Extended Sentinel Monitoring of Helicoverpa zea Resistance to Cry and Vip3Aa Toxins in Bt Sweet Corn: Assessing Changes in Phenotypic and Allele Frequencies of Resistance

Authors

Galen P. Dively, University of Maryland, College ParkFollow
Tom P. Kuhar, Virginia Polytechnic Institute and State University
Sally V. Taylor, Virginia Polytechnic Institute and State University
Helene Doughty, Virginia Tech ESAREC/Entomology
Kristian Holmstrom, Rutgers University–New Brunswick
Daniel O. Gilrein, Cornell University
Brian A. Nault, Cornell AgriTech
Joseph Ingerson-Mahar, Rutgers Agricultural Research and Extension Center
Anders Huseth, NC State University
Dominic Reisig, NC State University
Shelby Fleischer, Pennsylvania State University
David Owens, University of Delaware
Kelley Tilmon, Ohio Agricultural Research and Development Center
Francis Reay-Jones, Clemson University
Pat Porter, Texas A&M AgriLife
Jocelyn Smith, University of Guelph
Julien Saguez, CEROM
Jason Wells, New Brunswick Department of Agriculture
Caitlin Congdon, Perennia Food and Agriculture Inc.
Holly Byker, University of Guelph
Bryan Jensen, University of Wisconsin Madison Agricultural Research Station
Chris DiFonzo, Michigan State University
William D. Hutchison, University of Minnesota Twin Cities
Eric Burkness, University of Minnesota Twin Cities
Robert Wright, University of Nebraska–LincolnFollow
Michael Crossley, University of Delaware
Heather Darby, The University of Vermont
Tom Bilbo, Clemson University
Nicholas Seiter, University of Illinois Urbana-Champaign
Christian Krupke, Purdue University
Craig Abel, Iowa State University
Brad S. Coates, Iowa State University
Bradley McManus, South Dakota State University
Billy Fuller, South Dakota State University
Jeffrey Bradshaw, Panhandle Research and Extension Center
Julie A. Peterson, West Central Research and Extension Center
David Buntin, The University of Georgia Griffin Campus
Silvana Paula-Moraes, University of Florida Institute of Food and Agricultural Sciences
Katelyn Kesheimer, Auburn University
Whitney Crow, Delta Research and Extension Center

Date of this Version

7-1-2023

Citation

Dively, G.P.; Kuhar, T.P.; Taylor, S.V.; Doughty, H.; Holmstrom, K.; Gilrein, D.O.; Nault, B.A.; Ingerson-Mahar, J.; Huseth, A.; Reisig, D.; et al. Extended Sentinel Monitoring of Helicoverpa zea Resistance to Cry and Vip3Aa Toxins in Bt Sweet Corn: Assessing Changes in Phenotypic and Allele Frequencies of Resistance. Insects 2023, 14, 577. https://doi.org/10.3390/ insects14070577

Comments

This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution

Abstract

Transgenic corn and cotton that produce Cry and Vip3Aa toxins derived from Bacillus thuringiensis (Bt) are widely planted in the United States to control lepidopteran pests. The sustainability of these Bt crops is threatened because the corn earworm/bollworm, Helicoverpa zea (Boddie), is evolving a resistance to these toxins. Using Bt sweet corn as a sentinel plant to monitor the evolution of resistance, collaborators established 146 trials in twenty-five states and five Canadian provinces during 2020–2022. The study evaluated overall changes in the phenotypic frequency of resistance (the ratio of larval densities in Bt ears relative to densities in non-Bt ears) in H. zea populations and the range of resistance allele frequencies for Cry1Ab and Vip3Aa. The results revealed a widespread resistance to Cry1Ab, Cry2Ab2, and Cry1A.105 Cry toxins, with higher numbers of larvae surviving in Bt ears than in non-Bt ears at many trial locations. Depending on assumptions about the inheritance of resistance, allele frequencies for Cry1Ab ranged from 0.465 (dominant resistance) to 0.995 (recessive resistance). Although Vip3Aa provided high control efficacy against H. zea, the results show a notable increase in ear damage and a number of surviving older larvae, particularly at southern locations. Assuming recessive resistance, the estimated resistance allele frequencies for Vip3Aa ranged from 0.115 in the Gulf states to 0.032 at more northern locations. These findings indicate that better resistance management practices are urgently needed to sustain efficacy the of corn and cotton that produce Vip3Aa.