Effects of ecdysteroid agonist RH‐2485 reveal interactions between ecdysteroids and juvenile hormones in the development of Sesamia nonagrioides

Abstract

Larvae of Sesamia nonagrioides developing under long day (LD) conditions pupate in the 5th or 6th instar, whereas under the short day (SD) conditions, they undergo several supernumerary larval molts and are regarded as diapausing. The development in early larval instars occurs in the LD larvae at a moderate and in the SD larvae at a high juvenile hormone (JH) titer; ecdysteroid titer cycles similarly under both conditions. The transformation to pupa is initiated by a burst of ecdysteroids at undetectable JH levels, whereas extra larval molts in the diapausing larvae are associated with moderate JH titer and irregular rises of ecdysteroids. Application of 0.2 ppm RH-2485 to the diet of the 6th instar larvae promotes hormonal changes supporting metamorphosis in the LD larvae and slightly accelerates larval molts in the diapausing SD larvae. The 0.5- and 1-ppm doses revert these patterns of endocrine regulations to a mode typical for early larval instars. Particularly dramatic is a JH titer increase provoked within 24 h in the LD larvae. After the treatment, both the LD and SD larvae undergo a series of larval molts, suggesting that hormonal programming of the larval development has been stabilized. A few insects receiving 1 ppm RH-2485, and a high proportion of those fed with 5 ppm RH-2485, deposit two cuticles within a single apolysis and die.

Lethal and Sublethal Effects of Methoxyfenozide on the Development, Survival and Reproduction of the Fall Armyworm, Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae)

“…Thus, the insects molted to nonviable forms between the life stages (Tateishi et al 1993). Molts induced during the early phase of the last instar produce larval-like individuals, while those formed in the late phase generate pupal-like individuals (Eizaguirre et al 2007), as was observed in our study.…”

“…It is documented that ecdysone agonists cause larvae to stop feeding, what leads to a reduced larval body weight (Pineda et al 2006, Eizaguirre et al 2007. In our study, the effect of methoxyfenozide on pupal weight was dose-dependent and more pronounced in females than in males.…”

“…These effects include delayed or accelerated developmental time (Adel & Sehnal 2000, Biddinger et al 2006, weight loss of both larvae and pupae (Pineda et al 2007, Zamora et al 2008, mortality and pupae deformations (Gobbi et al 2000, Pineda et al 2004, wing deformities in adults (Trisyono & Chippendale 1998, Sundaram et al 2002, disturbed diapause (Eizaguirre et al 2007), impaired reproductive parameters (Seth et al 2004, Smagghe et al 2004, and changes in the adult sex ratio (Biddinger et al 2006). In addition, Hoelscher & Barret (2003) reported that methoxyfenozide interfered with the ability of Argyrotaenia velutinana (Walker) and Choristoneura rosaceana (Harris) (Lepidoptera: Tortricidae) adult males to respond to the pheromones of sexually mature females.…”

Expression of the Hsp83 gene in response to diapause and thermal stress in the moth Sesamia nonagrioides

“…The ecdysteroids titer rose before each extra larval moult in S. nonagrioides and a burst at the passing 8 th to 9 th instar (Eizaguirre et al. , 2007) that is at day 60 of our collection time (Fantinou et al.…”

Foliar persistence and residual activity of methoxyfenozide against beet armyworm (Lepidoptera: Noctuidae)

“…The high effectiveness of methoxyfenozide against lepidopteran larvae when exposed, either through topical application or by ingestion, has been widely recognized (Pineda et al ., ; Eizaguirre et al ., ; Rodríguez et al ., ). One of the reasons for the efficacy of ecdysone agonists is their rather high foliar stability.…”