312 CALIFORNIA FRUITS: HOW TO GROW THEM 



DISEASES OF THE VINE 



One of the most prevalent diseases of the vine in California is caused 

 by a fungus which affects leaves, canes, and berries, and is locally 

 known as "mildew." This disease is recognized by grayish white color- 

 ing of the affected leaves, which, as the disease progresses, shrivel and 

 dry up ; the young cane also blackens and dries, and the berries show 

 whitish patches, which become darker colored and the berries crack 

 open. The usual remedy for the trouble is finely-ground or sublimed 

 sulphur applied several times during the season. Definite reference 

 may be found in the chapter on diseases of trees and vines. 



The Bordeaux Mixture and other copper preparations are some- 

 times useful upon grape-vines, as will be cited in the chapter on plant 

 diseases. 



Coulure. A frequent misfortune of the vine, and for which no 

 remedy is yet known, is coulure, a term signifying the failure of the 

 fruit to set or to remain on the cluster. This occurs in varying degrees 

 from the loss of a few berries to the almost complete clearing of fruit 

 from the stem. It is worse with some varieties than others and in some 

 localities than others. The trouble is believed to arise from various 

 causes. 



There is, also, occurring with more or less frequency, a reddening 

 and death of the vine leaves, supposed to be identical with the trouble 

 known to the French as "rougeole." The leaves show light-colored 

 spots at first, which afterward turn red and finally involve the whole 

 leaf or cane, and sometimes the whole vine. It usually occurs in mid- 

 summer, and is not necessarily fatal in its effects. 



Root Knot. An evil occurring on the main stem of the vine, 

 generally near the surface of the ground, is an excrescence of woody 

 character commonly called "black knot." There has been much dis- 

 cussion as to the cause of this abnormal growth, without full agree- 

 ment among observers. Some attribute the knots to injuries to the 

 stump in cultivation, others to outbursts of sap which the short pruning 

 system does not give top growth enough to dispose of, and to various 

 other causes, but the agency is now definitely known to be invasion by 

 bacteria. This is analogous to the "crown knot" of fruit trees which 

 will be mentioned in the chapter on plant diseases. 



Anaheim Disease. There has prevailed for several years in 

 California a mysterious disease of the vine known as the "Anaheim 

 disease," because its evil work first appeared in that vicinity. It de- 

 stroyed many thousand acres of vines and led to the abandonment of 

 grape growing in some regions in southern California. The fullest 

 statements concerning its performance can be found in Bulletin No. 2, 

 U. S. Department of Agriculture, Division of Vegetable Pathology, by 

 Newton B. Pierce, 1892, and Farmers' Bulletin No. 30, 1895. Fortun- 

 ately during recent years the trouble has been less aggressive but neither 

 its nature nor satisfactory treatment has been fully demonstrated. The 

 latest available information concerning it and other troubles of the vine 

 can be had by application to the University Experiment Station at 

 Berkeley. 



