BULLETIN 231] WALNUT CULTURE IN CALIFORNIA. 365 



found in all this work that to spray large walnut trees thoroughly is 

 an. extremely slow, difficult, and expensive operation. In the case of 

 the largest trees no attempt was made to spray more than two thirds 

 of the tree from the bottom up, inasmuch as the top could not be 

 thoroughly covered without using a very high platform. Our experi- 

 ence was that to spray a good sized tree thoroughly or to cover even 

 two thirds of an extra large tree required at least twenty gallons of 

 material. We found further that with the outfit used, consisting of 

 three men to spray and one to mix, not more than fifty good sized 

 trees could be sprayed in one day, while with the largest ones thirty 

 was about the limit of a day's work. It was found further that even 

 when the work was done with apparent thoroughness on these large 

 trees many portions of the top remained unsprayed the first time 

 over. This was detected particularly in spraying with lime-sulphur, 

 where the sprayed and unsprayed portions of the tree showed up in 

 strong contrast as soon as the spray had dried. For this reason it was 

 found necessary with these large trees to go back over them sometimes 

 two or three times in order to be sure that every twig and branch 

 which might harbor blight lesions was covered with the spray. As 

 regards expense, we found that we could not thoroughly spray good 

 sized trees for less than about 50 cents each, counting labor and 

 materials, while with many of the largest trees the outlay amounted to 

 at least $1.00 per tree even though the top of the tree was not sprayed 

 at all. As a result of this experience we were led very soon to believe 

 that the general spraying of California walnut groves for blight con- 

 trol would be extremely difficult of accomplishment during the period 

 of time available for such work, and also that it would be extremely 

 difficult, if not absolutely impossible, for the average grower to get 

 the work done thoroughly enough, even though the spraying done by 

 ourselves should prove extremely effective in controlling the disease. 



During the summer following our spraying careful observations 

 were made from time to time of the condition as to blight of the sprayed 

 and unsprayed trees in the experimental orchards. From such obser- 

 vations no difference whatever in the prevalence of the disease on the 

 nuts could be detected. Many of the sprayed trees lost a large portion 

 of their crop from blight, and even on individual, rather small trees 

 or individual branches which had been especially well sprayed and 

 absolutely covered with the mixture much blight developed on the nuts, 

 and it soon became apparent that no satisfactory degree of control, if 

 any, had been secured by our work. In the fall weighings were made 

 of the crop from the various trees and blocks, but owing to the extreme 

 variation in the crop of individual seedling trees the result was the 

 same as in our fertilizer experiment described on page 185, namely that 



