INSECTS INJURIOUS TO FOREST TREES 511 



the young larva; before they make their nests if the trees are 

 sprayed as soon as the eggs are hatched in the late fall. 



Tent -caterpillars and tussock-moths, which have been de- 

 scribed in the chapter on orchard insects, and many other 

 leaf-feeding larvae, often do much damage to shade trees. A 

 study of their habits and life history will usually reveal some 

 vulnerable point and suggest the control measures to be 

 adopted. Where arsenate of lead is used it is usually necessary 

 to use 4 or 5 pounds to 50 gallons of water. 



The Elm Leaf -beetle (Galerucella luteola). Elm trees are 

 attacked and seriously injured by many different insects. In 

 many places the leaf-beetles are the most important of these 

 pests. These beetles are about one-fourth of an inch long and 

 greenish or yellowish marked with darker spots and lines. 

 They hibernate in protected places during the winter and feed 

 for awhile on the young leaves in the spring before they lay 

 their eggs. The larvae feed for two or three weeks before de- 

 scending to the ground to pupate. There may be two genera- 

 tions each year. 



Although it is difficult to spray trees as tall as elms often 

 grow to be, without the use of special apparatus, yet it is pos- 

 sible to construct a spraying outfit that will enable the operator 

 to reach easily all parts of the tree. Infested trees should be 

 sprayed with arsenate of lead as soon as the beetles begin to 

 feed in the spring, and again about two weeks later when the 

 first larvae hatch. Sometimes later sprayings may also be 

 necessary. 



Plant -lice and Scale -insects. Many of the plant-lice that 

 feed on the foliage of various shade trees, and the scale-insects 

 that may attack any parts of the trees above the ground, can 

 often be controlled by spraying with kerosene emulsion during 

 the summer or, and usually better, with the sulphur-lime wash 

 during the winter. 



The Locust-borer (Cyllene robinia). Locust trees are often 

 attacked by borers which after a little while penetrate so far 

 into the wood that they cannot be removed or killed. These 

 borers are the larvae of dark-brownish beetles which are about 

 an inch and a half long and have eight or ten narrow golden 



