Host plant cultivar of the grapevine moth Lobesia botrana affects the life history traits of an egg parasitoid

The quality and susceptibility of insect eggs for egg parasitoids may be affected by the diet experienced by the females that produce the host eggs. We tested the hypothesis that the host plant fed upon by an herbivore during the larval stages will determine the quality of the eggs laid by the adult for an egg parasitoid. We used the tritrophic system comprising five grape cultivars, the European grapevine moth, Lobesia botrana and the parasitoid Trichogramma evanescens. Parasitoid performance in host eggs of different sizes and originating from five grape cultivars was determined. Overall, egg parasitism was higher on cultivars on which L. botrana laid larger eggs, which resulted in higher larval survival and faster development time of the wasps. One exception was found for the cultivar Pinot. Trichogramma wasps parasitized fewer eggs originating from females that fed on the Pinot cultivar as larvae despite good progeny performance (high survival and fast development time). The poor motivation of the parasitoid to oviposit in “Pinot” eggs could be a result of deterrence due to plant compounds ingested by the moth as a larva and transferred to the eggs, or lack of plant-derived compounds that stimulate oviposition in the parasitoid. Interestingly, within a cultivar, Trichogramma larval survivorship was higher in younger, smaller eggs than in older, larger ones. This effect however is confounded by the effect of the plant cultivar, since the host egg size varies among grape varieties. Overall, the results of this study support the hypothesis that an herbivore’s host plant can influence the performance of its egg parasitoids.