PEAR AND QUINCE INSECTS 231 



sapwood. The partly grown larva rests in its burrow during 

 the first winter and the next spring continues its destructive 

 work. The burrows are now much larger and more winding ; 

 they frequently intersect, cut off the supply of sap and kill 

 the branch or tree. The course of the burrows is now indi- 

 cated exteriorly by the discolored and abnormal bark above 

 them (Fig. 210). In smooth-barked trees these winding trails 

 become very conspicuous. In September of the second year 

 the larva, which is now about IJ inches in length, burrows 

 into the solid wood and there at the depth of about } inch con- 

 structs a pupal chamber which it connects with the bark by 

 an exit hole. It then plugs both ends of the chamber with 

 sawdust, becomes shorter and thicker, and the following April 

 transforms to a pupa. The beetles emerge about a month 

 later. 



Trees of all sizes from nursery stock up are subject to attack. 

 Smaller trees are frequently completely girdled by the inter- 

 secting burrows and killed outright. Larger trees are so weak- 

 ened by the presence of the borers that they soon present a 

 sickly appearance, lose their leaves and finally die. The 

 Kieffer is less subject to injury than other varieties because of 

 its greater vitality, whereby it is able to fill up the burrows with 

 new tissue. 



Treatment. 



Infested nursery stock and all other trees too badly infested 

 to be of value should be removed and burned. In many cases 

 the pupal chamber can be located by a discolored area in the 

 bark and the insect dug out with a knife. Attempts to keep the 

 beetles from emerging by coating the bark with a viscid wash 

 have not been successful, but it is probable that deterrent 

 washes, as suggested for the Round-headed Apple Tree Borer, 

 would be of some value in preventing oviposition. Several 

 applications should b(^ made during the last part of May and 

 early June, taking care to cover the larger branches as well as 



