174 THE APPLE 



increases considerably in size the second year and does not feed 

 exclusively on the sapwood, but gnaws into the heartwood. The 

 winter of the second year is passed deep in the burrows. The third 

 year the borer penetrates still deeper into the heart of the tree, 

 there reaching a full larval development. It finally forces its way 

 back to the bark and forms a pupa, from which it emerges the 

 following spring as the adult beetle. 



Appearance of infested trees. The presence of the round-headed 

 borer is usually not detected until the second year. It may be rec- 

 ognized by the discolored, sunken patches of bark marking the 

 burrows beneath. These areas sometimes show an exudation of 

 sap from the wound, but more often are evident by the castings 

 thrust out by the larva. The area of egg-laying is usually in the 

 trunk, within a foot or two of the ground, but in small trees it is 

 often found below ground, at the crown. Several larvae may girdle 

 and destroy a young tree. In older trees the injury is not always 

 fatal, but the growth of both tree and fruit is heavily retarded. 



Remedies. The borers are readily removed by a knife, or killed 

 by a prodding of their channels with a sharp wire. When there 

 are several borers in one tree the use of a knife is not altogether 

 safe because of the danger of girdling the trunk. The safest, 

 surest method is to tap the channels and inject into them small 

 quantities of bisulphide of carbon, stopping up all entrances to the 

 channels with wax, or something similar, to prevent the escape of 

 the gas. The deadly fumes of carbon bisulphide penetrate to all 

 parts of the tunnels and kill the larvae within, making it unnecessary 

 to cut into the bark or wood in search of them. 



Shot-hole borer. The shot-hole borer usually works in the 

 branches of the tree. So far as observed, it has not yet done a 

 great deal of damage to the apple trees in the Eastern states. In 

 any event, it is injurious only when a tree is greatly reduced in 

 vitality from some other cause, and the remedy is to increase the 

 vigor of the tree. 



Lice, or Aphids 



Oyster-shell scale. Three scale insects commonly occur in our 

 apple orchards. The scurfy scale is found in almost every orchard, 

 but seldom in very large numbers. The oyster-shell scale, or 



