544 Report of the Entomologists. 



Only two applications were made on plots 2 and 3, the first on 

 May 5th and the second on June 19th. ' 



Plot 2 was sprayed with green arsenite mixed with water 

 and lime in the same proportion as for plot 1. Plot 3 was 

 sprayed with arsenate of lead at the rate of ten pounds to 150 

 gallons of water. 



These experiments demonstrated that one of the most seri- 

 ous difficulties in applying the poisons for the " willow beetle " 

 is the fact that the mixture does not spread well upon the wil- 

 low leaf. The glazed surface of the leaf is evidently accountable 

 for this. The arsenate of lead did not adhere well. The use 

 of glucose did not prove a success. Glue, in the proportions 

 used, proved more satisfactory than glucose. Although the in- 

 sects were found in all stages of development on all of the plots, 

 none of the spraying had any noticeable effect, except on plot 

 2, where green arsenite was mixed with glue and applied 

 with a knapsack sprayer. The fact of the poison being more 

 effectual in this case was undoubtedly due to the glue, which 

 made it adhere to the leaves. 



An important point in connection with spraying willows for 

 this insect is that the larvae and the beetles feed largely on 

 the under side of the leaves and in protected places near the 

 tips of the willows. This makes it a difficult matter to reach 

 them even with a knapsack sprayer and practically impossible 

 with the average power sprayer. The knapsack sj)rayer might 

 be used in some cases, but many of the fields of willows are so 

 large that it would bo impractical to depend upon the knapsack 

 alone. 



These difficulties have caused most of the willow growers to 

 give up spraying and to depend upon the machines for catching 

 the larvie and beetles. This method is described in the Four- 

 teenth Annual Report of this Station, pages 557 and 558. 



