Insecticide resistance in whitefly, Bemisia tabaci (Gennadius) on Cotton in Punjab

Populations of whitefly, Bemisia tabaci from different locations viz., Ludhiana, Mansa, Bathinda and Fazilka were collected and toxicity of four insecticides viz., triazophos, ethion, spiromesifen and diafenthiuron was evaluated. It was compared with its susceptible population maintained for over 20 generations under laboratory conditions. The susceptible population showed the maximum sensitivity to spiromesifen with LC₅₀ of (0.020) while it was minimum with triazophos (0.049). Spiromesifen was the most toxic against the field populations with LC₅₀ as (0.036–0.666) followed by ethion (0.084–0.319), diafenthiuron (0.099–0.277) while triazophos was least effective (0.325–0.943). However, based on LC₉₀ values, ethion was the most toxic (0.173–0.577) followed by spiromesifen (0.336–2.704), diafenthiuron (0.548–1.188) while triazophos was least toxic (0.679–3.735). Whitefly populations from fields of Fazilka showed maximum resistance to spiromesifen followed by triazophos Similarly, Mansa population showed maximum resistance to triazophos followed by spiromesifen while Ludhiana population showed maximum resistance to triazophos followed by diafenthiuron.