Non-target effects of insect biocontrol agents and trends in host specificity since 1985.
2016
Driesche, R. van | Hoddle, M.
Non-target impacts of parasitoids and predaceous arthropods used for classical biological control of invasive insects include five types of impact: (1) direct attacks on native insects; (2) negative foodweb effects, such as competition for prey, apparent competition, or displacement of native species; (3) positive foodweb effects that benefited non-target species; (4) hybridization of native species with introduced natural enemies; and (5) attacks on introduced weed biocontrol agents. Examples are presented and the commonness of effects discussed. For the most recent three decades (1985-2015), analysis of literature on the host range information for 158 species of parasitoids introduced in this period showed a shift in the third decade (2005-2015) towards a preponderance of agents with an index of genus-level (60%) or species-level (8%) specificity (with only 12% being assigned a family-level or above index of specificity) compared with the first and second decades, when 50 and 40% of introductions had family level or above categorizations of specificity and only 21-27 (1985-1994 and 1995-2004, respectively) with genus or 1-11% (1985-1994 and 1995-2004, respectively) with species-level specificity. In all three decades, 11-12% of introductions could not be classified in this manner due to lack of information. Recommendations for future actions to improve this record are made: (1) distinguish host use from population-level impact; (2) develop country-level online summaries of relevant information; (3) plan biological control projects with conservation partners; and (4) conduct post-release comparisons of actual impact to predicted risk based on quarantine studies.
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