Toxicity of Different Groups of Insecticides Against First, Second and Third Instar Larvae of Cotton Bollworm, Helicoverpa armigera (Hub.) (Lepidoptera: Noctuidae)

Four commercial insecticides viz . curacran 500 EC (Profenophos) @ 1.0 ml/100 ml, somialfa 110 EC (esfenvalerate) @ 0.25 ml/100 ml, decis 2.5 EC (deltamethrin) @ 2.25 ml/100 ml and denitol 30 EC (fenpropathrin) @ 0.25 ml/100 ml were tested at field dose under laboratory conditions for their toxicity against cotton bollworm, H. armigera (Hub.) larvae of (1 st , 2 nd and 3 rd ) instar. Insect mortality data were taken after 24, 48 and 72 hours exposure and then subjected to ANOVA. Results showed that curacron 500 EC and somialfa 110 EC were highly effective by causing 100 and 80% mortality after 24 hours exposure which reached to 100% each after 72 hours exposure. Both these insecticides caused 100% mortality after 24, 48 and 72 hours exposure of 2 nd instar larvae. Only curacron was effective against 3 rd instar larvae by causing 25, 100 and 100% mortality after an exposure of 24, 48 and 72 hours. Decis and denitol were effective on 1 st instar larvae by causing mortalities of 43.3 to 83.3 and 45 to 85% after collective exposure of 72 hours, whereas no substantial mortality was observed in 2 nd and 3 rd instar larvae. It is concluded from the results that curacron was highly effective against 1 st , 2 nd an 3 rd instar larvae followed by somialfa.