Toxicity of diamide and spinosyn insecticides against tobacco caterpillar Spodoptera litura (F.)

The stomach and contact toxicity of diamide (chlorantraniliprole and flubendiamide) and spinosyn (spinetoram and spinosad) insecticides were evaluated against 4 days old larvae of Spodoptera litura (F.) by leaf smear and larval atomization methods on castor leaf disc under laboratory conditions (25 ± 2°C, 75 ± 5% RH, September-October, 2018). The order of toxicity was observed as: chlorantraniliprole (LC₅₀= 0.00086) > spinetoram (0.0034) > flubendiamide (0.005) > spinosad (0.02%) at 48 hr after exposure (HAE) by larval atomization method and chlorantraniliprole (LC₅₀= 0.0042 and 0.0009) > spinetoram (0.0047 and 0.0032) > spinosad (0.0316 and 0.0182%) at 24 and 36 hr after feeding (HAF) by leaf smear method. Chlorantraniliprole exhibited 1.24 times more stomach toxicity by leaf smear method (LC₅₀ = 0.0009%) than contact toxicity by larval atomization method (LC₅₀= 0.00112%) at 36 HAF/HAE. The stomach toxicity (LC₅₀= 0.0047 and 0.0032%) of spinetoram was 2.57 and 2.66 times more than the contact toxicity (0.0121 and 0.0085%) at 24 and 36 HAF/HAE. Spinosad also showed 1.24 and 1.82 times more stomach toxicity (LC₅₀= 0.0182 and 0.0110%) than the contact toxicity (0.0225 and 0.02%) at 36 and 48 HAF/HAE, respectively.