180 MISC. PUBLICATION 273, U.S. DEPT. OF AGRICULTURE 



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

 felled by wind, snow, or cutting, 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 cambium layer and then penetrate the wood. Fresh, unsea- 

 soned wood still containing sap, pitch, or other essential food ele- 

 ments is required 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 care- 

 fully 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 cut- 

 ting at the proper season, prompt removal of logs, poles, and other 

 unseasoned products 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 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 (34). Better 

 results may be had by thoroughly covering logs with a fuel-oil 

 solution of benzene hexachloride containing 0.4 percent by weight 

 of the gamma isomer. This treatment should give protection for 2 

 to 4 months. In cases where logs have been attacked, the insects 

 can be killed by spraying with crude orthodichlorobeneze at full 

 strength or paradichlorobenzene dissolved in 3 parts, by weight, 

 of kerosene (137). All such treatments, however, give only a 

 temporary immunity. More specific methods are discussed for 

 each of the different insect groups. 



