Status of insecticide resistance in Spodoptera litura occurring on groundnut in Andhra Pradesh and Telangana

Bioassay studies were carried out on different populations of tobacco caterpillar, Spodoptera litura (Fab.) (Lepidoptera: Noctuidae) collected from nine locations in Andhra Pradesh and Telangana, India during Rabi 2012–2013 and 2013–2014 from farmers groundnut fields. The F₂ generations were screened for resistance to commonly used insecticides in field. Resistance levels ranged as follows: cypermethrin, 6.43 to 20.93 fold; lambdacyhalothrin, 4.55 to 26.21 fold; quinalphos, 15.65 to 20.93 fold; chlorpyriphos, 16.81 to 22.10 fold; acephate, 15.67 to 23.32 fold and indoxacarb, 2.40 to 21.80 fold. Among different larval populations of S.litura, high level of resistance was found in population from Guntur followed by Karimnagar and Kurnool with highest LC₅₀ and LC₉₀ values at 48 hours after treatment (HAT). Population from Anantapuramu, Kadapa, Nellore, Chittoor, Mahaboobnagar and Warangal were found to possess moderate levels of resistance as compared to baseline population on the basis of LC₅₀ and LC₉₀ values recorded 48 hours after treatment.