Transgenic Cotton Age Effects On Lepidopteran Larvae Mortality

Four cotton Bt traits (non-Bt, Bollgard, Bollgard II, and WideStrike) were grown in the field plots and bioassyed in the laboratory against bollworm, beet armyworm, and cabbage looper. Leaves from the middle of the plants were collected every 20 d, starting at 40 d after cotton was planted (DAP) and until 120 DAP.  Leaves from each collection were used for daily feeding about 20 neonate larvae of each species insects before they died.  The higest mortality was showed on dual Bt type.  It was not significantly different both dual Bt traits, Bollgard II and WideStrike, during the growing season.  Mean lifetime larvae and pupae weight were significantly higher on non-Bt cotton.