A critical evaluation of augmentative biological control

Published source details Collier T. & Van Steenwyk R. (2004) A critical evaluation of augmentative biological control. Biological Control, 31, 245-256.
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Summary

Augmentative biological control (the release of large numbers of captive-reared natural predators to augment natural predator populations, or inundating pest populations with natural predators) is applied in relatively few agricultural systems, despite the potential to control arthropod crop pests, thus avoid or reducing the need for pesticide application.

A literature review was undertaken to assess the efficacy of augmentative biological in terms of effectiveness in suppressing agricultural pests, cost effectiveness and ecological factors limiting success. Over 140 studies of augmentative biological control were identified and reviewed.

Effectiveness was evaluated by assessing whether pest densities were suppressed to specified target levels and by reviewing studies that compared augmentation with pesticide application.

Pest populations were suppressed below target densities through augmentation in only five out of 31 (16%) of the natural predator–pest cases reviewed, and failed 64% of the time. It was also usually the case, though not always, that augmentation was less effective than pesticide application in controlling pests.

Cost-wise, augmentative releases were often more expensive than pesticides, although there were cases where augmentation was cost effective. More cost-benefit types of analysis of augmentation are needed to give a more informed picture. Unfavourable environmental conditions for release of captive-bred predators, predator dispersal upon release, compensatory mortality, pest refuges free of predators, and predation upon the released bioagents themselves, were most often implicated as ecological factors limiting augmentation efficacy. Combining different natural pest predator species and/or by combining augmentative releases with low-risk pesticides might increase efficacy although more research is required to provide evidence for this.

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