La spécificité deDiadromus pulchellus [Hyménoptère: Ichneumonidae] vis-à-vis de son hôteAcrolepiopsis assectella, la teigne du poireau

Microorganisms are involved in the production of volatile kairomones affecting the host seeking behaviour of Diadromus pulchellus, a parasitoid of Acrolepiopsis assectella

“…They are larger than those of A.assectella, their cuticle is harder and their cocoons are denser, with no openings at the extremities preventing D.pulchellus females from reaching the Cpronubana chrysalids with their ovipositor, in the same way that the cocoons would prevent parasitism on Ephestia kuehniella or Plodia interpunctella (Thibout, 1988). Finally it is not certain that the cocoons of Cpronubana and their nymphal cuticle contain kairomones required for host recognition, in contrast to A.assectella (Bekkaoui & Thibout, in preparation).…”

Rôle de substances cuticulaires non volatiles d'Acrolepiopsis assectella (Lep.: Hyponomeutoidea) dans la reconnaissance de l'hôte par les parasitoïdesDiadromus pulchellus etD. collaris (Hym.: Ichneumonidae)

“…Inversement, si D. pulchellus peut parasiter P. xylostella en laboratoire (Thibout, 1988), son seul h6te naturel connu est A. assectella.…”

“…L'entomophage localise la plante hrte A l'aide de substances volatiles soufrres 6mises par le poireau, particulirrement quand il est attaqu6 par les larves de la teigne (Leeomte & Thibout, 1986), substances 6galement retrouvres dans les frcrs des larves hrtes (Auger et aL, 1990). Quand le parasito'ide arrive au contact de l'hrte, un deuxirme type de stimulus est utilisr, stimulus de contact de nature encore inconnue, lirs au cocon et la cuticule de la chrysalide-h6te (Thibout, 1988 ;Thibout et aL, 1988). Dans ce premier travail, seuls les effets des kairomones cuticulaires de la chrysalide permettant la reconnaissance de l'h6te ont 6t6 6tudirs sur le comportement de D. pulchellus et d'une esprce sympatrique, D. collaris parfois observre sur le mrme phytophage (Fredlaai, 1957).…”

Evaluation of a candidate classical biological control agent and critical assessment of suggested host specificity testing guidelines

“…While the sulphur-dominated chemical profile is a classic characteristic of Allium spp., it is also a trademark of the Brassicaceae (Bailey et ah, 1961), which contains many cultivated and weedy species common in "North America. Furthermore, Lecomte and Thibout (1984) showed that D. pulchellus is stimulated by volatile sulphur compounds from brassicaceous plants and Thibout (1988) has already demonstrated that the parasitoids can develop in Plutella xylostella (Linnaeus) (Lepidoptera: Plutellidae), which feeds on several Brassica species.…”

“…Although the phylogenetic relationships within Yponomeutoidea are not well understood, those species within the family Plutellidae appear to be closely related taxonomically to the acrolepiids (Dugdale et ah, 1998). Based on earlier indications that D. pulchellus was fairly host specific (Thibout, 1988), all non-targets outside of Yponomeutoidea were considered phylogenetic outgroups and therefore much less likely to be suitable for parasitoid development.…”