Biological aspects of Chrysoperla externa (Hagen, 1861) fed with Aphis gossypii (Glover, 1877) from Bt and conventional cotton

Abstract

The objective of this study was to evaluate the biological aspects and predatory capacity of Chrysoperla externa fed with Aphis gossypii from Bt and conventional cotton. The experiment was conducted in a climate-controlled room at 25±1^oC, RH of 70%±10%, in a completely randomized design. The eggs of C. externa were individualized in Petri dishes, and the neonate larvae were fed daily with aphids from nine cotton cultivars, constituting the treatments. The cultivars used were Conventional (without genetic modifications), FM993, DP604 BG (Bollgard I®-Cry1Ac), NuOpal (Bollgard I®-Cry1Ac), DP90 B (Bollgard I®-Cry1Ac), Acala DTL90B (Bollgard I®-Cry1Ac), DP555 BGRR (Bollgard I®-Cry1Ac), DP1228 B2RF (Bollgard II®-Cry1Ac+Cry2Ab2), PHY440 W (WideStrike®-Cry1Ac+Cry1F) and FM975 WS (WideStrike®-Cry1Ac+Cry1F). The duration of the development phase in days, viability in percentage and weight in (mg) of all immature stages were evaluated. For predatory capacity, first, second and third instar larvae were individualized in Petri dishes, receiving the proportion of 1:10; 1:25; 1:50 predator and prey, for each instar respectively. After 24 hours, the predator's consumption potential was quantified. All Bt technologies in which the prey A. gossypii was reared negatively influenced the biological development of C. externa, with the greatest impact being evidenced for the Cry1Ac toxin present in the DP 90B cultivar. The Cry1Ac protein negatively influenced the predatory capacity of C. externa when fed on A. gossypii from the DP 90 cultivar.