Behaviour of Trichogramma brassicae Bezdenko (Hym.: Trichogrammatidae) towards Lobesia botrana Denis & Schiffermuller (Lep.: Tortricidae).

The microhymenoptera Trichogramma brassicae Bezdenko is used in biological control of the European com borer, Ostrinia nubilalis Hubner. Kairomone sub stances emitted by this Lepidoptera influence the search behaviour of the p arasitoid. The feasibility of using T, brassicae against another economical ly important pest, the European grapevine moth, Lobesia botrana Denis ge Sc hiffermuller little parasitized by this oophagous insect. The study focused mainly on the allelochemical relations between these two insects. Our aims were i) determining why L. botratia is little parasitized by T. brassicae ii) identifying the kairomones which could be used to manipulate so as to o ptimize its effectiveness against this phytophagous insect. In this paper, previously, we have shown that just before oviposition L. botrana did not d eposit a trail which assist T. brassicae to find the host. We quantify the long and/or short range effects of L. botrana females and eggs on the behav iour of T. brassicae. Only calling females caused a slight increase in para sitoid movement and significantly increased the number of females which par asitize. The effect of eggs distribution on host location and oviposition b ehaviour was examined in the presence of either isolated eggs or grouped eg gs of L. botrana. T brassicae females found isolated eggs more rapidly. How ever, once they found the grouped eggs, they parasitized them more rapidly. Isolated eggs were not a drawback as far as time was concerned under our c onditions. Compared to O. nubilalis, the substances emanating from L. botra na had little effect on the behaviour of the parasitoid and on its potentia l for parasitism. In relation with our results, at present, T. brassicae is unlikely to be useful against L. botrana.