REPORT OF THE DIRECTOR IQII 55 



ive barrier to its being introduced with trees and shrubs. The 

 observations above relating to the parasites of the gipsy moth apply 

 equally to the natural enemies of the brown-tail moth. 



Shade tree pests. The Entomologist investigated conditions 

 in a number of communities and found exceptionally severe and 

 widespread injury by the elm leaf beetle. The defoliation was so 

 general, in connection with the work of previous years and the 

 severe droughts of earlier seasons, that many trees have succumbed 

 or are likely to die in the immediate future unless radical measures 

 are adopted for their better protection. 



There seems to be great difficulty in securing efficient treatment, 

 even if the equipment be adequate. This defect has been pointed 

 out and, with a fuller understanding on the part of those compelled 

 to solve the problem, we look for materially better results another 

 season. The elm leaf beetle is not such a serious pest in Europe, and 

 it would seem, in view of the probable continuance of the severe 

 injury of the last few years, to be due in part at least to changed 

 conditions, as though a serious effort might well be made to secure 

 natural enemies, since they appear to be very effective checks upon 

 this beetle in European countries. 



The cottony maple scale and the false maple scale occasioned 

 repeated complaints, owing to their effect upon hard and soft maple, 

 especially in the vicinity of New York City. An unfortunate con- 

 dition developed in the city of Mount Vernon. Several hundred hard 

 or sugar maples were seriously injured or killed, following the appli- 

 cation of one of the commercial miscible oils in early spring. An 

 investigation convinced the Entomologist that the trouble was due to 

 the material applied, the injury being greatly aggravated by subse- 

 quent cold weather retarding growth and producing conditions favor- 

 able for penetration by the oil. We must therefore classify early 

 applications of oily preparations as dangerous to hard maples. 



The extended outbreak by the green maple worm was investigated 

 and must be partly charged to the general destruction of birds and a 

 consequent scarcity of the insectivorous species. Investigation^ by 

 Zoologist W. G. Van Name showed that nine species were feeding 

 upon the caterpillars, while seven others were in the vicinity, prob- 

 ably for the same purpose. A relatively slight increase in the number 

 of the birds would doubtless have prevented the defoliation of the 

 trees. The spiny elm caterpillar and the white-marked tussock moth 

 are two other shade tree pests which were excessively abundant and 

 the subjects of much correspondence. The ornamental birches are 



