カキ西条における果皮黒変症状の種類と発生要因について

その他

Saijo, a leading astringent type cultivar of Japanese persimmon in Chugoku district, is susceptible to various types of disorders which appear on the surface of fruit and are called inclusively as black spot. These disorders impaired more or less the market value of fruits. In this report, we classified these disorders by means of visual symptoms into five types; cloudy, dotty, gutter, broken line-like and wavy types. Further, the times and causes of their occurrences and the influences of fungicide- and pesticidesprays on them were investigated. Results are summarized as follows ;
1. Although cloudy type disorder reduced the marketability of fruits to the greatest degree for its most noticeable symptom, the rate of its occurrence was about 6% in the non-sprayed trees, which was not so high as those of other types except wavy.
The susceptibility of fruits to this disorder varied with the positions of them in a tree, i. e. the fruits being located at the south side of tree often suffered from sunscald and such fruits tended to be very susceptible to it. Next to cloudy type, gutter and broken line-like types markedly degraded the market value of fruits. Among all types, gutter type occurred at the highest rate, followed by dotty, broken line-like, cloudy and wavy types in the order.
2. Dotty type disorder appeared at the beginning of July, but others did close to the harvest time, after the beginning of September.
3. It seems that dotty type disorder is caused by fungi because its occurrence was controled to some extent by the spray of Bordeaux mixture in June, July or August or by the sprays (main fungicide ; zineb wettable powder) programmed by the extension service in Shimane prefecture.
4. All types of disorders almost disappeared due to the covering of fruits with paper bags from June 20 to the harvest time.