Assessment of the potential of Napier grass (Pennisetum purpureum) varieties as trap plants for management of Chilo partellus

Ten Napier grass [ Pennisetum purpureum Schumach ( Poaceae)] varieties, used in various parts of Kenya as animal fodder, were tested for their potential role as a trap crop in the management of the gramineous spotted stemborer, Chilo partellus ( Swinhoe) ( Lepidoptera: Crambidae), through habitat manipulation. Oviposition preference and larval survival and development were determined for each of these varieties under laboratory and screen-house conditions. Two-choice tests revealed that seven of the varieties tested were preferentially chosen by gravid female moths for oviposition over a susceptible maize cv. Inbred A. Larval survival was significantly lower on the majority of the Napier grass varieties ( about 10%) than on maize cv. Inbred A ( about 60%). Similarly, larval development was about 2 weeks longer on the majority of the Napier grass varieties. It was concluded that four of the varieties tested ( Bana, Ex-Machakos, Gold Coast, and Ex-Nyanza-2) had potential for use as trap crops in C. partellus management because they were more preferred by the borer moths for oviposition and allowed minimal survival of the larvae. This minimal larval survival is desirable in the conservation of C. partellus natural enemies when the cultivated host plant is out of season.