ABSTRACT

Biological control can be defined as the control of pests or pathogens by other organisms. The introduction of a biocontrol agent is aimed at reducing the population of the pest or pathogen to below an economic damage threshold for that particular crop. But biological interactions occur naturally, and it is through the effects of these that plant and animal populations are regulated and generally kept in balance (Figure 6.1). Our agricultural practices that produce vast monocrop areas distort this balance in favor of the crop plant, which may increase the attack by host-specific herbivores and disease (Figure 6.2). The introduction of biocontrol agents is used to reduce the seriousness of these attacks and maintain a plant population at a higher density than would occur in the wild. Biocontrol is an exercise in population management and with it goes the responsibility of understanding the possible effects on nontarget populations. In this chapter some of these interactions are

considered and the possible mechanisms of biocontrol discussed.