2 INSECT INJURIES TO WOOD OF DYING AND DEAD TREES. 



damaged to a somewhat less extent, but instances are known in which 

 more than one billion feet of storm-felled timber within limited areas 

 were reduced in value 25 to 35 per cent within three months after the 

 storm. The fire-killed and insect-killed sugar pine, silver pine, and 

 yellow pine of the western forests are also damaged in a similar man- 

 ner and the value of the product greatly reduced within a few months 

 after the trees die. The aggregate losses from this secondary source 

 in the coniferous forests of the entire country contribute largely to the 

 annual waste of millions of dollars' worth of forest products which 

 otherwise might be utilized. 



Amhrosia heetles. — Wood-boring insects of another class, known as 

 timber beetles or ambrosia beetles, cause pinhole defects, principally 

 in the sapwood, although some of them extend their burrows into the 

 heartwood. These insects make their attack in the early stage of the 

 declining or dying of the tree, or before the sapwood has materially 

 changed from the normal health}'' condition, and often in such num- 

 bers as to perforate everj^ square inch of wood. Thus the wood is 

 not only rendered defective on account of the presence of pinholes, 

 but the holes give entrance to a wood-staining fungus which causes a 

 rapid discoloration and produces still further deterioration of the 

 product. 



The sapwood of trees dying from the attack of other insects or 

 from fire, storm, or other causes is often reduced in value 50 per cent 

 or more, and in some cases the value of the heartwood is reduced in a 

 like manner from 5 to 10 per cent. 



Pinhole horers in cypress. — An example of the destructive work 

 of insects which attack dying and dead trees is found in the cypress 

 in the Gulf States, where these trees are deadened by the lumbermen 

 and left standing several months, or until the timber is sufficiently 

 dry to be floated. Upon investigation it was found that trees dead- 

 ened at certain seasons of the year were attacked by the ambrosia 

 beetles, or pinhole borers, and that in some cases millions of feet of 

 timber had been reduced 10 to 25 per cent or more in value.*' 



HARDWOOD TREES. 



Roundheaded horers, timber worms, and ambrosia beetles. — The 

 principal damage to dying and dead hardwood trees is caused by cer- 

 tain roundheaded wood-borers (Cerambycidae) with habits similar to 

 the sawj^er, by the timber worms mentioned as damaging living tim- 

 ber, and by ambrosia beetles having habits similar to those that attack 

 the sapwood and heartwood of conifers. All of the hardwoods suffer 

 more or less, but. the greatest damage is done to the wood of hickory, 



« For methods of preventing pinhole injury to girdled cypress see Circular No. 

 82 of the Bureau of Entomology, U. S. Department of Agriculture. 

 [Cir. 127] 



