28 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION. 



soils if the plants growing in said soils happen to be sensitive to the 

 disease, and climatic conditions a wet Avinter, for instance -are 

 favorable. 



In the case of the rapid form of the Root-rot affecting the young 

 vineyard above mentioned, we know that the land was full of decaying 

 roots and other debris from the oaks that had been grubbed out; we 

 also know that Rupestris St. George is very sensitive to this disease, 

 and, furthermore, that the latter part of last winter was wetter than 

 usual. 



The intensive and rapid growth of the Root-rot in a three-year-old 

 vineyard grafted on Rupestris St. George, and established in a soil 

 which, from its situation and friability, would be considered unfavor- 

 able to the development of the parasite, is beyond a doubt exceptional. 

 However, this particular case has been dwelt upon, less on account of 

 its economic importance than for the fact that it demonstrates very 

 conclusively the sensitiveness of the Rupestris St. George to Root-rot, a 

 point which we shall have occasion to dwell upon again. 



Vines affected with the rapid form of the Root-rot can not, of course, 

 be saved. Vines affected with the usual form are, when treate'd before 

 the disease has made much progress, amenable to treatment. The pre- 

 ventive treatment here recommended applies equally well to both forms 

 of Root-rot. 



The remedial or preventive measures used in combatting the Root-rot, 

 or indeed any other disease attacking the subterranean organs of plants, 

 are, at best, but palliatives. As the disease is more general in soils with 

 an impermeable substratum that are quite retentive and miry after 

 heavy rains, adequate drainage is and will always remain the only 

 valuable preventive and curative measure. For excessive humidity is 

 the exciting cause of the disease; it favors fungous development, and the 

 tissues of the roots are soft, gorged with water, and in no condition to 

 resist the attacks of parasites. An author (Mr. P. Viala*) who has 

 studied the Pourridie of the vine and fruit trees with particular care, 

 says: "One must, to prevent the disease from spreading, and to protect 

 one's self against it in new plantations, thoroughly drain the soils in which 

 it exists, and also those that are, through their retentiveness, favorable 

 to its development." "Drainage is an excellent preventive measure," 

 he continues, "and what is more, the only efficacious one." But as 

 drainage is not always economically possible, a few half measures that 

 are at least useful may be mentioned, even if they have not the virtue 

 of an elixir. 



As soon as the disease shows in the vineyard, all badly diseased vines 

 (that is, those vines whose scant growth shows that their main root- 

 system is seriously attacked) should be removed and the vines surround- 



*Loc. cit., page 248. 



