Opportunities for biological control of insect pests in tropical Africa.
Although biological control introductions have been made into Africa since 1928, only 15 insect pests have been controlled in 9 countries. The different ways in which natural enemies can be applied are outlined, and criteria for selecting appropriate controls and their constraints are discussed in relation to ecological theory. Pest life-history, strategy, crop type, stability of the agroecosystem and the effects of crop improvement are shown to provide guidelines on the choice of biological control technique. The economic benefits of using classical biological control are emphasized, using examples for which cost and benefit calculations have been made. With this background, opportunities for applying biological control are outlined. It is concluded that classical biological control should be the preferred technique, when appropriate, and that programmes should be thoroughly researched to enhance the probability of success.