Action of RH 5849, a non‐steroidal ecdysteroid mimic, on Plodia interpunctella (Hübner) in vivo and in vitro

Abstract

In memory of Christa L. Hoyt We have examined the effects of RH 5849, a lion-steroidal ecdysteroid mimic, on the growth and development of Plodia inferpuncteila. When R H 5849 was administered in the diet, larval growth was inhibited in a dose-dependent manner, while concentrations of 15 ppm and greater were highly toxic. However, the deleterious effects of RH 5849 could be prevented, except at very high concentrations of RH 5849, by the simultaneous administration of the juvenile hormone mimic methoprene. Larvae simultaneously treated with both hormone mimics continued to grow until they attained a size about three times normal. This growth was accompanied by at least one and sometimes two supernumerary molts, whereas, only an occasional supernumerary molt occurred in larvae treated with methoprene alone. In larvae undergoing supernumerary molts, wing imaginal discs produced a tanned pupal cuticle, but did not evaginate. When wing discs were cultured in vitro, RH 5849 stimulated evagination and chitin synthesis at concentrations of 10 and 1 pM, respectively. Likewise, RH 5849 stimulated GlcNAc uptake and inhibited cellular proliferation in IAL-PID2 cells at similar concentrations. These in vitro effects of RH 5849 also were produced by 20-hydroxyecdysone, but at lower concentrations. We conclude that RH 5849 exhibits molting hormone activity in vivo as well as in vitro. However, the toxicological effects in /? interpunctella result from action on feeding and growth, rather than molting. Thus, RH 5849 represents a new class of IGR, which will have impact on our understanding of endocrine regulation and open up new avenues for pest control.

Effect of RH-2485 on development, metamorphosis and synthesis of major proteins in female silkworm Bombyx mori

“…Acute toxicity effects like loss of balance, tremors and extrusion of haemolymph immediately after topical application were consistent with earlier observations made in Leptinotarsa decemlineata Say, 1824 and Epilachna arivestis Mulsant, 1850 (Aller & Ramsay 1988), Popillia japonica Newman, 1841 (Monthean & Potter 1992) and Harmonia axyridis Pallas, 1773 (Carton et al 2003). The observations on cessation of feeding were in good agreement with the findings of Wing et al (1988) in M. sexta, Silhacek et al (1990) in P. interpunctella, Darvas et al (1992) in S. littura, Smagghe & Degheele (1993) in S. exigua and S. exempta, Leonardi et al (1996) in B. mori, Retnakaran et al (1997) in C. fumiferana. Tremor and loss of balance could be due to blockage of K + channel in nerves and muscles in response to non-steroidal ecdysteroid agonist (Salgado 1992).…”

“…Cessation of feeding and precocious moulting in the larvae treated with RH-2485 were reported by Wing et al (1988) in Manduca sexta (L., 1763), Silhacek et al (1990) in Plodia interpunctella (Hübner, 1813), Darvas et al (1992) in Spodoptera littura (F., 1775), Smagghe & Degheele (1993) in Spodoptera exigua (Hübner, 1808) and Spodoptera exempta (Walker, 1858), Leondardi et al (1996) in Bombyx mori L., 1758, Retnakaran et al (1997) in Choristoneura fumiferana and Smagghe & Degheele (1994) in S. exigua. At low doses, suppression of weight gain after treatment with RH-5849 or tebufenozide was also reported by Oberlander et al (1995), Smagghe et al (1995Smagghe et al ( , 1997, Blackford & Dinan (1997a, b).…”

Non‐steroidal ecdysteroid agonists: Tools for the study of hormonal action

“…In cultures of wing imaginal discs obtained from last instar larvae of the Indian meal moth, P. interpunctella, RH-5849 stimulated incorporation of I4C-GlcNAc into chitin. In these experiments, 10-100 times as much RH-5849 as 20E was needed for effective stimulation of both chitin synthesis and evagination in vitro Silhacek et al, 1990). Maximum effectiveness was obtained in these experiments with a limited duration of treatment (24h), just as is required for 20E (Dutkowski and Oberlander, 1974).…”

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

“…These compounds mimic the biological function of the natural insect molting hormone 20HE, inducing a premature and lethal larval molt by binding directly to the ecdysteroid receptors (Dhadialla et al 1998, Smagghe et al 2004. Ecdysone agonists are highly selective against lepidopteran larvae, with the result that other insects are often less affected by them (Silhacek et al 1990, Schneider et al 2003. In addition, their narrow spectrum of activity, positive ecotoxicological pro ile, and short persistence in the environment makes these compounds promising against many economically important agriculture and forest pests (Sundaram et al 2002, Biddinger et al 2006, Osorio et al 2008.…”