Bollworm Behavior in Bt and Non-Bt Cotton

Bollworm is becoming increasingly tolerant and developing practical resistance to different strains of Bt cotton. Behavior of bollworm neonates has proven different between non-Bt and Bt cottons. We initiated a study seeking to understand any behavioral differences of larvae leaving non-Bt and different Bt varieties of cotton, as well as to quantify oviposition and larval numbers within the same varieties. Seven or eight cotton varieties were grown, and 10 plants sampled weekly during bollworm presence. During the same time as sampling, two, 31X36” sticky boards were placed between cotton rows. We found more larvae in non-Bt cotton compared to Bt early during larvae presence, and more larvae in two stack pyramids compared to Vip varieties. Larvae of all stages left all varieties of cotton, with more leaving non-Bt early during sampling.