THE POPLAR AND WILLOW BORER 473 



indicated by the amount of sawdust exuding from the numerous burrows. 

 All the trees treated with different strengths of scalecide showed just as 

 high a percentage of infestation as did the checks. This preparation had 

 no appreciable effect. In the trees treated with carbolineum, either pure 

 or as an emulsion, not a trace of infestation could be found. After a 

 search of several hours, one shriveled and blackened larva was discovered 

 in its burrow. It was not desirable, however, to injure the trees too 

 much by cutting into all suspicious egg punctures. 



The trees were again carefully examined on June 18, when the previous 

 observations were confirmed. The checks and the trees treated with 

 scalecide were nearly all badly infested, many trees having from eight 

 to ten borers present, while a few, both of the treated trees and the checks, 

 were apparently free from infestation. The trees treated with carbolin- 

 eum and its emulsion were growing even more vigorously than were the 

 untreated trees, and not a trace of the work of the borer in any one of 

 the twelve treated trees could be discovered. These preparations colored 

 the trunks of the trees deep brown, but other than that no injury could 

 be seen. 



Experiments in 1914-15 



In view of the possibility that such perfect control might be due to 

 other causes than the effect of the treatment, a larger series of experi- 

 ments was planned for the fall of 1914 and the spring of 1915. The 

 miscible oils were discarded, and kerosene emulsion, which had been recom- 

 mended for the control of the locust borer (Cyllene robiniai), was given a 

 trial. In a block of over ten thousand trees, ready for digging in the 

 fall of 1915, rows were selected at the end showing the greatest amount of 

 the feeding work of the beetles. On December 4, 1914, groups of twenty 

 trees each were treated respectively with pure kerosene emulsion, carbo- 

 lineum emulsion, and carbolineum. Rows for checks were left between 

 the treated rows. The material was applied directly to the trunks, up to 

 the younger growth. On April 9, 1915, twenty-five trees were treated 

 with pure kerosene emulsion, fifty with carbolineum emulsion, and twenty- 

 eight with pure carbolineum. Just previous to these treatments the trees 

 in the whole block had been pruned carefully. The material was carefully 

 brushed over the trunks, covering all the cut surfaces of the recently 

 removed branches. 



The trees were examined on June 28. The block as a whole showed 

 severe infestation, sawdust being present at the base of a great many 

 trees, and this could be seen for a long distance down the nursery row. 

 In the rows treated with carbolineum or its emulsion no sawdust could 

 be seen and the trees were growing vigorously, the trunks showing a deep 



