Beyond Pandora's Box: quantitatively evaluating non-target effects of parasitoids in classical biological control

A seminal paper by Howarth (Proc Hawaii Entomol Soc 24:239-244, 1983) entitled Classical biological control: Panacea or Pandora's Box ignited a sometimes acrimonious debate over the relative safety of introductions for classical biological control. Extolled for years as environmentally benign, the litany of negative non-target effects profiled by Howarth heightened awareness of this issue. Several factors have muddied this debate including the conflation of frequency of effects with their strength, grouping the effects of disparate biological control agents together, and the lack of quantitative data on either side of the argument. Here, I examine the potential for non-target effects among insect parasitoids, the most common group used for biological control of arthropods. In response to calls for better quantitative studies, I highlight three different techniques, quantitative food webs, life table analysis, and experimental populations, respectively, to quantitatively assess or reassess non-target effects in different systems. I also explore three methodological approaches employed to ascertain the strength of competitive interactions between native and introduced parasitoids, a potential non-target effect that has received little attention in the literature. These types of studies may greatly increase our understanding of the nature of non-target interactions with introduced parasitoids and bring more rigor to a debate often dominated by rhetoric.