Vol. 11, Issue 7 (2022)

Author(s):
AV Desai, HR Desai, RD Patel and GR Bhanderi

Abstract:
The present investigations on population dynamics of mealybug, Phenacoccus solenopsis Tinsley and its natural enemies on Bt cotton was carried out at Main Cotton Research Station, Navsari Agricultural University, Surat, Gujarat during Kharif, 2020-21 and 2021-22. Mealybug incidence initiated during 34^th SMW and found gradually increasing after cessation of rain and reached to peak in 52^th SMW. The intensity of infestation within total plants and infested plants were found to range from 0.00 to 10.00 and 0.00 to 37.50 percent, respectively showing maximum intensity at the end of the crop period under untreated condition during the both year. With respect to weather parameters, morning relative humidity, evening relative humidity, average relative humidity, rainfall and rainy days showed significant negative correlation while sunshine hour had positive association with mealybug incidence. Thus, an almost similar result was noticed with respect to incidence of mealybug in relation to weather parameters during both the years. The activity of A. bambawalei was active from 35^th or 36^th SMW to 2^nd or 4^th SMW. Parasitizing activity was higher during December and January months during the both the years. The activity of parasitiod was found to coincide with the population build-up of mealybug and there was significant positive correlation between parasitiod and mealybug populations. The activity of parasitoid showed significant negative correlations with minimum temperature, average temperature, morning humidity, evening humidity, average relative humidity and rainy days and positive correlation with sunshine hour. The activity of coccinellids was observed from 30^th or 32^nd SMW to 2^nd or 4^th SMW during 2020-22. The incidence of coccinellids coincided with mealybug population build up and the association was found significant. Minimum temperature, morning and evening relative humidity and rainy days adversely affected the coccinellids population. The sunshine hour’s favours the population build-up of coccinellids by showing significant positive relationship during the both years. The activity of Chrysoperla was not influenced by mealybug population and the activity was noticed mainly with aphids. The sunshine hours favours the population build-up of Chrysoperla by showing significant positive relationship during the both years.