Population dynamics of cotton aphid and its predators on Bt cotton and its impact of Bt cotton fed aphids on biology of Chrysoperla cornea Steph.

摘要

The population dynamics of cotton aphid, Aphis gossypii Glover and its predators viz., Cheilomenes sexmaculata Fab., Chrysoperla cornea Steph. and Ischiodon scutellaris Fab. was studied on RCH 2 Bt and non Bt cotton hybrids. The mean number of aphids was 23.82 and 21.37/leaf in RCH 2 Bt and non Bt, respectively, indicating no significant variation. The dynamics of predators was aphid density dependent in both Bt and non Bt hybrids. Mean population of coccinellids, Chrysoperla and syrphids was 0.89, 0.78 and 1.0/plant in RCH 2 Bt which was almost similar to the incidence on RCH 2 non Bt. There was strong and positive correlation between population of predators and aphid on both Bt and non Bt cotton. Laboratory feeding experiments using Bt and non Bt cotton carried out to study the effect of Bt fed aphids on predator C. cornea indicated no difference in incubation period, longevity of grubs and adults, fecundity and aphid consumption potential indicating safety of Cry1Ac to C. cornea through intoxicated aphid host.