Field evaluation of Bt cotton hybrids against insect pest complex under rain fed conditions

The field performance of certain released Bt cotton hybrids for their reaction to pest complex were evaluated in comparison with their non Bt counterparts for two consecutive seasons at Regional Agricultural Research Station, Lam, Guntur under rainfed conditions. The present study showed that there were no much differences between Bt and non Bt versions of the same hybrid regarding the incidence of sucking pests though there were differences among the hybrids. The RCH 2 hybrid showed relative tolerance to thrips and whiteflies, Mallika hybrid to aphids and leafhoppers, while Bunny hybrid against whiteflies irrespective of Bt or non Bt version. Proagro 368 Bt hybrid showed susceptible reactions to aphids and Bunny Bt hybrid to thrips. The Bt hybrids were found highly resistant against both American bollworm and pink bollworm with very low larval population, square damage and locule damage in green bolls. The population of natural enemies was slightly higher in Bt versions indicated that there was no adverse effects of Cry 1Ac gene against natural enemies. There were no significant differences in fiber properties between Bt and non Bt versions of the same hybrid.