ECOLOGICAL ASPECTS OF FUNGAL PATHOGENS AND DROSOPHILA SPECIES - V. R. Swart, W. J. Swart  & S. vdM. Louw

Centre for Plant Health Management, University of the Free State, Bloemfontein 9300

Cactus pear (Opuntia ficus-indica) is an important alternative crop in the semi-arid regions of southern Africa. From a management point of view, numerous insect pests and diseases have recently become problematic on the plant.  Vinegar flies (Diptera: Drosophilidae), are very common in cactus pear orchards where they feed and breed in mature fruit.  Drosophila spp. are known vectors of fungi and the objective of this study was to investigate whether D. melanogaster and D. hydei harbour and transmit fungal pathogens of cactus pear.  The ecological succession and fungal transmission potential of Drosophila spp. on the fruit of cactus pear was also studied.  Pathogenicity tests with isolated fungi on mature O. ficus-indica cladodes and fruits were positive for several of the fungal genera and Koch’s postulates were confirmed.  The most pathogenic fungus on cladodes and fruit was a species of Michrodochium.  Scanning electron microscopy confirmed the presence of fungal propagules on the exoskeleton of both Drosophila species.