Biological control of fruit flies in Hawaii: Factors affecting non-target risk analysis

Abstract

The potential negative impacts of biological pest control on non-target species have become the focus of a contentious debate. In this article, we use examples from both classical and augmentative biological control of fruit fly pests in Hawaii to address several important factors in assessing non-target risks of fruit fly parasitoids. Several fruit fly parasitoids have been introduced to Hawaii and contribute substantially to the reduction of pest populations in the state's farms and forests. However, an historical lack of host-specificity testing of these parasitoids with non-target species has raised concerns about their impact on non-pest fruit flies, including some flies deliberately introduced for biological control of weeds and others that are endemic Hawaiian species. When developing protocols to assess risks of introduced fruit fly parasitoids, we need first to define an appropriate range of species against which host specificity should be tested. For assessing susceptibility of a non-target species to parasitoids, behavioral tests are as important as suitability tests. Experimental factors, such as host-exposure substrate, absence or presence of preferred hosts, and laboratory vs. natural conditions, are shown to affect the results of host-specificity tests and risk analysis. Still, assessing long-term, indirect ecological impacts of parasitoids and weighing potential risks and benefits in multiple dimensions (besides dollar values) remains a challenge to environmentalists, conservationists, applied ecologists, and biocontrol practitioners.