Behavioural hormoligosis in oviposition preference of Bemisia tabaci (Gennadius) in Bt cotton

The impact of biorationals (flonicamid, pyriproxyfen, spiromesifen) and conventional insecticides (fipronil, bifenthrin and ethion) was evaluated in term of oviposition preference by whitefly to treated cotton plants by multiple-choice test during 2018 and 2019. Whitefly had significantly higher oviposition preference towards plants treated with bifenthrin at 900 ml/ha (186.67eggs/leaf) and fipronil at 1000 ml/ha (171.33eggs/leaf) over untreated control (100.67eggs/leaf) based on overall mean of two years data. However, it showed least preference towards plant treated with spiromesifen at 500 ml/ha (32.11eggs/leaf), flonicamid at 200 g/ha (35.22eggs/leaf) and pyriproxyfen at 1250 ml/ha (53.28eggs/leaf). The results obtained from biochemical studies revealed that bifenthrin and fipronil treated leaves showed significant increase in total soluble sugar, reducing sugar content whereas total phenol and tannin content was significantly decreased in bifenthrin treated leaves. Biochemical parameters like total sugars and reducing sugars showed significant positive correlation; phenols and tannins had significant negative relationship with oviposition preference of whitefly. It may be concluded that bifenthrin and fipronil treated Bt cotton plants are nutritionally superior host for whitefly and led to behavioural hormoligosis in oviposition preference by whitefly.