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

Classical biological control is often considered a cornerstone of integrated pest management, although the introduction of exotic natural enemies can have unpredictable and wideranging impacts on native ecosystems. In this article, I question the wisdom of using the classical approach as an automatic Þrst 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 speciÞc 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 Þeld, while predation is less apparent and far more difÞcult 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 Ôrear and releaseÕ 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 reßexive 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 programmay be embarked on regardless ofwhether or not suitable candidate species for introduction can be identiÞed, 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.