INSECTS IXJURIOFS TO SHADE TREES. 85 



Fig. 35. Work of the hickory bark beetle. 



Remedial Measures. 



Where a slight infestation is noticed on a tolerably healthy 

 tree, the tree should be stimulated by means of appropriate 

 fertilizers (see page 25), and the trunk kept 

 covered by whitewash to which Paris green has 

 been added. Strong whale-oil soap suds will 

 answer the same purpose. If a tree is seriously infested, it 

 should be cut down at once and burned, as it is certain to 

 die in a short time anyhow and is only a menace to surround- 

 ing trees. 



PLANT LICE. 



Most of our shade trees suffer from plant lice to a greater 

 or less extent, and none more than the Norway maples. 

 These insects multiply very rapidly, suck the juices of the 



