Effects of nonsteroidal ecdysone agonist RH-5992 and chitin biosynthesis inhibitor lufenuron on Spodoptera littoralis (Boisduval, 1833)

Comparative studies of the effects of two compounds, tebufenozide (an ecdysone agonist) and lufenuron (an insect growth regulator inhibiting chitin synthesis), were conducted on Spodoptera littoralis (Boisduval, 1833). The compounds, orally administered, caused larval mortality proportional to the concentrations in the food source. Tebufenozide initiated precocious molting, and lufenuron, and inhibited chitin synthesis. In both cases, larvae were unable to complete the molting process and died in the old larval cuticle. Larvae contaminated by sublethal doses completed their development to adulthood. Lufenuron is more active than is tebufenozide. LD-50 for lufenuron is 0.0001ppm and for tebufenozide 0.001ppm. Topical application of the test compounds to eggs caused dose- and agedependent inhibition of embryonic development. Application of tebufenozide in the second half of embryogenesis caused precocious molting of eclosed larvae of the 1st instar. Some morphological changes in the process of larval-pupal transformation were also observed. Tested compounds also reduced reproduction in adult individuals that had been treated by the tested compounds in the larval stage.

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