Biological Control not on Target

Non-target effects of exotic biological control agents, parasitoids and predators, released worldwide to control insect pests, are becoming more apparent. This paper summarizes previously recorded information on the diet breadth of natural enemies released to control insect pests worldwide. It also summarizes the diet breadth of native parasitic hymenoptera in North America to determine whether the diet breadths of native and exotic parasitoids differ. Of released biocontrol agents, 48% were recorded as generalists (attacking more than one genus of host) and another 29.2% attacked more than one species in a genus. Only 22.5% were recorded as specialists on the target pests. This suggests that many natural enemies released in biocontrol programs against insect pests have broad diets and that non-target effects are likely. Data from native hymenoptera in North America also show that many species attack multiple host genera and species, with an average of 5.8 genera and 7.3 species attacked, indicating broad agreement with data from biological control releases.