Laboratory rearing and biological parameters of the eulophid Pnigalio agraules, a parasitoid of Cameraria ohridella.

Predators as well as parasitoids native to Europe accept the exotic horse chestnut leafminer, Cameraria ohridellaDeschka and Dimic 1986 (Lepidoptera: Gracillariidae), either as prey or as host. However, the influence of these antagonists on the populations of the pest insect is so far very low. Therefore, efforts to develop an integrated pest management system against C. ohridella should include methods which foster the natural enemy complex. In the present study we developed a laboratory rearing method and investigated several biological parameters of Pnigalio agraules (Walker 1839) (Hymenoptera: Eulophidae), a dominant species in the horse chestnut leafminer’s parasitoid complex in many European regions. This native parasitoid satisfies three basic requirements for successful use as a biocontrol agent with regard to C. ohridella. The parasitoid’s fecundity, longevity and the speed of juvenile development by far exceeds that of the leafminer, enabling the parasitoid population to increase faster than that of the host. Furthermore, our results show that the impact of this species on C. ohridella populations has been previously underestimated, because non-reproductive killing (i.e. host-feeding and host-stinging) of the hosts, resulting in considerable larval mortality of the leafminer, has not been quantitatively assessed. However, naturally occurring parasitoid populations have negligible impact on C. ohridella populations. Further studies, including experimental releases of P. agraules, are necessary to understand the constraints limiting the parasitoid’s performance in the field and to assess the potential benefits of releases for the control of C. ohridella.