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. 2018 Dec 14;111(6):2717-2726.
doi: 10.1093/jee/toy250.

Field Study Investigating Cry51Aa2.834_16 in Cotton for Control of Thrips (Thysanoptera: Thripidae) and Tarnished Plant Bugs (Hemiptera: Miridae)

Scott H Graham  1 , Scott D Stewart  1
Affiliations

Field Study Investigating Cry51Aa2.834_16 in Cotton for Control of Thrips (Thysanoptera: Thripidae) and Tarnished Plant Bugs (Hemiptera: Miridae)

Scott H Graham et al. J Econ Entomol. .

Abstract

Field experiments were conducted in 2016 and 2017 in Tennessee to evaluate the effects of a novel Bacillus thuringiensis (Bt)-transgenic toxin, Bt Cry51Aa2.834_16, on thrips (Thysanoptera: Thripidae) and tarnished plant bug, Lygus lineolaris (Palisot De Beauvois) (Hemiptera: Miridae), in cotton. Protection from thrips injury with the Bt trait was as good or better than an insecticide-based approach. The use of the Bt trait resulted in reduced numbers of immature tarnished plant bug, particularly large nymphs, and partial protection from plant bug injury. Cotton that expressed Bt Cry51Aa2.834_16 had greater yields than the non-Bt isoline when insecticides were not used. Although Bt Cry51Aa2.834_16 reduced the need for insecticide applications, foliar-applied insecticide applications were needed to provide adequate plant protection from tarnished plant bug. The currently recommended treatment thresholds for tarnished plant bug performed similarly well for Bt Cry51Aa2.834_16 and non-Bt isolines. Insecticide applications for tarnished plant bug increased fiber quality, while Bt Cry51Aa2.834_16 had minor effects. The Bt-transgenic toxin Cry51Aa2.834_16 is expected to reduce the need for insecticide applications targeting thrips and tarnished plant bug and could be a valuable addition to an overall insect management program in cotton.

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Figures

Fig. 1.
Fig. 1.
Average total number of (A) thrips per five plants, (B) average thrips injury rating, (C) average aboveground biomass per five plants, and (D) average vigor ratings for Bt Cry51Aa2and non-Bt cotton, with and without an IST averaged across 2 yr and two locations. Error bars represent 95% confidence intervals. Common letters above bars indicate treatments are not different (Fisher’s protected LSD, α = 0.05). Visual rating of thrips injury on a 0–5 scale where 0 represents no injury to any plant in a plot. Visual rating of plant vigor on a 0–5 scale where 0 indicates no living plants in a plot.
Fig. 2.
Fig. 2.
Total number of foliar insecticide applications made to manage tarnished plant bugs in Bt Cry51Aa2 and non-Bt cotton managed using a threshold approach, with and without an IST in (A) Jackson and (B) Milan, TN.
Fig. 3.
Fig. 3.
Average total number of tarnished plant bug nymphs found per 3.02 m row (SEM) of blooming cotton averaged across 2 yr and two locations. (A) Cotton with and without an IST and managed for tarnished plant bug with different spray regimens (automatic [auto], threshold or none). (B) Bt Cry51Aa2 and non-Bt cotton managed for tarnished plant bug with different spray regimens. Error bars represent 95% confidence intervals. Common letters above bars indicate treatments are not different (Fisher’s protected LSD, α = 0.05). *Interaction of trait and spray regimen for total nymphs approached significance (P = 0.0591).
Fig. 4.
Fig. 4.
(A) Average total kilograms of seed-cotton per hectare for Bt Cry51Aa2 and non-Bt cotton treat with and without an IST averaged across 2 yr and two locations. (B) Average total kilograms of seed-cotton per hectare for Bt Cry51Aa2 and non-Bt cotton managed for tarnished plant bug with different spray regimens (automatic [auto], threshold or none) averaged across 2 yr and two locations. Error bars represent 95% confidence intervals. Common letters above bars indicate treatments are not different (Fisher’s protected LSD, α = 0.05).
Fig. 5.
Fig. 5.
Influence of Bt Cry51Aa2 and non-Bt cotton managed for tarnished using different spray regimens (automatic [auto], threshold or none) on average cotton fiber quality indices averaged across 2 yr and two locations. Error bars represent 95% confidence intervals. Common letters above bars indicate treatments are not different (Fisher’s protected LSD, α = 0.05).
Fig. 6.
Fig. 6.
Average pre-bloom percent square retention graphed by 1) tarnished plant bug spray regimens (automatic [auto], threshold [thresh] or none), 2) trait (Bt Cry51Aa2 or non-Bt) and 3) IST (IST or no IST), averaged across 2 yr and two locations. Error bars represent 95% confidence intervals. Common letters above bars indicate treatments are not different (Fisher’s protected LSD, α = 0.05).
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