THE PREVENTION OF CROWN-GALL. 27 



additional number of resistant varieties will be determined from 

 this experiment. 



RESISTANT STOCKS SHOULD BE USED FOR GRAFTING NONRESISTANT 



VARIETIES. 



The Rupestris St. George variety gave the highest degree of resist- 

 ance to the disease and grew vigorously. This variety is of no value 

 except as a stock for the purpose of bench grafting. Its resistance 

 to the disease being very high makes it a valuable vine for this pur- 

 pose. Its resistance to the phylloxera makes it doubly valuable, 

 since sooner or later this pest will be likely to appear in every vine- 

 yard region where European varieties of grapes are grown. 



The Lenoir variety, used as a stock for grafting, is also valuable as 

 a wine grape. Although quite a number of vines of this variety 

 became slightly diseased in the experiments, none were seriously 

 affected, and it is recommended as a good vine for the Southwest 

 wherever the crown-gall has appeared, either when grown for its fruit 

 or as a stock for ingrafting more susceptible varieties. It is not within 

 the province of this bulletin to enter fully into the discussion of all 

 the varieties of vines resistant to the phylloxera, most of which will 

 very probably be found resistant to the crown-gall. 



In localities where the ravages of the disease are marked, it is not 

 advisable to plant the Mission variety, especially the Mission from 

 California, the Muscat of Alexandria, Flame Tokay, Rose of Peru, 

 Malaga, Burgundy, or Riesling varieties unless grafted upon resist- 

 ant stocks. 



OTHER MEANS OF PREVENTION. 



When vines are grown from cuttings, care should be taken to 

 secure cuttings from vineyards free from the disease. Such cuttings 

 should be grown in soil where vines have not been grown for five 

 or more years. 



In planting vines or cuttings in the arid regions it is best to plant 

 them deeply, so that not more than one bud or eye will remain above 

 the soil. This will protect them both from freezing and from the 

 burning sun, both of which are injurious to the young vines and 

 lower their vitality even though an entrance of the disease may not 

 take place. 



In case a vineyard or locality is free from crown-gall it is best to 

 be exceedingly careful where vines are purchased for planting. That 

 the nursery is free from the disease should be ascertained before pur- 

 chasing varieties of European grapes. It is better, where possible, 

 to propagate vines by bench-grafting on healthy stocks grown at 

 home from cuttings selected from healthy vines. 



183 



