THE BEAN FLY, OPHIOMYIA-PHASEOLI (TRYON) (DIPT, AGROMYZIDAE), AND ITS PARASITOIDS IN ETHIOPIA

Surveys carried out during two seasons showed that the bean fly (BF), Ophiomyia phaseoli (Tyron), is widely distributed in Ethiopa. It was found on haricot beant (Phaseolus vulgaris L.), cowpea (Vigna unguiculata L.) and soybean (Glycine max [L.] Merr.) but caused economic damage only on haricot bean. The leguminous bush Crotalaria laburnifolia L. was the only wild host plant supporting BF and its parasitoids throughout the year in some parts of Ethiopia. These surveys confirmed that Ophiomyia phaseoli is the only species of bean fly found in this country. Bean fly incidence on the wild host was highest during the dry season, between December and March. Seventeen species of parasitoids were recorded. Of these, the pteromalids Sphegigaster stepicola Bouc. and S. brunneicornis (Ferr.) were the most common species on the wild plant host, accounting for up to 44.5 % (xBAR = 26.2 +/- 3.1 %; xBAR +/- se) of BF parasitism. Parasitism by the braconid Opius phaseoli Fischer was low, ranging from 0 % to 23.2 % (xBAR = 5.6 +/- 1.3 %). However, on haricot bean, it was the major parasitoid, with over 87 % of BF parasitism. This fact suggests the possibility that the host plant plays an important role in BF dynamics.