Classical Biological Control: A Critical Review of Recent Programs Against Citrus Pests in Florida

Abstract

Classical biological control is often considered a cornerstone of integrated pest management, although the introduction of exotic natural enemies can have unpredictable and wide-ranging impacts on native ecosystems. In this article, I question the wisdom of using the classical approach as an automatic first response to invasive pests. I critically evaluate some classical biological control programs recently implemented against invasive pests of citrus in Florida including: Lysiphlebia japonica Ashmead and Lipolexis scutellaris Mackauer (Hymenoptera: Aphidiidae) introduced against the brown citrus aphid, Ageniaspis citricola Logviniskaya (Hymenoptera: Encyrtidae) against the citrus leafminer, and Tamarixia radiata (Waterston) (Hymenoptera: Eulophidae) against the Asian citrus psyllid. I advance the following contentions: (1) Not all invasive pests are appropriate targets for the classical approach, especially those that lack natural enemies specific to, or effective against them. (2) Some invasive pests may be effectively controlled by generalist predators within a time frame similar to that required for evaluation of introduced parasitoids. (3) The contributions of native species are often ignored when postrelease evaluations focus on introduced species. (4) Parasitism is a highly apparent phenomenon in the field, while predation is less apparent and far more difficult to quantify, an empirical disparity that may generate an undue bias regarding the perceived importance of introduced parasites relative to indigenous predators in biological control. (5) Classical programs have immediate political appeal to agricultural sectors seeking quick solutions to new pest problems, and to the government agencies seeking to respond to their demands for action. Thus, funding incentives for research may be biased toward ‘rear and release’ classical programs and away from other, ecologically sound approaches to pest management such as conservation biological control. I conclude that classical programs are typically employed as a reflexive response to invasive pests, often without adequate evaluation of the pest as a potential, rather than automatic, target for this approach, and without prerelease surveys to document indigneous natural enemies. A classical program may be embarked on regardless of whether or not suitable candidate species for introduction can be identified, and often without objective postrelease evaluations. The net result is a prevailing tendency to underestimate the potential ecological resiliency of established insect communities to invasive pests.