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ARS Home » Southeast Area » Stoneville, Mississippi » Southern Insect Management Research » Research » Publications at this Location » Publication #396430
Research Project: Ecologically Sustainable Approaches to Insect Resistance Management in Bt Cotton

Location: Southern Insect Management Research

Title: Development of economic thresholds toward bollworm (lepidoptera: noctuidae), management in Bt cotton, and assessment of the benefits from treating Bt cotton with insecticide

Author
item CALVIN, W - Texas A&M University
item YANG, F - Texas A&M University
item BROWN, S.A. - Louisiana State University
item CATCHOT, A.L. - Mississippi State University
item CROW, W.D. - Mississippi State University
item COOK, D.R. - Mississippi State University
item GORE, J. - Mississippi State University
item KURTZ, R. - Cotton, Inc
item LORENZ, G.M. - University Of Arkansas
item SEITER, N.J. - University Of Illinois

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/25/2021
Publication Date: 10/9/2021
Citation: Calvin, W., Yang, F., Brown, S., Catchot, A., Crow, W., Cook, D., Gore, J., Kurtz, R., Lorenz, G., Seiter, N. 2021. Development of economic thresholds toward bollworm (Lepidoptera: Noctuidae), management in Bt cotton, and assessment of the benefits from treating Bt cotton with insecticide. Journal of Economic Entomology. 114:2493-2504. https://doi.org/10.1093/jee/toab173.
DOI: https://doi.org/10.1093/jee/toab173

Interpretive Summary: The introduction of transgenic cotton expressing insecticidal proteins from Bacillus thuringiensis (Bt) in 1996 ushered in a new era in cotton insect pest management. Currently, Bt cotton comprises approximately 90% of U.S. cotton acreage. Widespread field-evolved resistance of bollworm to Cry1 and Cry2 Bt proteins has threatened the utility of Bt cotton for managing bollworm. Field experiments were conducted across the Mid-South and in Texas to devise economic thresholds for foliar insecticide applications targeting bollworm in several Bt cotton technologies and in non-Bt cotton. Selection of the 6% fruiting form injury threshold resulted in a 25 and 75% reduction in insecticide applications relative to preventive sprays for WideStrike and Bollgard II cotton, respectively. All Bt technologies tested in the current study exhibited a positive increase in yield from insecticide application. The frequency of yield increase from spraying WS was comparable to that of NBT. Significant yield increases due to insecticide application occurred less frequently in triple-gene Bt cotton. However, their frequencies were close to the dual-gene Bt cotton, except for WideStrike. The results of our study suggest that 6% fruiting form injury is a viable threshold, and incorporating a vetted economic threshold into an Integrated Pest Management program targeting bollworm should improve the sustainability of cotton production.

Technical Abstract: Widespread field-evolved resistance of bollworm [Helicoverpa zea (Boddie)] to Cry1 and Cry2 Bt proteins has threatened the utility of Bt cotton for managing bollworm. Consequently, foliar insecticide applications have been widely adopted to provide necessary additional control. Field experiments were conducted across the Mid-South and in Texas to devise economic thresholds for foliar insecticide applications targeting bollworm in cotton. Bt cotton technologies including TwinLink (TL; Cry1Ab+Cry2Ae), TwinLink Plus (TLP; Cry1Ab+Cry2Ae+Vip3Aa), Bollgard II (BG2; Cry1Ac+Cry2Ab), Bollgard 3 (BG3; Cry1Ac+Cry2Ab+Vip3Aa), WideStrike (WS; Cry1Ac+Cry1F), WideStrike 3 (WS3; Cry1Ac+Cry1F+Vip3Aa), and a non-Bt (NBT) variety were evaluated. Gain threshold, economic injury level, and economic thresholds were determined. A 6% fruiting form injury threshold was selected and compared with preventive treatments utilizing chlorantraniliprole. Additionally, the differences in yield from spraying bollworms was compared among Bt cotton technologies. The 6% fruiting form injury threshold resulted in a 25 and 75% reduction in insecticide applications relative to preventive sprays for WS and BG2, respectively. All Bt technologies tested in the current study exhibited a positive increase in yield from insecticide application. The frequency of yield increase from spraying WS was comparable to that of NBT. Significant yield increases due to insecticide application occurred less frequently in triple-gene Bt cotton. However, their frequencies were close to the dual-gene Bt cotton, except for WS. The results of our study suggest that 6% fruiting form injury is a viable threshold, and incorporating a vetted economic threshold into an Integrated Pest Management program targeting bollworm should improve the sustainability of cotton production.