INSECTS AND DISEASES THAT DESTROY FORESTS 65 



the leaves and thus remove an important means 

 which the tree has of getting food and drink. 

 Wire worms attack the roots of the tree. Leaf 

 hoppers suck on the sap supply of the leaves. 

 Leaf rollers cause the leaves to curl up and die. 

 Trees injured by fire fall easy prey before the 

 attacks of forest insects. It takes a healthy, 

 sturdy tree to escape injury by these pirates of 

 the forests. There are more than five hundred 

 insects that attack oak trees and at least two hun- 

 dred and fifty different species that carry on de- 

 struction among the pines. 



Insect pests have worked so actively that 

 many forests have lost practically all their best 

 trees of certain species. Quantities of the largest 

 spruce trees in the Adirondacks have been killed 

 off by bark beetles. The saw-fly worm has killed 

 off most of the mature larches in these eastern 

 forests. As they travel over the National and 

 State Forests, the rangers are always on the 

 watch for signs of tree infection. Whenever 

 they notice red-brown masses of pitch and saw- 

 dust on the bark of the trees, they know that 

 insects are busy there. Where the needles of a 

 pine or spruce turn yellow or red, the presence of 

 bark beetles is shown. Signs of pitch on the bark 



