Seasonal incidence of the sucking pest and lady bird beetle on Bt cotton

Abstract

Seasonal incidence of sucking pests in Kharif 2016 at College of Agriculture, Dhule revealed that, the leafhopper incidence reached its peak activity during the second week of October (6.64 leafhoppers/3 leaves/plant), whereas, the peak incidence of aphids was noticed in the third week of October (8.82 aphids/3 leaves/plant). The peak incidence of the whiteflies was recorded during the fourth week of October (8.02 whiteflies/3 leaves/plant). The peak incidence of the thrips was recorded during the third week of October (6.76 thrips/3 leaves/plant). The activity of predator lady bird beetle was at its peak during first week of October (2.94 lady bird beetles/plant), which is directly related with the activity of the sucking pest in field. The correlation between incidence of leaf hoppers (r = 0.205), aphids (r = 0.174), whiteflies (r = 0.206), thrips (r = 0.167), was positively non-significant with maximum temperature (T max ). The minimum temperature (T min ) showed negative significant correlation with whiteflies (r = -0.640**), thrips (r =-0.464*) and negative non-significant correlation with leafhoppers(r =-0.411) and aphids (r = -0.3111). The morning relative humidity (MRH) showed negative significant correlation with occurrence of whiteflies (r = -0.440*) and negative non significant correlation with occurrence of the leafhoppers(r = -0.123), aphids (r = -0.101) and thrips (r = -0.184). Similarly, the evening humidity (ERH) showed negative non significant correlation with the pests such as leafhoppers(r = -0.038), aphids (r = -0.021), whiteflies (r = -0.166) and thrips (r = -0.085) during Kharif 2016 season. The rainfall had negatively non significant effect at 5 per cent level of significance with leafhoppers, aphids, whitefly and thrips.