Effects of anti-juvenile hormone agents and a juvenile hormone analog on neck-ligated post-feeding last instar larvae of Spodoptera mauritia Boisd. (Lepidoptera:Noctuidae)

Abstract

The ability of three anti-juvenile hormone agents (AJHAs) to prevent the juvenile hormone dependent phase of larval-pupal transformation has been investigated. Neck-ligated post-feeding last instar larvae of Spodoptera mauritia were treated topically with different doses of a juvenile hormone analog (JHA) or the AJHAs, tetra-hydro-4-fluoromethyl-4-hydroxy-2H-pyran-2-one (FMev), ethyl-4-[2-(tert-butyl carbonyloxy)butoxy] benzoate (ETB) and ethyl-[E]-3-methyl-2-dodecanoate (EMD). Untreated ligated larvae or those treated with acetone survived for 12 ± 1 days without showing any sign of pupal cuticle secretion. On the other hand treatments of ligated larvae with different doses of JHA induced pupation. Among the three AJHAs tested treatments of ETB promoted pupation. Treatments of ligated larvae with lower doses of EMD induced the formation of larval-pupal intermediates whereas those treated with higher dose moulted into either pupae or larval-pupal intermediates. FMev-treated larvae exhibited a complete inhibition of moulting and metamorphosis. In order to study whether AJHAs would prevent the JHA induced pupation, neck-ligated larvae were treated simultaneously with different doses of AJHAs and 1μg JHA. Co-application of JHA with different doses of EMD induced pupation in majority of the ligated larvae and thus appears to a certain extent to counteract the effects of treatments of same doses of EMD alone. Co-application of JHA with different doses of ETB elicited pupation in all the surviving ligated larvae. To a large extent co-application of JHA with different doses of FMev failed to induce pupation. The significance of the findings is discussed in the context of the mode of action of these AJHAs. Les trois (AJHAs) ont ete examines son pouvoir qu’ empeche la transformation du Juvenile hormone dependent phase de larvaere-pupae. Ayant nourir derniere stade cou-ligatures larvaire de Spodoptera mauritia sont traite topicalement avec en doses differements du Juvenile hormone analog (JHA) ou AJHAs, tetra-hydro-4-fluoromethyl-4-hydroxy-2H-pyran-2-one (FMev), ethyl-4-[2-(tert-butyl carbonyloxy)butoxy] benzoate (ETB) et ethyl-[E]-3-methyl 2-dodecanoate (EMD). Non traite larvaire ligatures ou celles sont traite avec acetone survie pendant 12 ± 1 jours sans aucune signe de secretion par pupal cuticle. D’ailleurs traitement des larvaires ligatures avec en doses differents de JHA induit pupation. Parmi les larvaire deja traite par trois AJHAs sont induit pupation par ETB. Traitment des larvaires ligatures avec en doses inferieurs du EMD induit la formation de larvaires-pupal intermediares tandisque celles qui sont traites en doses superieurs mue a pupae ou larvaires pupal intermediares. Larvaires traites par FMev montre une inhibition complete du mue et metamorphosis. A fin d’etudier si AJHAs empechevont JHA induit pupation, cou-ligature larvaires sont traite simultanement avec en doses differents des AJHAs et 1μg JHA. En majorite des larvaires ligatures induit pupation par co-traitment de JHA avec en doses differents de EMD. Co-traitment de JHA avec en doses differents de ETB elicit pupation dans toutes les larvaires ligatures survivant. En plus part des cas co-traitment de JHA avec en doses differents de FMev n’induit pas la pupation. Les significances des resultats ont discutes d’une manniere de la mode d’action des AJHAs.