results provide a framework for more effective insect resistance management (IRM) strategies to be used in combination with conventional pest management practices that improve Bt trait durability while minimizing the environmental footprint of row crop agriculture.