In Okayama Prefecture, apothecia of the fungus causing brown rot of peach (Monilinia fructicola) were found for the first time in the western part of Japan in 1990. Maturity of the apothecium coincided with flowering of peach in early April. M. fructicola produced numerous conidia on the leaves and twigs with leaf curl, mainly from mid May to late June. Isolates of M. fructicola from ascospores produced on mummified fruits were pathogenic on peach flowers. These results show that the primary inoculum source, the ascospores of apothecium of M. fructicola, and the secondary inoculum source, conidia on leaves with leaf curl are infection sources for peach brown rot in Okayama Prefecture.
Leaf blight, shoot blight and cluster rot of grape in plastic houses and glasshouses were found in Okayama Prefecture in 1996. Leaf blight caused leaves to droop after the petiole base had browned, mainly in short pruning culture. Shoot blight occurred mainly in long pruning culture. These symptoms developed more frequently in the plastic house, especially with early forcing. The symptoms on fruit clusters were of two types, cluster rot and dry rot. The isolates of Dothiorella sp. isolated from these lesions at a high frequency were pathogenic on petioles, fruit clusters and berries of grape. Thus, leaf blight, shoot blight and cluster rot were the same disease. The name cluster rot (Fusagare-byo in Japanese) was proposed for the disease.
Yam mild mosaic virus (YMMV) was detected by RT-PCR from Dioscorea alata plants infected with Japanese yam mosaic virus (JYMV). The infection with YMMV was further comfirmed by nucleotide sequencing of the 3'-terminal region of the virus. RT-PCR assay for 52 D. japonica, 39 D. opposita, 9 D. alata plants with virus-like symptoms indicated that YMMV and JYMV were detected, but Yam mosaic virus was not detected from yam plants in Japan.