The case for insect pest management in agroforestry research

Abstract

Insect pest problems in agroforestry are likely to arise from two sources: those problems associated with the importation of wild plants into intensively managed ecosystems and those related to some peculiar features of agroforestry. These problems become more prominent if the imported woody plants are taxonomically related to the food or commercial crops of a recipient country. In this paper, the insect pest complex of the leguminous genus Acacia, with emphasis on Acacia mollissima (=mearnsii), is briefly reviewed to illustrate the potential insect pest problems to the exotic plants themselves and how, as companion crops, the exotic plants may compound the pest problems of food legume crops. There is presently a contention that agricultural insect pest management strategies are duplicatable in agroforestry systems. But the bio-ecological factors governing the population dynamics of the insect pests in the two systems are not necessarily the same. This is largely because agroforestry, with time, matures into a complex system of perennial woody plants whose ecology is temporarily interrupted by the cultural processes of crop husbandry and harvesting of these annual crops, while the modern, herbaceous-agricultural systems remain perpetually youthful as ripened crops are harvested and the unwanted vegetative parts ploughed down or removed off the fields. Because of this, the author has suggested that new sets of data are required for insect pest management in agroforestry systems. Data on insect pest behaviour as influenced by (i) plant species diversity, (ii) perennial woody plants, (iii) age of the agroforestry system and (iv) the cropping pattern and relatedness of the companion crops, are considered paramount at this stage of agroforestry science.