Predicting Natural-enemy Responses to Herbivores in Natural and Managed Systems

One underutilized approach for bridging the gap between basic research on plant–insect–enemy interactions and applied research on biological control is to examine prey defensive characteristics as predictors of successful pest eradication by specific natural enemies. We used such a prey-based approach to compare predictors of predator and parasitoid response in natural systems to predictors of success of biological control. To construct predictive models based on defensive characteristics, we used data from predation (34 prey species) and parasitism (98 host species) studies on lepidopteran larvae in natural systems. To compare efficacies of defenses in natural vs. biocontrol systems and to test the predictions from natural systems, we examined data from 150 biological control programs that used predators and parasitoids as control agents. Predictors were different for each type of natural enemy, yet the patterns of association were similar in natural and biocontrol systems. Specialists and gregarious larvae had high levels of parasitism in natural systems and were successfully controlled by biocontrol programs using parasitoids. Cryptic and smooth larvae had high levels of predation in natural systems and were successfully controlled by predators in biological control programs. Predictions derived from the naturalsystem models explained 53% of the variation in success of biocontrol efforts.