10 FIELD STUDIES OF THE CROWN-GALL OF THE GRAPE. 



The crown-gall or a similar disease is thus reported on grapevines 

 in Europe from Germany, France, Italy, Denmark, and England; in 

 North America, from the United States, Canada, and Mexico; in 

 Australia, from New South Wales; and in Africa, from Cape Colony. 



In the United States the disease occurs in nearly every locality 

 where varieties of Vitis vinifera are grown. It occurs on some 

 American varieties in Canada and various portions of the United 

 States. The author has observed the disease in localities in the fol- 

 lowing States and Territories: Washington, Oregon, California, Ari- 

 zona, New Mexico, Colorado, Texas, Arkansas, Nebraska, Missouri, 

 and Iowa. 



DISTRIBUTION OF THE DISEASE ON SPECIES AND VARIETIES OF GRAPES. 



In the United States, as well as in foreign countries, the varieties 

 most susceptible to the disease belong to the species Vitis vinifera. 

 There are a few exceptions to this rule, especially in the northern 

 United States (41) and Canada (20), where varieties, hybrids or 

 crosses, of Vitis labrusca, Champion, Salem, and others are attacked 

 by the form of the disease on the canes. Varieties of Vitis linsecomii 

 and Vitis aestivalis are occasionally diseased on both canes and roots. 

 Varieties of Vitis rupestris are rarely attacked by either of the forms 

 of the disease and appear to be nearly immune. Data will be given 

 later in this bulletin on the resistance of individual varieties of several 

 species. 



DISTRIBUTION OF THE DISEASE ON YOUNG AND OLD VINES. 



The disease has been found to a limited extent on the roots of year- 

 ling vines of Vitis vinifera in vineyards and nurseries in Texas, Ari- 

 zona, New Mexico, California, Oregon, and Washington. It is most 

 common on the roots and canes of older vines, increasing in extent as 

 the vines grow older. The oldest vineyards usually contain the 

 highest percentage of diseased vines. 



IMPORTANCE OF THE DISEASE. 



In Germany, France, and Italy earlier writers report whole vine- 

 yards destroyed by the crown-gall. Later writers minimize the 

 importance of the disease. This decrease of disease is no doubt 

 due largely to the use of American varieties of grapes and their 

 hybrids for ingrafting with varieties of Vitis vinifera in the replant- 

 ing of vineyards destroyed by the phylloxera. It may also be due 

 to the gradual selection of the more resistant European varieties 

 by growers of grapes. Our observations and experiments sustain 

 such a conclusion, since American varieties are more resistant to 



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