Field Surveys for Natural Enemies of Banana Weevil, Cosmopolites Sordidus (Germar), in Indonesia with Emphasis on Searches for Egg and Larval Parasitoids

The banana weevil, an important pest on highland banana and plantain in Africa, is endemic to southeast Asia where it usually occurs in low numbers. This suggested the possibility of effective co-evolved natural enemies in its original range that might be used in a classical biological of banana weevil. Previous searches for natural enemies in southeast Asia, undertaken in the first half of the 20th century, encountered only generalist predators. Therefore, a search was undertaken for natural enemies of banana weevil on the islands of Sumatra and Java in Indonesia with emphasis on looking for egg or larval parasitoids. Two surveys were conducted September-November 2000 and March-November 2001in which approximately 640 and 25,000 eggs were collected and reared in the first and second survey respectively. Evidence of egg parasitism was initially suggested by the presence of Hymenopterous wings and body parts in rearing containers, but further rearing of more than 25,000 eggs failed to uncover further evidence of parasitism. This suggests that egg parasitism in Indonesia is rare. To assess larval parasitism, the larvae were reared on pieces of banana corm. Several dipterans were found in larval rearing containers, but taxonomic identifications of phorids and other dipterans obtained suggested that none of these were parasitoids Phorids were probably scavengers whose eggs were present in banana corms when they were brought to the laboratory. During the second survey (March-Nov 2001) we developed improved methods for efficiently collecting and rearing of banana weevil eggs and larvae. These techniques will facilitate future parasitoids surveys and will be useful to behavioral and ecological studies of the banana weevil. A complex of predatory ants, including species ofMyrmicinae, Ponerinae, Formicinae and Dolichoderinae, were found associated with banana plants and residues in the field. Adults and larvae of the ant Myopopone castanea (authorname) (Hymenoptera:Formicidae:Ponerinae) were observed attacking banana weevil larvae in crop residues. Predators in the orders Dermaptera and Coleoptera were also encountered. Ofthese, the histerid Plaesiusjavanus Erichsen appeared to be most important. While most of the predators encountered were nonspecific and unlikely to be important in banana weevil control, there is need for further work on egg and larval parasitoids in other areas such as southern India, which is the center of origin for plantain. Plantains are comprised of clones with greater susceptibility to banana weevil