Non-abscised aborted fruits are a source of inoculum for fungal pathogens causing fruit decay in sweet cherry

Disease incidence of non-abscised aborted and healthy sweet cherry fruits was investigated during two growing seasons. Fruits from two cultivars ('Van' and 'Lapins') were assessed weekly during 4 to 6 weeks in June and July until 3 to 4 weeks prior to harvest. The fruits were either surface-sterilized (in 0.5% NaOCl) or dipped in distilled water, both for 1 min, prior to incubation at 20 degrees C for 7 days in saturated air. Visible symptoms of fungal diseases were recorded at 1, 2, 3, 4, and 7 days after incubation. Aborted fruits had much higher disease incidence after incubation than healthy fruits. In 1999, the mean disease incidence was 56.3 and 15.8% in aborted and healthy 'Van' fruits, respectively. The following year, the mean disease incidence in 'Van' was 63.0 and 1.4% in aborted and healthy fruits, respectively. Corresponding numbers for 'Lapins' in 2000 were 80.6 and 9.0%. Surface-sterilized fruits were less decayed than non-sterilized fruit, but differences were not significant. After incubation commenced, symptoms always appeared earlier in aborted compared to healthy fruits. The most frequently observed fungal pathogens were Monilinia lava, Colletotrichum gloeosporioides, and Botrytis cinerea. A higher disease incidence and more rapid disease development in aborted fruits indicated that these were more vulnerable to fungal colonization than healthy fruits early in fruit development. Thus, non-abscised aborted fruits may act as important hosts of secondary inoculum for healthy fruits.