SHADE TREE PESTS 



45 



form layers nearly half an inch deep. In such places they change to 

 beetles in five or more days. Up to 1894 this was supposed to complete 

 the life history of the insect in this latitude, but that year the late 

 Dr Lintner discovered the presence of a second brood and subsequent 

 observations have not only demonstrated this to be the rule but that 

 under exceptional circumstances there may even be a partial third 

 generation. The grubs of the second generation are destructive in 

 August. The development of the first brood is governed to some 

 extent by local conditions, and later in the summer there is considerable 

 diversity even on trees of the same street. The bulk of the larvae may 

 be pupating under some elms, while on others numerous eggs and young 

 may be found. The various stages of this insect are passed so rapidly 

 that close observation and a ready adaptation to conditions are necessary 

 in attempting to control it. 



Remedies. Since the beetles fly into the trees each spring, the 

 application of bands of any substance around the trunk will not have the 

 slightest effect in preventing attack. A band is of value only when it 

 keeps an insect not already in the tree from ascending the trunk. 

 "Sticky fly paper has been placed around trees attacked by elm leal 

 beetles and many of the descending grubs were captured, but the 

 number killed is but a drop in the bucket compared with the host that 

 transform in safety above. The grubs may also be killed in large 

 numbers as they lie in masses around the trunk. But even this can be 

 considered as but a palliative measure, for a considerable proportion 

 must escape, and as the beetles are so prolific (one may deposit over 600 

 eggs), it requires comparatively few to cause serious injury. Another 

 so called remedy is plugging the afflicted trees with sulfur or other 

 compound. The idea being to introduce into the trunk, where it will be 

 taken up by the sap, some substance which will not injure the tree and 

 yet kill the insects, or at least render the foliage distasteful to them. It 

 is a plausible theory but has no foundation in fact. The only thoroughly 

 satisfactory treatment for this insect is found in spraying the foliage with 

 some arsenical compound. The method of doing this will be treated of 

 more fully on following pages. 



