Seasonal incidence of yellow mite, Polyphagotarsonemus latus (Banks) in Bt cotton and their correlation with weather parameters

摘要

The population fluctuation studies on yellow mite were conducted during Kharif 2017 and 2018 seasons usingMRC 7351 Bt cotton raised under the unprotected condition. The egg and active stage incidence of yellow mite started from 29 th(2.55 yellow mite egg/ leaf) and 30 th MSW (1.64 yellow mite/ leaf), respectively and reached the maximum population at 34 thMSW (4.14 yellow mite/ leaf). Whereas, the leaf curl index due to yellow mite commenced from 31 st MSW (1.68 LCI) andattained a peak of 2.78 LCI at 34 th MSW. Thereafter, the LCI decreased. Predatory mite activity noticed from 31 st MSW (0.11predatory mite/ leaf) and reached the maximum at 34 th MSW (0.95 predatory mite/ leaf). Weather parameters correlation withyellow mite egg, active stages and leaf curl index showed negative and non-significant association with maximum temperaturebut the positive and non-significant relationship with minimum temperature and rainfall whereas maximum relative humidity,minimum relative humidity and predatory mite were positively correlated and showed a significant relationship.