The modified configuration of a field resulting from integration of trees with crops, or vice versa, may affect colonization of the plants by insect pests. The masking effect of odours released by different plant species in polycultural systems such as those of agroforestry interfere with insects' orientation abilities. Trees raised with crops in agroforestry fields act as physical barriers to the movement of insects to, from and within the field. A barrier effect can also result from the presence of non-host plants among the host plants. Agroforestry practices favour the establishment of natural enemies of insect pests.
Caution is recommended when introducing exotic plants into agroforestry systems.
Little information is available about insect pests in different agroforestry systems. The effect of interactions among components on the insect pests needs to be studied. The insect-pest situation in agroforestry is reviewed. Studies on insect pests in ongoing agroforestry trials in Africa are discussed and future directions for research suggested.