Monitoring of resistance to conventional insecticides in field populations of Aphis gossypii glover from major cotton growing areas of Vidarbha

The insecticide resistance was assayed for field collected Aphis gossypii populations from Yavatmal, Amravati, Akola, Wardha and Buldhana districts of Vidarbha (MS) by leaf dip method. The results indicated that the three insecticides tested viz., Acetamiprid 20 SP, Methyl demeton 25 EC and Dimethoate 30 EC were less toxic to Yavatmal and Amravati populations of Aphis gossypii recording higher LC50 and LC90 values. The relative toxicity studies amongst insecticides reveled that Dimethoate 30 EC was highly toxic to aphid population from five districts with RT values of 1.00 followed by Methyl demeton (0.49 to 0.53) and Acetamiprid (0.31 to 0.39) indicating that the resistance to these insecticides not varied much amongst the five geographical regions. The studies on relative degree of resistance revealed that the Aphis gossypii populations from Yavatmal district registered highest degree of resistance with resistance ratios (RR) ranging 1.05 to 1.48 fold against Acetamiprid 1.26 to 1.53 against Dimethoate and 1.24 to 1.47 against Methyl demeton as compared with aphid populations from Buldhana, Wardha, Akola and Amravati districts. The aphid populations from Buldhana district seems to be more susceptible against all the three insecticides tested as compared to aphids populations from other four districts.