DEFECTS IN TIMBER CAUSED BY INSECTS 



15 



of old dead and dying snags, stag-headed trees, and trees badly fire- 

 scarred. From 20 to 25 per cent of oak lumber may be wormy from 

 this cause. A loss of 15 to 20 per cent of the product is 

 considered low. 



Pinholes or wormholes one-eighth to three-sixteenths of an inch in 

 diameter, few to many grouped in a given space, accompanied by a 

 staining of the wood, or all more or less connected by irregular 

 blackened streaks, 



in 



oak, maple, tupelo gum, 

 beech, and other hard- 

 woods, are similar to 

 those caused by the 

 oak timber worm. This 

 defect is caused by 

 tenebrionid timber 

 worms. 6 The insect 

 lays its eggs in the 

 living tree near a scar 

 or wound, and many 

 larvae working to- 

 gether excavate irregu- 

 lar cavities and longi- 

 tudinal burrows some- 

 times a foot in length. 

 This defect is fairly 

 common throughout 

 Pennsylvania, Mary- 

 land, and Virginia and 

 is classed as " worm- 



!f e-junit! 



' a ; • i i if. f h f 3 c. ! 



ill I f ;fli 



ill's,,,, 



iiiliilj 



it 





III Pill 



1 1 .* I: 



Fig. 16. — Pinholes caused by the oak timber worm 

 (Eupsalis minuta), which causes the defect classed in 

 the grade " sound wormy oak " 



classed 

 holes, no living worms 

 or decay." Although 

 the losses can be greatly lessened by clean forest management, 

 they are not preventable from the lumberman's standpoint. 



PINHOLE DEFECTS FORMED IN WOOD AFTER THE TREES ARE FELLED; A 



PREVENTABLE LOSS 



Pinholes in felled timber are similar to those caused in living trees 

 by ambrosia beetles and timber worms. Such holes are less than 

 one-eighth of an inch in diameter and open, either darkly stained or 

 unstained, or with dark streaks in the surrounding wood. 



PINHOLES IX FELLED TREE" CAUSED BY AMBROSIA BEETLES 



In sapwood or heartwood of white oak, chestnut, yellow poplar, 7 

 birch, beech, and sweet gum the pinholes caused by ambrosia beetles 

 are about one-twelfth of an inch in diameter, open, usually isolated, 

 and always accompanied by long, discolored streaks in the surround- 

 ing wood. Lumber with such defects is rejected for the higher 



grades. 



6 Strongylium spp. 



7 The adult of Corthylus columbianus Hopkins causes pinholes in hardwoods with which 

 discolored streaks are associated. 



