The potential of predators for pest control

Abstract

1. 1. Predators and biological control are defined and the distinction is stressed between ‘classical’ and ‘natural’ biological control. 2. 2. The characteristics of predators and predator-prey models are reviewed. Particular features considered are: voracity; area of discovery; functional response to prey density; mutual interference; reproductive and behavioural numerical response; spatial heterogeneity; and aggregative response of the predator. 3. 3. The role of these factors in promoting stability and reduction in prey numbers is briefly considered. It is concluded that a useful predator is voracious, continually feeding, with little handling time; it has an aggregative response to spatial patchiness of its prey, and can increase in numbers rapidly, often by immigration into the crop. 4. 4. The potential of predators is considered in: (a) cereals and field crops; (b) orchards and tree crops; and (c) glasshouse crops. 5. 5. It is concluded that there may be relatively few opportunities for the use of predators in ‘classical’ biological control, other than in glasshouses. There is, however, a need for the encouragement of naturally occurring, often polyphagous, predators in many outdoor crops. The role of such predators is still not fully appreciated. Pest management should safeguard these predators in order to realise their full potential for biological control.