INSECT ENEMIES OF WESTERN FOKESTS ][4X 



INSECTS INJURIOUS TO WOOD AND FOREST 

 PRODUCTS 



Insects lay a heavy toll on crude and finished forest products {"26^ 

 Ifl^ 72^ 76)^ a loss that has been variously estimated to be from 1 

 to 5 percent of the annual cut. The principal damage to forest 

 products is caused by insects that feed on or bore into the wood. 

 Some damage is done to wood while still in living trees, but a great 

 deal occurs after trees have been killed or felled, and before utihza- 

 tion; and the green or seasoned lumber, and even the final utilized 

 products are fed on by insects. 



After a tree has been killed by fire, insects, or other causes, or 

 felled by w^ind, snow, or cutting operations, it becomes particularly 

 attractive to a large variety of insects. Ambrosia beetles find the 

 dying wood with fermenting sap an especially suitable medium for 

 the growth of their fungi. Horntail wasps, or wood wasps, settle on 

 freshly felled trees, sometimes before the woodsmen have finished 

 cutting them into logs, and on fire-killed trees before the fire is out, 

 and insert their long slender ovipositors deeply into the wood to lay 

 their eggs. Many of the flatheaded and roundheaded borers, 

 weevils, and larvae of carpenter moths and clear-winged moths are 

 wood boring in habit. The larvae usually feed for a time in the cam- 

 bium layer and then penetrate the wood. Fresh, unseasoned w^ood 

 still containing sap, pitch, or other essential food elements is re- 

 quired for them. In short, so many different species of wood-boring 

 insects start their work on killed or felled trees that it is important 

 that such timber be peeled or promptly removed from the woods 

 to avoid heavy damage. 



After lumber has been kiln dried it becomes reasonably safe from 

 insect attack. There are, however, a few important groups which 

 still persist in their attacks unless the wood is properly handled. 

 The seasoned sapwood of hardwoods is particularly susceptible to 

 damage by powder-post beetles and must be carefully managed in 

 the lumber yard or in storage to avoid becoming infested. Even 

 after timbers are in place they are subject to attack by these insects, 

 by carpenter ants, by certain roundheaded wood borers, flatheaded 

 borers, and by termites unless precautions are taken to provide 

 proper insulation from the ground or protection is secured through 

 the impregnation of the wood with creosote or other chemicals. 



As has been indicated, the control of insects injurious to forest 

 products is largely a matter of prevention of damage through cutting 

 at the proper season, prompt removal of logs, poles, and stulls from 

 the woods, proper handling in the mills, and certain precautions in 

 utilization. Logs that are to be used for poles or in rustic work 

 should be peeled before wood borers have had an opportunity to enter 

 the wood. Some success has been obtained in repelling attacks of 

 wood borers by spraying logs with coal-tar creosote diluted with 3 

 parts of kerosene {23). In cases where logs have been attacked, the 

 insects can be killed by spraying with crude orthodichlorobenzene at 

 full strength or paradichlorobenzene dissolved in 3 parts, by weight, 

 of kerosene {72). All such treatments, however, give only a tem- 

 porary immunity. More specific methods are discussed for each of 

 the different insect groups. 



