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Abstract
Laboratory bioassay tests were carried out on two chitin synthesis inhibitors, flufenoxuron and lufenuron, to find out the effects of Spodoptera littoralis and Agrotis ipsilon 2nd, 4th and 6th instar larval feeding on treated castor-bean leaves at four concentrations on larvae and subsequent stages.
Among treated larvae, mortality percentages increased as the concentration of the assayed compound was increased, and also by treatment of earlier instar. Estimation of LC50 showed that flufenoxuron was more effective on S. littoralis than lufenuron by treatment of 2nd instar, and on A. ipsilon by treatment of larvae in their 2nd & 6th instars. Malformations were detected among treated larvae and the subsequent pupae and adults. Flufenoxuron was more effective in causing malformations among S. littoralis stages than lufenuron, while the vice versa occurred on A. ipsilon.
Larval treatments caused disturbances in the larval duration. Prolongations in the larval period were evident by treatment of the 4th instar larvae. Larval treatments of both insect species caused reductions in weights of the subsequent pupae. Also, shorter pupal periods among S. littoralis pupae resulted from treated larvae, while the effects on A. ipsilon pupal weights were, mostly insignificant.
Treatments of larvae by flufenoxuron and lufenuron resulted male & female moths of shorter longevity and reductions in the average number of deposited eggs/female, in addition to great reductions in the hatchability percentages than control. These effects were evident on the two insect species.