This is the same disease which occurs on the peach, apple and other plants, a list of which appears on page 108. It is called Crown Gall, crown knot, root-tumor and Black Knot (Fig. 66). Certain varieties are found to be more susceptible to the disease than others. In many localities the growing of varieties of grapes susceptible to Crown Gall has become unprofitable. Susceptibility is believed by certain authorities to vary with the susceptibility to Frost Injury; others hold that sap-acidity is a factor in determining susceptibility. Among the kinds resistant to Crown Gall may be noted: Concord, Catawba, Delaware and other American varieties. European grapes are more susceptible, and some of these, arranged in order of their susceptibility, follow: Muscat of Alexandria, Mission from California, Malaga varieties and Flame Tokay. Crown Gall apparently affects the grape wherever it is grown. The disease is reported from France, Germany, Italy, England, Holland, Denmark, Chili, New South Wales, Cape Colony, Canada and Mexico. In the United States, it has been found more particularly in California, New Mexico, Texas, Arizona, Washington, Oregon, Colorado, Arkansas, Nebraska, Missouri and Iowa. It was common in California as early as 1880. The earlier records give the impression that it was very destructive, but now the disease is not regarded as being of great economic importance. In cases of severe attack, vines are stunted, the leaves are smaller and chlorotic, and even unfruitfulness has been observed. (See more complete account under Apple, page 108.)

Fig. 66.   Crown Gall disease on grape   cane.

Fig. 66. - Crown Gall disease on grape - cane.

References

Hedgcock, G. G. Field studies of the Crown Gall of the grape. U. S.

Agr. Dept. Plant Indus. Bur. Bul. 183: 7-29. 1910. Blunno, M. A. Cancerous disease of the grapevine. New South Wales Agr. Gaz. 12:1079-1081. 1901. Garcia, F. European grapes. Observations on the Crown Gall. New Mexico Agr. Exp. Sta. Bul. 58: 19, 28-29; also 30 - 31. 1906.