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)

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 5 th (penultimate) instar and 6 th (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 6 th instar larvae with PI. With regard to the adult longevity, the major effect of PI was the promotion of adult females to live longer lifetime. Both preoviposition and oviposition periods had been slightly, or considerably, shortened. After topical application of PI onto 5 th instar larvae, the oviposition rate was drastically regressed only at the lower two doses. After treatment of 6 th 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 5 th instar larvae with PI but complete sterility had been recorded after treatment of 6 th instar larvae only with 150 and 30 µg/larva. The incubation period was remarkably prolonged.

Physiological Activities of Anti-Juvenile Hormone Agents Against Insects and Their Role For Devising Fourth Generation Insecticides: A Comprehensive Review

“…Five sublethal doses of PI had been topically applied (once) onto 1-day old larvae of 5 th or 6 th (last) larval instar of S. littoralis. PI exhibited a slightly extended toxic effect on the adult females only with the higher two doses (Ghoneim and Bosly, 2017).…”

“…After topical application of PI onto 5 th instar larvae of S. littoralis, the oviposition rate was drastically regressed only at the lower two doses. After treatment of 6 th instar larvae with PI, the oviposition rate was remarkably depressed in a dose-dependent course (Ghoneim and Bosly, 2017). The prohibited oviposition efficiency may be explained as a result of the inhibition of ovarian DNA synthesis or the interference of IGRs or anti-JH compounds with vitellogenesis via certain biochemical processes.…”

“…Adult malformations were observed in P. dux after topical application of PII onto the 3 rd instar larvae (Nassar et al, 1999); P. ricini after topical application of PII onto larvae (Khan and Kumar, 2000); S. ruficornis after topical application of PII onto larvae (Khan and Kumar, 2005); C. megacephala after topical application of PII onto the early and late 3 rd instar larvae (Singh and Kumar, 2011); S. littoralis after larval treatment of with PI and PII (Khafagi and Hegazi, 1999); L. decemlineata after topical application of PІ and PIІ onto 2 nd instar larvae (Farazmand and Chaika, 2008); M. domestica after treatment of larvae with PIІ (Gaur and Kumar, 2009) and S. gregaria after injection of a single dose (50 or 150 µg) of PII into the 4-day old adults (Tawfik et al, 2014). Recently, Ghoneim and Bosly (2017) topically applied five sublethal doses of PI onto 1-day old larvae of 5 th and 6 th (last) larval instars of S.…”

“…Longevity of the parasitoid adult females was shortened. In a study conducted by Ghoneim and Bosly (2017), five sublethal doses of PI had been topically applied onto 1-day old larvae of 5 th or 6 th (last) larval instars of S. littoralis. The emerged adult females spent longer longevity than their control congeners.…”

“…After treatment of E. integriceps nymphs with PI, fecundity of adult females was reduced (Amiri et al, 2010). According to Ghoneim and Bosly (2017), sublethal doses of PI had been topically applied onto 1day old larvae of 5 th or 6 th (last) larval instars of S. littoralis. The fecundity of adult females was dramatically reduced.…”