The studies were conducted to study the population dynamics, correlation and regression between weather parameters and spotted bollworm, American bollworm and pink bollworm on cotton under high density planting system. The population fluctuation of spotted bollworm (Earias vitella Fab) during kharif 2013-14 ranged from 0.1 to 0.15 larvae / plant. The incidence started from 33^th MW (0.15 larvae/plant) and its peak was observed during 34^th MW (0.2 larvae / plant). Whereas the population of American bollworm (Helicoverpa armigera Hubner) during Kharif 2013-14 fluctuated between 0.1 to 1.25 larvae/plant. The incidence of American bollworm started from 35^th MW (0.1Larvae / plant) and its peak was observed during 39^th MW (1.25 larvae / plant) with highest fruiting damage 7.25 per cent. The population of Pink Bollworm (Pectinophora gossypiella Saund.) ranged between 1 to 2 no. larvae / 20 boll the incidence of Pink bollworm initiated from 45th MW (1 larvae / 20 bolls) and the peak activity was noticed during 47^th MW (2 larvae / 20 bolls).