How to assess non-target effects of polyphagous biological control agents: Trichogramma brassicae as a case study.

We show key elements of the risk assessment conducted for Trichogramma brassicae Bezdenko (Hymenoptera: Trichogrammatidae), an egg parasitoid which is successfully used for control of the European corn borer in European countries. The main factors that we addressed in this study were: the potential of establishment; acceptance and parasitism of non-target butterflies under laboratory, field-cage and field conditions; the searching efficiency in non-target habitats; the dispersal capacities; and the potential for effects on other natural enemies in maize. Although high parasitism of non-target butterflies and other natural enemies were observed under laboratory conditions, very few eggs of the non-target species were attacked in the field. These findings may be explained by a low host searching efficiency and the observation that female T. brassicae do disperse only a few meters per day. We conclude that the possibility of using invertebrate agents with a broad host range in inundative biological control should not a priori be excluded, however, a thorough environmental risk assessment should be performed prior to release.