366 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION. 



no conclusions whatever could be drawn. This much, however, was 

 very evident from observation, that a very large amount of blight 

 developed on many of the sprayed trees and that no decided benefit in 

 the season's crop of nuts had been obtained by the spraying. Even 

 where trees or branches had been perfectly and entirely coated with 

 heavy lime-sulphur solution, a large number of blighted nuts appeared. 



As a result of our experience in 1906, first with the cost, difficulty, 

 and slowness of spraying large walnut trees, and second with the lack 

 of effect of such spraying, we became thoroughly convinced that the 

 possibilities of walnut blight control did not lie in this direction. 

 Furthermore, as the prospect of obtaining varieties of the walnut more 

 or less immune to the disease, and likewise of much better quality and 

 much greater production than the average seedlings, became brighter 

 and brighter the undesirability of spraying methods became still more 

 pronounced. For these reasons no further extensive spraying experi- 

 ments were made by us and we still believe that the ultimate control of 

 walnut blight does not lie in this direction. It should be stated, how- 

 ever, that during the following year, that is in 1907, the appearance of 

 the trees sprayed in the spring of 1906 gave some reason to believe that 

 the blight was less prevalent on the sprayed than on the unsprayed trees. 

 This was particularly true in the case of trees sprayed with lime- 

 sulphur. It is, therefore, not improbable that while infection of the 

 nuts during the year when the spraying was done was not prevented, 

 that the twig and shoot infection was somewhat controlled and that on 

 this account less blight was carried over winter and less nut infection 

 took place the following year. It is further possible and quite likely 

 that thorough spraying year after year would have a cumulative effect 

 and might eventually reduce the amount of blight to a noticeable and 

 satisfactory extent. Even if this were true, however, we have not felt 

 that it would be practical to accomplish this to any general extent on 

 account of the reasons mentioned above. 



During the past season or two there has been a considerable revival of 

 interest in walnut spraying in one portion of the State, namely, in 

 Santa Barbara and Ventura counties. This has been due to the impor- 

 tance of the walnut industry in that region, the serious prevalence of 

 blight, and to the fact that a certain proprietary remedy or mixture has 

 received considerable prominence in that locality and has been used in 

 a large part of the spraying which has been done there. Walnut spray- 

 ing having thus become somewhat customary in the counties mentioned, 

 some work has been done there with Bordeaux mixture and various other 

 materials which have suggested themselves to the growers. We do not 

 wish to discourage such attempts at blight control in a region where 

 some of our oldest and finest seedling groves exist, one which is espe- 



