Natural enemy abundance and activity in a maize-leucaena agroforestry system in Kenya

The effect of maize-leucaena agroforestry system on the abundance and activ ity of natural enemies of maize stem borers was evaluated. The study covere d 6 cropping seasons from September 1992 to august 1995 and was conducted a t both Mtwapa and Amoyo in coastal and western Kenya, respectively. Treatme nts included monocropped and intercropped (maize [Zea mays], leucaena [Leuc aena leucocephala]) plots, weeded and unweeded, mulched and unmulched plots , and 3 spacing regimes (1.5, 2.25, 3.0 m) for leucaena hedgerows. Maize wa s interplanted at the onset of each rainy season. Rates of egg parasitism b y Trichogramma sp. and Telenomus sp, were not affected by intercropping, bu t decreased with increased hedgerow spacing. Significantly more egg batches were preyed upon in the maize monoculture plots. Parasitoids recovered inc luded the larval parasitiods Cotesia sesamiae (Cameron), Cotesia flavipes C ameron, Cotesia rufricus (Haliday), Glyptapanteles africanus (Cameron), Gon iozus indicus Ashmead, Chelonus curvimaculatus Cameron, unidentified Cotesi a sp. and Syzeuctus sp., the pupal parasitoid Pediobius furvus Gahan, and t he hyperparsitoid if Aphanogmus fijiensis (Ferriere). Larval and pupal para sitism at Mtwapa were unaffected by the vegetation structure or cultural tr eatment. However, at Amoyo, the percentage of stem borer larvae and pupae p arasitized were significantly greater in the maize monocrop plot than in th e intercropped plots, whereas parasitism also significantly increased with increasing hedgerow spacing. However, at both sites, larval and pupal morta lity were unaffected by the vegetation structure. The oviposition preferenc e of the predatory Chrysopa species was not influenced by the cropping syst em.