Disruptive Impact of Precocene I (juvenile hormone-antagonist) on the Adult Performance and Reproductive Potential of the Egyptian Cotton Leafworm Spodoptera littoralis Boisduval (Lepidoptera: Noctuidae)

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1 1Faculty of Science, Al-Azhar University, Cairo, Egypt

2 Department of Biology, Faculty of Science, Jazan University, Jazan, Saudi Arabia

Abstract

The cotton leafworm, Spodoptera littoralis is destructive pest of cotton and various crops all over the year. The present study was carried out aiming to assess the effects of Precocene I (PI) on the most important parameters of adult performance and reproductive potential of this pest. Five sublethal doses: 150, 120, 90, 30 and 15 µg/larva had been topically applied (once) onto 1-day old larvae of 5th (penultimate) instar and 6th (last) instar. The adult emergence was slightly, or drastically, blocked, depending on the dose level and larval instar under treatment. PI exhibited a slightly extended toxic effect on the adult females only with the higher two doses. Some adult deformities were produced after treatment of 6th instar larvae with PI. With regard to the adult longevity, the major effect of PI was the promotion of adult females to live longer life-time. Both pre-oviposition and oviposition periods had been slightly, or considerably, shortened. After topical application of PI onto 5th instar larvae, the oviposition rate was drastically regressed only at the lower two doses. After treatment of 6th instar larvae with PI, the oviposition rate was drastically regressed in a dose-dependent course. Both fecundity and fertility were dramatically reduced. Complete sterility was recorded after treatment of 5th instar larvae with PI but complete sterility had been recorded after treatment of 6th instar larvae only with 150 and 30 µg/larva. The incubation period was remarkably prolonged.

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