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UNIVERSITY OF CALIFORNIA EXPERIMENT STATION. 



ance (according to Viala and Ravaz and other authorities) of some of 

 the best known species and varieties: 



Comparative Resistance to Phylloxera. 



SPECIES WILD VINES. 



CULTIVATED VARIETIES AND HYBRIDS. 



Vitis rotundif olia 19 



Vitis vulpina (Riparia) 18 



Vitis rupestris 18 



Vitis Berlandieri 17 



Vitis sestivalis 16 



Vitis labrusca 5 



Vitis californica 4 



Vitis vinifera . 



Gloire de Montpellier (Riparia) .... 18 



Riparia X Rupestris 3309 18 



Rupestris Martin 18 



Rupestris St. George 16 



Riparia X Solonis 1616 16 



Solonis 14 



Lenoir 12 



Isabella 5 



The degree of resistance necessary for the production of good crops 

 varies with the character of the soil. The resistance expressed by the 

 numbers 16 to 20 is sufficient for all soils. A resistance of 14 or 15 is 

 sufficient in sandy and moist, rich soils, where the vine can readily 

 replace the rootlets as fast as they are destroyed. Fairly successful 

 vineyards have been established with vines having a resistance of 

 less than 14, but as the vines become old the lack of resistance is 

 generally shown by a weakening of the vine and a falling off of the 

 crop. Many vineyards in the south, of France grafted on Lenoir which 

 formerly bore well, have now to be treated with injections of bisulfid of 

 carbon. For the above reason it is advisable to reject all vines with a 

 resistance of 13 or under, especially as vines with greater resistance 

 can now be obtained for practically all conditions. 



Resistant vines are of two kinds: (a) Those which are grown for the 

 grapes they produce, and (b) Those which are useful only as stocks on 

 which to graft the non-resistant varieties. The former are called 

 "Direct producers" and the latter "Resistant stocks." 



(a) Direct Producers. When the phylloxera commenced to destroy 

 the vineyards of Europe, the natural attempt was made to replace them 

 with the varieties of vines which had proved successful in the United 

 States, where the insect was endemic. These varieties, however, all 

 proved unsatisfactory. Some, like the Concord and Catawba, were 

 insufficiently resistant, and although they could be grown where the 

 severe cold of winter impeded the prolificness of the phylloxera, they 

 quickly succumbed in the milder grape-growing sections of Europe.* 

 Most of them were poor bearers compared with the prolific European 

 vines, and finally the character of their fruit differed so widely from 



* In California these and other Labrusca varieties and hybrids resist very little 

 longer than Vinifera vines. 



