EFFECTS OF UREA ON THE FORMATION OF APOTHECIA AND WINTER CONIDIA OF BLUMERIELLA-JAAPII (CHERRY LEAF-SPOT) AND ASSOCIATED MICROFUNGI ON OVERWINTERED CHERRY LEAVES

Sour cherry leaves infected with the cherry leaf spot pathogen, Blumer iella jaapii, were collected at the time of leaf-fall and dipped in wa ter or 5 % urea solution. Dipping in urea had an immediate but no long terms effect on the nitrogen and the C/N ratio of the More colony for ming units of Cladosporium spp were recovered from leaves dipped in ur ea than from the control leaves dipped in plain water. Trichoderma spp . were isolated on all 3 isolation dates and increased although the po pulation of Trichoderma spp. increased earlier in leaves dipped in ure a, by April Trichoderma spp. were most numerous in the water-treated l eaves. Stromata of B. jaapii on leaves treated with water produced an abundance of acervuli and apothecia. By contrast, stroma development w as arrested and apothecia and by winter conidia were completely inhibi ted by y the urea treatment. This is the first report of the control o f B. jaapii with urea, and of the occurrence of Trichoderma spp. in ov erwintered cherry leaves.