الفهرس 
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Abstract
The present study aimed to evaluated the toxicity of Insect Growth Regulators (IGRs), including chlorfluazuron, hexaflumuron and diflubenzuron against the 4th and 6th larval instars of Egyptian cotton leaf worm , Spodoptera littoralis based on LC50 values using leaf dipping technique, it is clear that the chlorfluazuron was more toxic than hexaflumuron and diflubenzuron, also three methods of application (Topical application, Injection and Oral) were studied on 5th instar larvae of Spodoptera littoralis using chlorfluazuron. Topical application was most toxic based on LD50. The treatment with tested compounds affected some biological parameters of Spodoptera littorallis and food consumption for 4th instar larvae. Chlorfluazuron and hexaflumuron decreased food consumption and growth rate of 4th instar larvae of S. littoralis. The larval and pupal durations were prolonged while, the pupation, emergence of adults, fecundity and hatchability were reduced significantly using leaf dipping technique, while topical application caused reduction in longevity of female moth, hatchability and sterility on the otherhand, injection method caused reduction in fecundity. Some morphological abnormalities in larvae, pupae and adults were recorded. In addition, the disturbance in enzymes activities, e.g. AST, ALT, amylase, invertase, trehalase enzymes was detected.