Evaluation of current tarnished plant bug (Hemiptera: Miridae) thresholds in transgenic mon 88702 cotton expressing the Bt Cry51Aa2.834_16 trait

Authors: CORBIN, J.C. - Mississippi State University; TOWLES, T.B - Mississippi State University; CROW, WHITNEY - Mississippi State University; CATCHOT, ANGUS - Mississippi State University; COOK, DON - Mississippi State University; DODDS, D.M. - Mississippi State University; GORE, J. - Mississippi State University

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/26/2020
Publication Date: 4/25/2020
Citation: Corbin, J., Towles, T., Crow, W.D., Catchot, A.L., Cook, D.R., Dodds, D., Gore, J. 2020. Evaluation of current tarnished plant bug (Hemiptera: Miridae) thresholds in transgenic mon 88702 cotton expressing the Bt Cry51Aa2.834_16 trait. Journal of Economic Entomology. 113(4):1816-1822. https://doi.org/10.1093/jee/toaa075.
DOI: https://doi.org/10.1093/jee/toaa075

Interpretive Summary: The tarnished plant bug is an important pest of cotton in many areas of the southern United States. An experiment was conducted at two locations in Mississippi during 2016 and 2017 to evaluate the appropriate time to initiate insecticidal control for tarnished plant bug (action threshold) on a novel cotton expressing the soil bacterium, Bacillus thuringiensis (Bt cotton). Treatments included the current action threshold, a 2× threshold, and treatments where insecticides were only applied during the early season (preflower) or only during late season (during flowering) based on the current action thresholds. These were compared to an untreated control and a weekly insecticide use regime that received weekly insecticide sprays. All treatments were imposed on both the new Bt cotton and a nontraited cotton. The Bt cotton trait reduced the number of tarnished plant bugs and injury, and improved yields compared to nontraited cotton. For all spray treatments except the weekly insecticide use regime, yields were greater for the Bt cotton than the nontraited cotton. In terms of thresholds, Bt cotton cotton sprayed based on current action thresholds resulted in similar yields to the weekly insecticide use regime of both cotton types. In contrast, the 2× threshold resulted in lower yields than the current threshold for both cotton types. Though thresholds intermediate to the currently recommended action threshold and the 2× threshold were not tested, these data suggest that currently recommended action thresholds appear appropriate for the novel Bt cotton. These results suggest that this trait will be an important component of current IPM programs in cotton where tarnished plant bug is an important pest.

Technical Abstract: The tarnished plant bug, Lygus lineolaris (Palisot de Beauvois), is an important pest of cotton in many areas of the southern United States. An experiment was conducted at two locations in Mississippi during 2016 and 2017 to evaluate action thresholds for tarnished plant bug on a novel Bacillus thuringiensis cotton that expresses the Cry51Aa2.834_16 toxin. Treatments included the current action threshold, a 2× threshold, and treatments where insecticides were only applied during the early season (preflower) or only during late season (during flowering) based on the current action thresholds. These were compared to an untreated control and a weekly insecticide use regime that received weekly insecticide sprays. All treatments were imposed on both Bt Cry1Aa2.834_16 cotton and a nontraited cotton. The Bt Cry1Aa2.834_16 trait reduced the number of tarnished plant bugs and injury, and improved yields compared to nontraited cotton. For all spray treatments except the weekly insecticide use regime, yields were greater for the Bt Cry51Aa2.834_16 cotton than the nontraited cotton. In terms of thresholds, Bt Cry1Aa2.834_16 cotton sprayed based on current action thresholds resulted in similar yields to the weekly insecticide use regime of both cotton types. In contrast, the 2× threshold resulted in lower yields than the current threshold for both cotton types. Though thresholds intermediate to the currently recommended action threshold and the 2× threshold were not tested, these data suggest that currently recommended action thresholds appear appropriate for Bt Cry51Aa2.834_16 cotton. These results suggest that this trait will be an important component of current IPM programs in cotton where tarnished plant bug is an important pest.