Natural Enemy Abundance and Activity in a Maize-Leucaena Agroforestry System in Kenya

Abstract

The effect of maize-leucaena agroforestry system on the abundance and activity of natural enemies of maize stem borers was evaluated. The study covered 6 cropping seasons from September 1992 to August 1995 and was conducted at both Mtwapa and Amoyo in coastal and western Kenya, respectively. Treatments included monocropped and intercropped (maize [ Zea mays ], leucaena [ Lencaena leucocephala ]) plots, weeded and unweeded, mulched and unmulched plots, and 3 spacing regimes (1.5, 2.25, 3.0 m) for leucaena hedgerows. Maize was interplanted at the onset of each rainy season. Rates of egg parasitism by Trichogramma sp. and Telenomus sp. were not affected by intercropping, but decreased with increased hedgerow spacing. Significantly more egg batches were preyed upon in the maize monoculture plots. Parasitoids recovered included the larval parasitiods Cotesia sesamiae (Cameron), Cotesia flavipes Cameron, Cotesia rufricus (Haliday), Glyptapanteles africanus (Cameron), Goniozus indicus Ashmead, Chelonus curvimaculatus Cameron, unidentified Cotesia sp. and Syzeuctus sp., the pupal parasitoid Pediobius furous Gahan, and the hyperparsitoid Aphanogmus fijiensis (Ferriere). Larval and pupal parasitism at Mtwapa were unaffected by the vegetation structure or cultural treatment. However, at Amoyo, the percentage of stem borer larvae and pupae parasitized were significantly greater in the maize monocrop plot than in the intercropped plots, whereas parasitism also significantly increased with increasing hedgerow spacing. However, at both sites, larval and pupal mortality were unaffected by the vegetation structure. The oviposition preference of the predatory Chrysopa species was not influenced by the cropping system.