Occurrence of Fruit-Decaying Fungi on Adult Male Mediterranean Fruit Flies (Ceratitis capitata) Captured in Orchards and Adjacent Vineyards

Abstract

The occurrence of adult male Ceratitis fruit flies and their potential to transmit fungi associated with pre- and postharvest decay of fruit in natura were investigated. Sensus fruit-fly traps were installed in orchards each bordering on a vineyard on farms in the Stellenbosch region, South Africa.  Ceratitis fruit flies were collected weekly, identified and counted to determine the fluctuations in fruit-fly population levels. Captured fruit flies were plated on a semi-selective medium and the number of flies yielding the fungi was recorded. Both the Mediterranean fruit fly (C. capitata), and the Natal fruit fly (C. rosa) were trapped. C. rosa seldom occurred and comprised only 1 % of the total number of flies captured. Fruit-fly patterns showed that early infestation of orchards may contribute to the infestation of adjacent vineyards later in the season. At localities where flies were not trapped in the early season, infestation usually occurred in the orchards and adjacent vineyards in the late season, and well after fruits were harvested. Fruit flies from all localities yielded species of Alternaria, Penicillium, Aspergillus, Rhiwpus, Mucor and Botrytis cinerea on the medium. Of the different fungi, Alternaria and Penicillium spp. were most commonly carried by the flies at the various localities. The organisms occurred in a specific pattern on flies captured at a specific locality, and in a given orchard or vineyard. The pattern of fruit-fly infestation and their fungal contamination suggest that the Mediterranean Fruit-fly has the potential to transfer fungi associated with post-harvest decay in natura from early-season to mid- and late-season peach and plum orchards, and to neighbouring mid- and late-season wine and table grape vineyards. This highlights the importance of fruit-fly management in order to control disease epidemics in orchards and vineyards.