SUMMARY OF EXPERIMENTS OF 1899. 



H. P. GOULD, S. W. FLETCHER AND G. W. CAVANAUGH. 



I. The Season's Experience with the San Jose Scale. 



The results of experiments in spraying for the San Jose scale 



were detailed in Bulletins 14:4: and 155. During the past year these 

 experiments were continued more extensively. The former con- 

 clusions were fully confirmed. The infested stock was mainly apple, 

 pear, plum, almond and willow trees, all of medium size or below. 

 Some were very badly infested, but all had made a fairly vigorous 

 growth in 1898. Experiments in 1898 had shown that a 20 per 

 cent mechanical mixture of kerosene and water was the most effi- 

 cient spray, so no other proportion was used this year. The first 

 application in 1899 was made to one lot of trees on April 10 and 11, 

 when the weather was favorable for rapid evapoi'ation. This is a 

 very important point in all spraying with im-emulsified kerosene. 

 Another lot of trees was sprayed on June 6 and were, of course, in 

 full leaf at the time of spraying. A few badly infested currant 

 bushes were left as checks. 



On June 23, the young scale insects were numerous on the 

 unsprayed currants and a very few were found on the sprayed trees, 

 indicating that the insecticide had killed most, but not all of the old 

 scales. On one of the worst infested trees which had been sprayed, 

 but a single live scale could be found. The trees sprayed in June 

 showed more live scales than any of those sprayed in eaj-ly spring. 



All of the trees were sprayed a second time on June 21:, and 

 three with very dense heads again on June 29. At this date, Dec. 

 11, few live scales can be found on the sprayed trees — mostly on 

 apples and pears, where some insects were protected from the 

 spray by irregularities of the bark. On the smooth barked willows, 

 every scale was killed. On the whole the results are encouraging. 

 We feel sure tliat the San Jose scale can be held in check by spray- 

 ing whenever the infested plants can be thoroughly treated. If the 

 trees had been sprayed again in latesunnuer, probably all the insects 



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