Natural enemies of lepidopterous borers on maize and elephant grass in theforest zone of Cameroon

The importance, geographical and temporal distributions of parasitoids of l epidopterous borers on maize and elephant grass, Pennisetum purpureum, were assessed during surveys in farmers' fields in six villages and two on-stat ion trials in the forest zone of Cameroon between 1995 and 1996. The borer species encountered were Busseola fusca (Fuller), Sesamia calamistis Hampso n, Eldana saccharina Walker on both host plants, and Mussidia nigrivenella Ragonot on maize only. Busseola fusca was the predominant host accounting f or 44-57% and 96% on maize and elephant grass, respectively, followed by E. saccharina on maize with 27-39%. Fifteen hymenopterous, two dipterous;Ind one fungal species were found on these stem and cob-borers. Among those wer e six pupal, six larval, four egg, one larval-pupal parasitoid and four hyp erparasitoids. The scelionid parasitoids Telenomus busseolae Gahan and T. i sis Polaszek were found on B. fusca eggs in all locations. During the first season, mean egg parasitism was low and ranged between 3.1% and 27% versus 54-87% during the second season. Species belonging to the Tetrastichus atr iclavus Waterston complex were recovered from all four borer species. The m ajority and most common larval and pupal parasitoid species belonged to the ingress-and-sting guild. Larval and pupal parasitism were very erratic and on more than 50% of the sampling occasions no parasitoids were recovered. Parasitoid diversity was higher on elephant grass than maize.