Lessons from history: predicting successes and risks of intentional introductions for arthropod biological control

The introduction of normative biological control agents into a new region is one of the several approaches to managing the deleterious effects of normative invasive species. Predicting outcomes of such introductions has proven difficult. The US National Invasive Species Management Plan (2001) calls for better screening methods for intentional introductions, including normative biological control agents for animal pests. To address this challenge, I searched current and historical literature to develop a database of 13 life history traits and 8 descriptive variables for 87 normative insect biological control species in the continental United States. Models for predicting success in controlling a target species and likelihood of nontarget effects (documented cases of attacks on native hosts, prey, or natural enemies) were developed using logistic regression. The most important life history traits for predicting success included host specificity, whether the agent was a predator or parasitoid, and number of generations per year. There was no information about nontarget effects in 50 of 87 cases. Traits important for predicting nontarget effects included sex ratio of progeny and the documented presence of native natural enemies. This quantitative approach, derived from a meta-analysis of historical data, can be useful in developing guidelines for intentional introductions and predicting ecological outcomes of a broader range of nonnative species in new environments.