December, '15] MATHESON: POPLAR AND WILLOW BORER 



523 



the young larvae have begun actively feeding. This seemed very rea- 

 sonable, owing to the quite exposed condition of the young larvae in 

 their burrows. It seemed to me that some of the emulsions ought to 

 penetrate the outer bark or be absorbed through the very small amount 

 of frass at the entrance to the burrows and destroy them. With this 

 conclusion, I determined to try varying strengths of miscible oils and 

 kerosene emulsion applied both in the fall and spring. In order to 

 secure a stronger penetrating fluid, it was felt carbolineum avenarius 

 ought to be given a thorough trial, but I had to go very slowly as very 

 little is known about the constituents of this preparation. Furthermore, 

 very little is known as to its effects on actively growing or dormant trees. 



In the fall of 1913, seventy-six badly infested two-year-old poplar 

 trees were secured and planted at the insectary. On December 1, 1913, 

 part of this block was treated with scale cide at varying strengths and 

 also a few trees with carbolineum and its emulsion^ as indicated in the 

 table. This experiment was closely watched the following spring but 

 no injury to the trees could be noted, except that the carbolineum 

 treated trees did not seem so vigorous. However, they grew and are 

 now (1915) large healthy trees. Examination and careful count of 

 the burrows in all of the trees was made on June 17, 1914. The 

 number of larvae present per tree is shown in table I. 



Table L Cryptorhynchus lapathi Linn. 



Treatment 



When 

 Applied 



Number 



Trees 



Examined 



Number 

 Infested 



Larvae 

 per Tree 

 (Average) 



Not 

 Infested 



Per Cent 

 Infested 



Scalecide 1-5 2 



Dec. 1, 1913 



10 



June 17, 1914 



3 



2.6 



7 



30 







10 





4 



1.25 



6 



40 



Scalecide 1-10 





10 





7 



2.3 



3 



70 



Scalecide 1-12 





10 





8 



1.9 





80 



Scalecide 1-15 





10 





5 



2 



5 



50 







2 





0 





2 



0 



CarboLneum Emulsion 1-2 





2 





0 





2 



0 



Check 





22 





10 



2.6 



12 



45.5 



In the spring of 1914 a series of experiments was undertaken in a 

 large nursery. Three-year-old stock was chosen as it was the most 

 available at the time of doing the work. Badly infested trees were 

 selected at one side of a large block which had been recently dug. 

 Directly across the roadway was a block of young poplars. On March 

 31 scalecide, of varying strengths, carbolineum, and carbolineum 

 emulsion were apphed to the trunks from the ground up to the young 



1 The carbolineum emulsion was prepared as follows: — lib. sodium carbonate, 

 1 quart hot water, 1 quart carbolineum avenarius. The sodium carbonate was 

 dissolved in the hot water and the carbolineum was then added, stirring vigorously. 



2 All dilutions are with water. 



