Toxicological and Biological Studies on Using Lufenuron, Chlorpyrifos, Spinosad and Emamectin Benzoate Insecticides for Controlling Cotton Leafworm, Spodoptera littoralis (Boisd.)

This study was evaluated the toxicity and latent effect of four insecticides; chlorpyrifos (Dursban H 48% EC) as organophosphates, emamectin benzoate (Proclaim 5% SG) as bioinsecticide, lufenuron (Match 5% E.C) as IGR and spinosad (Spintor 24% SC) as bioinsecticide against 2nd and 4th instar larvae of the cotton leafworm, Spodoptera litraltois lab and field strain. The present data proved that values of LC₅₀ for second instar larval were 1.04, 1.16, 2.73 and 3.12 ppm for 2nd instar larvae for lab strain, while values of LC₅₀ increased to 2.94, 2.86, 3.26 and 4.96 ppm for field strain when treated larvae with chlorpyrifos, emamectin benzoate, lufenuron and spinosad, respectively. Moreover, values of LC₅₀ were 3.82, 3.01, 4.54 and 6.28 ppm for 4th instar larvae lab strain, and increased to reach 5.48, 4.95, 6.67 and 9.97 ppm for 4th instar larvae field strain when treated larvae with chlorpyrifos, emamectin benzoate, lufenuron and spinosad, respectively. As for the late effects, the results indicated that in case of second instar larvae the lowest percentage of pupation were 18.55 and 28.56% when treated larvae with lufenuron whereas, the highest 39.55 and 44.23% with spinosad for larvae of lab and field strains, respectively and adult emergence was the lowest when treated larvae with chlorpyrifos, lufenuron and spinosad for lab strains, while larvae of field strains gave the lowest percentage with treated by lufenuron (14.32%) and the mean of eggs /female were the lowest (155.45 egg/female) when treated larvae with lufenuron for lab and field strains and was the lowest (138.0 egg /female) when treated larvae with spinosad for field strain. In case of fourth instar larvae, larvae of lab strain showed the lowest percentage of pupation (31.23%) when treated with spinosad while the lowest percentage of pupation (40.42%) when treated larvae with chlorpyrifos and hatchability percent increase in field strain compare to lab strain.