Utilization of natural enemies of Chilo spp. for management in Africa.
Knowledge of the natural enemies of graminaceous stem borers is outlined, with special reference to mortality of Chilo spp. as crop pests in Africa. The scanty quantitative information available suggests that over 90% mortality of eggs and larvae takes place before the larvae become established as borers in the crop and that mortality of the older larvae and pupae is much lower. Possible manipulations of natural enemies to increase mortality further are reviewed. In view of the largely negative results of past classical biological control introductions, the prospects do not appear very promising. The results, however, do indicate some possibilities which should be investigated, notably trials with Apanteles spp. (Braconidae) and intra-continental redistribution of important species with restricted distributions. For short-term biological control, development of microbial biopesticides seems a more promising strategy than augmentation of insect parasitoids by breeding and release, particularly on small farms. A 3rd possibility, enhancement of the action of native natural enemies by environmental manipulation, merits more attention as part of an integrated crop production approach to the improvement of the quantity and reliability of yields for the small farmer.