author(s)
E Akhila, S Upendhar, K Vani Sree and B Vidhya Sagar

abstract
The present study aimed at the screening of popular Bt cotton hybrids against aphid, Aphis gossypii (Glover) incidence at College farm, College of Agriculture, Rajendranagar, Hyderabad during kharif 2019-20. Eight transgenic cotton hybrids (Bioseed-7215-2, MH-5343, RCH-668, MRC-7347, PRCH-331, RCH-386, ROHINI-456, RCH-659) were sown and maintained without application of any insecticide till the maturity of the crop. Field data of aphids were collected from the occurrence of the pests after seedling emergence to till the harvest at weekly intervals. The results revealed that 34^th, 35^th, 36^th, 51^st and 52^nd standard weeks were the most favourable for aphid incidence. The peak incidence of aphid population (18.56/3 leaves/plant) was recorded during 34^th standard week in RCH-659. In correlation studies, aphid population showed negative correlation with the majority of abiotic factors. Particularly, the aphid population showed a non-significant negative correlation with maximum temperature, relative humidity, rainfall while the positive correlation with minimum temperature in most of the hybrids. The multiple linear regression studies revealed that all the weather parameters together contribute 31 percent (R²=0.31) of the total variation in the aphid population.