DISEASES OF CULTIVATED PLANTS 503 



similar to that of the brown-rot form of the downy mildew. It 

 occurs in Missouri and the Southwest and has been reported as rather 

 serious in some parts of Ohio. There is nothing in the nature of 

 this disease, so far as known, to indicate that it can not be satis- 

 factorily controlled by the treatment recommended for black-rot. 

 Sufficient knowledge of .this subject to justify a positive statement 

 in regard to treatment is not at present available. (F. B. 284.) 



California Vine Disease. Several vine diseases occur on the 

 Pacific coast which cause heavy losses. The most serious one, how- 

 ever, is the California vine disease, which has already killed more 

 than 30,000 acres of the most thrifty and productive vineyards. 

 This disease may be placed among the most destructive as well as 

 the most obscure of all plant maladies. Considering its injurious 

 nature, the obscurity of its cause, and the extent of its ravages, it 

 may 'be classed with peach yellows. 



The effects of the disease are seen the first season on the foliage 

 of the vine, but by the second season a reduced growth of the cane 

 is apparent. Taking the Muscat of Alexandria as an illustration of 

 the behavior of the disease, when the leaves of this variety are at- 

 tacked small yellow spots appear in the tissue between the main 

 veins ; as these spots enlarge they often unite, forming yellow strips, 

 which broaden and die at the center. Eventually there is a well- 

 marked brown stripe of dead tissue, bordered by yellow on each side, 

 leaving only a narrow band of green tissue along the veins. After 

 this the leaves fall, and as a result the immature portions of the 

 canes turn black and die. The next season the growth is short. 

 Often the color of the foliage is normal in the spring, becoming 

 spotted during the heat of summer, after which the premature fall 

 of the leaves and the death of the canes ensue as before. The follow- 

 ing spring the vine may fail to put forth new growth, or it may grow 

 until the heat of the summer and then die. This is a typical illus- 

 tration of the progress of the malady, which works in many ways. 

 In some instances the diseased vines appear perfectly healthy up to 

 the time of the vintage, when they suddenly die ; in other cases they 

 live from three to five years. 



The roots also show the diseased state of the vine at an early 

 period ; the growing points shrink and the rootcap begins to decay. 

 This decay is most apparent in the parenchyma or soft tissue sur- 

 rounding the wood bundles of the smaller roots. The soft parts rot 

 to such an extent that the cortical portion of the root may be easily 

 stripped from the wood. This decay progresses until nearly the 

 whole root system is involved. 



When the malady first appears in a vineyard its attacks seem 

 sporadic. The disease will show on a vine here and there or on 

 several vines in one section of the vineyard where some unfavorable 

 soil condition weakens the stocks. Gradually other vines become 

 affected, and the disease continues to progress and its virulence be- 

 comes more marked, until finally the vineyard is worthless. 



Studies of this malady have revealed the fa/ct that cuttings from 

 diseased vines are themselves diseased, and that the degree or amount 



