RESISTANT VINES AND THEIR HYBRIDS. 



GENERALITIES REGARDING RESISTANT VINES. 

 (Abstract from Bulletin No. 131, by F. T. Bioletti.) 



The most satisfactory method of combating phylloxera is the use of 

 resistant vines, because it is applicable to all conditions and is the most 

 economical in the end. A resistant vine is one which is capable of keep- 

 ing alive and growing even when phylloxera are living upon its roots. 

 Its resistance depends on two facts: first, that the insects do not increase 

 so rapidly on its roots; and second, that the swellings of diseased tissue 

 caused by the punctures of the insects do not extend deeper than the 

 bark of the rootlets and are sloughed off every year, leaving the roots 

 as healthy as before. The wild vines of the Mississippi States have 

 evolved in company with the phylloxera, and it is naturally among 

 these that we find the most resistant forms. No vine is thoroughly 

 resistant in the sense that phylloxera will not attack it at all; but on 

 the most resistant the damage is so slight as to be imperceptible. The 

 European vine ( Vitis vinifera, L.) is the most susceptible of all, and all 

 the grapes cultivated in California, with a few unimportant exceptions, 

 belong to this species. Between these two extremes we find all degrees 

 of resistance, which is expressed by a series of numbers ranging from 20, 

 indicating the highest possible resistance, to 0, indicating the utmost 

 susceptibility. The following table shows the resistance (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 rotundifolia _. 19 Gloire de Montpellier (Riparia). 18 



Vitis vulpina ( Riparia) 18 Riparia X Rupestris 3309 18 



Vitis rupestris _ 18 Rupestris Martin 18 



Vitis Berlandieri _ 17 Rupestris St. George 16 



Vitis sesti valis .._ 16 Riparia X Solonis 1616 16 



Vitis labrusca 5 Solonis. 14 



Vitis Californica 4 Lenoir _ ..12 



Vitis vinifera Isabella.. ....J 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 exceptionally with vines having a 



