8 CONNECTICUT EXPERIMENT STATION BULLETIN 1 55. 



EFFECT UPON THE TREES. 



It has previously been mentioned that the adult beetles do 

 more or less feeding, always eating holes entirely through the 

 leaves, as is shown on cover of this bulletin. This of course 

 injures the tree, but is much less serious than the damage 

 caused by the larvae, which eat away the under surface of the 

 leaves. The larvae are always more abundant than the adult 

 beetles, and are more voracious in their feeding habits. The 

 worst infested trees usually drop their leaves in Connecticut 

 about the middle of July. If this happens, and is followed by 

 a rainy season, new leaves will be put out, but in a season of a 

 protracted drought the trees may fail to put forth new leaves. 

 In either case the tree is undoubtedly weakened, and often seri- 

 ously so. Sometimes the second crop of leaves is devoured by the 

 second generation of beetles, but in Connecticut the white fungus 

 mentioned in another part of this bulletin is apt to serve as an 

 important check to the beetle in a wet season. Two complete 

 defoliations, one succeeding the other, usually kill a tree. 

 Usually, however, the defoliation is not quite complete, and the 

 trees continue to exist in a greatly weakened and devitalized 

 condition. In the cities and larger towns, on account of further 

 injuries* by horses, by leaky gas pipes in the ground, and pave- 

 ments which cut off the supply of moisture, many trees have 

 died. In 1901 the writer was called to Norwich, where nearly 

 every elm had died for a distance of about one and one-half 

 miles on a prominent residential street. These trees had been 

 weakened by the constant attacks of the beetle year after year, 

 and a leaky gas main finally destroyed what little vitality 

 remained. Most of the maple trees along the street survived. 



In many cases young or newly planted trees seem to be 

 especially subject to attack, and therefore should receive extra 

 attention. 



FOOD PLANTS. 



Elms constitute the only food plants known for this insect, 

 and the European species suffer more than the American ones. 

 The English elm (Ulmus campestris) and its weeping variety 



* For a discussion of these injuries the reader should consult Bulletin 

 131 of this Station. 



