INSECT INJURIES TO HARDWOOD EOREST TREES. 



321 



chestnut trees on thousands of square miles have died, and in other 

 sections the oaks have died to an alarming extent. 



Upon investigation in different sections of the country it was found 

 that the oak-destroying bark-borer, or two-lined chestnut borer 

 (Ayrthi* !><r< nti<ix \Veb.), is directly associated with the causes of the 

 death of the trees. 



The adult of this destructive enemy of the oak and chestnut is a 

 slender blue-black beetle with a faint yellow line along the middle of 

 each wing cover. The larva is a long, slender, flat-headed grub, which, 

 upon hatching from the egg deposited in the outer bark, burrows in 

 the inner bark, through which it extends long tortuous or zigzag 

 mines (PL XXXIX. tig. 1). When it occurs in numbers in a tree the 

 inner bark is killed and the tree rapidly dies. The leaves first fade, 

 and then dry up and re- 

 main on the twigs for 

 some weeks or months 

 afterwards. The insect 

 passes the winter in the 

 larval stage in the outer 

 portion of the inner bark, 

 where in the spring it 

 transforms to the adult. 

 The beetles commence to 

 emerge in May and June. 

 They deposit their eggs 

 in the outer bark of liv- 

 ing trees, on stumps of 

 recently felled oak and 

 chestnut, in trees struck 

 by lightning or injured 

 from other causes. They 

 breed in great numbers in the bark of stumps and injured trees, and 

 by this means are enabled to multiply sufficiently to attack and kill 

 living trees. 



METHODS OF CONTROL. 



There is evidently only a single generation of this insect annually, 

 and this fact, together with its habit of breeding in the bark of stumps 

 and injured trees, and in those killed by it, together with its habit of 

 transforming in the outer bark, suggests a practical method of control. 

 All infested stumps and dying and recently dead trees should be located 

 before the beginning of winter, or by the 1st of November, in order 

 that the infested bark ma} 7 be removed from the trunks and stumps 

 and burned before the 1st of April. 



Yees struck by lightning in May and June furnish favorable 



FIG. 33. Brood galleries of the ash bark-beetle in surface 

 of ash wood. (Original. ) 



