Evaluation of the Efficacy of Certain Juvenoids on the Tobacco Caterpillar Spodoptera litura

Four juvenoids namely methoprene, hydroprene, fenoxycarb and prodron® and a pyrethroid, cypermethrin were evaluated against the last larval instar of the tobacco caterpillar, Spodoptera litura. Methoprene, hydroprene and cypermethrin were applled topically wheareas fenoxycarb and Prodron® were fed orally. ID₅₀ values for inhibiting adult emergence were 0.027, 68.077 and 273.698 μg g⁻¹ for cypermethrin, methoprene and hydroprene respectively. The oral ID₅₀ values for fenoxycarb and Prodron® were 4.578 and 796.159 μg g-¹ respectively. Cypermethrin at sublethal doses caused juvenomimetic effects. The adults emerging from such treatment had deformed proboscis and abnormal legs. The study brings out a need for field evaluation of fenoxycarb, a potent juvenoid, against lepidopteran pests and also suggests the use of reduced doses of cypermethrin in integrated pest management programmes, giving due consideration for the developmental defects caused.