. Diseases of fruits and nuts. Fruit; Nuts. Diseases of Fruits and Nuts 75 Black Rot.—In this disease, caused by the fungus Guignardia Bid- wellii, brown or black spots appear on the leaves and canes. The berries rot, blacken, dry up, and become hard, wrinkled mummies which cling- to the vine all winter. This is the most destructive disease of grapes east of the Rocky Mountains but has never been seen in California. Frequent spraying as for anthracnose is necessary to control black rot. Bunch Mold.—A gray or black mold often develops in the clusters of ripe grapes and spoils many of the bunche
. Diseases of fruits and nuts. Fruit; Nuts. Diseases of Fruits and Nuts 75 Black Rot.—In this disease, caused by the fungus Guignardia Bid- wellii, brown or black spots appear on the leaves and canes. The berries rot, blacken, dry up, and become hard, wrinkled mummies which cling- to the vine all winter. This is the most destructive disease of grapes east of the Rocky Mountains but has never been seen in California. Frequent spraying as for anthracnose is necessary to control black rot. Bunch Mold.—A gray or black mold often develops in the clusters of ripe grapes and spoils many of the bunches (fig. 30). This is caused by various fungi, especially Botrytis cinerea and Aspergillus niger. Fruit in transit is sometimes attacked by similar fungi. No practical method. rig. 30.—Bunch mold of grapes. has been found of preventing the development of mold in bunches of grapes on the vine. California Vine Disease, Pierce's Disease.—In this disease, appar- ently caused by a virus, the vines gradually weaken, the growth becomes short, dieback of the canes develops, and the whole vine soon dies for no obvious reason. In some varieties there is a yellowing between the veins of the leaves and the fruit withers and dries in summer. The disease spreads in the vineyard. This trouble, which has become rather serious in certain districts during the last seven years, resembles the disease which caused widespread destruction of vines in southern California'' and in the Santa Clara Valley almost fifty years ago. Affected vines should be removed when the first symptoms are seen. Replants in the same places do not seem to contract the disease. Coulure, Shelling.—In certain varieties, notably Muscat, many of the flowers fail to set fruit, which results in the production of poorly filled bunches. This may be due in part to poor pollination or fruit setting 18 Pierce Newton B. The California vine disease. U. S. Dept. Agr. Div. Veg. Path. Bill. 2:1-222. 25 pi. Please note that
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