This study was conducted to evaluate the efficiency of three plant extracts i. e. NeemAzal, soybean and garlic (8iorepel) and five insect growth regulators (IGRs) i. e. Consult, Atabron, Cascade, Match and Mimic using the recommended field rate to control the cotton leafworm in cotton and Egyptian clover fields at Zagazig region, Sharida Governorate in 1999 and 2000 seasons. Plant extracts: NeemAzal recorded the highest initial and residual reduction percentages in both seasons in cotton fields, the highest initial reduction reached 30.33% whereas the highest residual reduction was 39.88%. However, in clover fields the highest initial reduction reached 32.11% in 1999 season with 8iorepel, whereas NeemAzal recorded the highest residual reduction percentage In the same season (36.03%). As for the initial and residual reduction percentages in 2000 season (25.99 and 38.63%, respectively. IGRs, The initial reduction percentages did not record reduction percentages 92.00% in both crops for the all tested compounds except Mimic which recorded initial reduction percentages less than 77.00% in 1999 season in cotton field, while the residual reduction did not rise than 87.00% in 2000 season As a general trend, the 1GR Atabron is considered the most effective in reducing the pest population Changes in total soluble protein, transaminase enzymes (GOT and GPT) and carbohydrate hydrolyzing enzymes (amylase, invertase and trehalase) activities in the 4th instar larvae of the cotton leafworm, Spodoptera Illtotalis (8oisd) as affected by plant extracts laboratory application were studied. Results appeared at the following Poundings.