HOST RANGE FOR STEMBORERS AND ASSOCIATED NATURAL ENEMIES IN DIFFERENT FARMING SYSTEMS OF KENYA

The geographical distribution and grass host range for stemborers and their natural enemies were assessed in three districts of Kenya between June 2002 and August 2003. In each district, grasses were sampled and dissected for presence of stem borers and/or their parasitoids (natural enemies). This was done in three cropping systems; (a) maize (Zea mays) surrounded by wild grasses, (b) sorghum (Sorghum bicolor) surrounded by wild grasses and (c) uncultivated grasslands. Busia and Suba districts had the higher diversity of stemborers than Machakos district. Similarity, parasitoids diversity was highest in Busia (24), followed by Suba (19) and the least in M achakos (9). Thirty-four species of stemborers belonging to the orders: Coleoptera [Anthribidae (1), Cerambycidae (3), Curculionidae(7), Mordellidae (3), Languriidae (3), and Tenebrionidae (2)]; and Lepidoptera [Noctuidae (6), Pyralidae (7), Cossidae (1), and Tortricidae(l)] were recovered from 31 grass species. Grass species that accounted for the highest diversity of stemborers were Hyparrhenia (Hyparrhenia rufa), Barnyard grass CEchinochloa pyramidalis), Guine grass (Panicum maximum), Guinea-fowl grass (Rottboellia cochinchinensis) and wild sorghum (Sorghum versicolor), Lemon grass (Cymbopogon afronardus), Hyparrhenia (Hyparrhenia rufa), Guine grass (Panicum maximum) and sporobolus (Sporobolus pyramidalis) were grass species with the highest parasitoid diversity.