Weather factors influencing population dynamics of major insect pests of cotton under semi arid agro-ecosystem.

摘要

Experiments were conducted during kharif 2001 and 2002 to evaluate the relationship between the population dynamics of insect pests of cotton and the weather parameters in the semi-arid agroecosystem of Rajasthan, India. The results revealed that the infestation of spotted bollworm (Earias insulana and E. vittella) started in the second fortnight of June and reached its peak (25%) in the first week of August and first week of October. The infestation of pink bollworm (Pectinophora gossypiella) started in the second fortnight of July and reached its maximum (9.75%) in the last week of September and first week of October. The incidence of American bollworm (Helicoverpa armigera) was recorded from the middle of August and reached its peak (8.25%) in the middle of October. The infestation of all the three bollworms lasted until crop harvest. The incidence of jassid (Amrasca biguttula biguttula) started from the second and third week of June and reached its peak (90/30 leaves) in August. The incidence of whitefly (Bemisia tabaci) started in the second and third week of June and reached its peak in the first week of October and remained throughout the growth period of the crop. The minimum temperature had negative significant effect on all the three bollworms, while evening relative humidity (RH) showed negative significant effect on all the three bollworms during 2001 only. The maximum temperature had negative significant and morning and evening RH showed positive significant effect on jassid population, whereas the maximum temperature had positive significant and evening RH exerted negative significant effect on whitefly population.