154 



UNIVERSITY OF CALIFORNIA EXPERIMENT STATION. 



a young vine very badly attacked, showing a large mass of knots at the 

 surface of the ground, and four on the stem above the surface. Such 

 a vine is almost girdled and could never develop into a healthy plant. 

 Figure 17 shows the appearance of the knot on a branch or arm. In 



this case the knots could be 

 removed and the vine might 

 recover perfectly^ 



It is not uncommon to find 

 vines with large masses of 

 knots on all sides of the trunk 

 and on all the arms, which 

 yet make a vigorous growth 

 and produce good crops. 

 When the knots extend all 

 around the trunk of an old 

 vine, however, it may be 

 girdled, and, while it seldom 

 dies, it may become weak and 

 worthless. 



Various theories have been 

 advanced as to the cause of 

 this disease, but the most com- 

 monly accepted is that it is 

 due to abrupt changes of tem- 

 perature, and especially to 

 autumn frost occurring before 

 the vine has become thor- 

 oughly dormant. This cause 

 alone, however, does not seem 

 to be sufficient to cause the 

 disease. The knots appear 

 only on vines growing in 

 moist places, and especially 

 in sandy soil in the hotter 

 regions. 



Anything which causes a 

 vine to grow vigorously late 

 in the season and prevents the proper ripening of the wood, renders it 

 susceptible to the disease. 



In accordance with these ideas, the remedies advocated aim at caus- 

 ing the vine to ripen its wood early and completely. These remedies 

 are drainage of the soil, fertilization with phosphatic manures, longer 

 pruning, raising the trunk of the vine, and removal of the knots. 



FIG. 18. Coulured bunch of Muscat of Alexandria. 



