6o PRACTICAL TREE REPAIR 



forth in June and all infested wood should be 

 burned before that time. Excision is practicable 

 during the early stages of the attack. Preventive 

 dressings should be put on the trees late in May 

 and kept on for two months. A close relative of 

 the birch borer, the sinuate pear borer, is destruc- 

 tive in some eastern states. 



Another flat-head, the two-lined chestnut borer, 

 is effectively helping the chestnut bark disease to 

 kill out the American chestnut. The beetle is 

 black, with two faint lines on its back, and per- 

 haps three-eighths of an inch long. The larva 

 is twice as long, and white, with a touch of brown 

 at each end. The mature insects appear in May 

 and June. Infested wood must be barked (and 

 the bark burned) by the first of April. 



Insects which burrow simply in the wood of the 

 tree, not consuming any large part of cambium, 

 are not nearly so damaging to the tree as most of 

 the bark borers. Only a few species are likely to 

 be the objects of genuine campaigns. Many of 

 them, however, come to notice rather often in the 

 work of tree repair because of their presence in 

 decayed trees. Typical of the whole tribe is the 

 flat-headed apple borer. Its larva, remarkable 

 for its disproportionately large head, bores ir- 

 regular mines in the sapwood of the apple and 

 many other deciduous trees. The eggs are laid 

 in June or July, and the insect is not so small but 



