Seasonal abundance of sucking insect pests on transgenic<i>Bt</i>cotton vis-à-vis weather parameters in Punjab, India

Abstract

Among sucking insect pests, the incidence of a leafhopper [Amrasca biguttula biguttula (Ishida)] and a whitefly [Bemisia tabaci (Gennadius)] remained active through the cropping season in varying population density. Thrips [Thrips tabaci (Lindemann)] population was only observed in early stages of the crop growth. The leafhopper population attained its peak during 2nd half of July and was maximum (9.2 nymphs/3 leaves) in the year 2008. The population of whitefly adults was maximum (14.8 adults/3 leaves) in 2007 and it acquired its peak during end of July and again in end of September to early October. The incidence of thrips was maximum in June. The population of the A. biguttula showed significant positive correlation with minimum temperature (r=0.636; p=0.003), mean temperature (r=0.475; p=0.034), evening relative humidity (r=0.618; p=0.004) and rainfall (r=0.556; p=0.011). The correlation of B. tabaci population with minimum temperature was significantly positive (r=0.454; p=0.044). The multiple regression analysis revealed that all the weather parameters collectively accounted for variability in the A. biguttula and B. tabaci population with R2 values ranging from 0.67–0.80 and 0.50–0.69, respectively, during different years.