Population dynamics of major insect-pests of cotton and their natural enemies

摘要

Studies were conducted at Cotton Research Station, Marathwada Agricultural University, Parbhani during kharif 2004-2005 and 2005-2006. The incidence of aphid (Aphis gossypii Glover), leafhopper (Amrasca biguttula biguttula Ishida), thrips (Thrips tabaci Lind) and whitefly (Bemisia tabaci Gennadius) started in second fortnight of July during both the years. The aphid population reached the peaks in August, September and November during 2004 and 2005. Leafhopper attained its peak during September and October while thrips attained its peak in August and November in both the years. The whitefly incidence was low during 2004, while it attained its peak in second week of November during 2005. The aphid and leafhopper incidence showed significant negativecorrelation with relative humidity. Thrips exhibited significant positive correlation with bright sunshine hours and whitefly showed significant negative correlation with wind velocity. Fruiting bodies damage due to American bollworm and spotted bollwormwas maximum during first week of September 2004 and in second week of September and third week of November during 2005. Incidence of bollworm in green bolls was maximum during third week of September and that of spotted bollworm in first week of December during 2004. The maximum population of ladybird beetle (Coccinella spp.) was recorded in second week of September and November during both the years, while green lace wing (Chrysopa spp.) population was maximum in the second week of October.