This study was carried out to investigate the infection period, the susceptibility of several cultivars, and the effective control methods of apple rot caused by Botryosphaeria dothidea from 1978 to 1987. The results obtained were as follows;
1. The rot on fruits began to be observed from mid-or late July and showed its increment rate peak formed from mid-August to early October after which gradually decreased by late October.
2. The fruit infection throughout the whole fruit growing season started in early June and ended in late October with relatively higher infection percentage between June and July.
3. Higher natural infection percentage was observed on fruits from trees with many wart symptoms caused by the causal fungus than fruits from trees without wart symptoms.
4. In the observation of varietal differences on natural infection of rot during 1979 and 1980, cultivars Fuji, Orei, and Indo showed the most susceptible and followed by cultivars of Starking Delicious, Jonared, and Rall´s Janet showing moderate, and the cultivar Jonathan was resistant.
5. The rot disease was controlled effectively by bagging the fruit from June to September, yet when spraying was carried out from June to August at ten-day interval, Captafol-Wp or Bordeaux mixture of 4g/12g/ℓ was also effective in reducing the disease.
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