14 



BULLETIN 1490, TJ. S. DEPARTMENT OF AGRICULTURE 



PINHOLES IX LIVIXG TKEES CAUSED BY TIMBER WORMS 



Pinholes or wormholes in the heartwood of chestnut and red oak, 

 one one-hundredth to one-fourth of an inch in diameter, open, clear, 

 not stained, but lined with a substance about the color of the wood, a 

 large number of holes in a given space, are made by timber worms 

 hatching from eggs laid in or near scars. The holes made by the 

 grubs are not of uniform size ; they may extend several feet through 

 the wood. (Fig. 15.) 



This defect, due to the chestnut timber worm, 4 is one of the most 

 common and serious defects in chestnut timber throughout its range. 

 It is rare to find chestnut trees, logs, or telephone or telegraph poles 

 free from this defect, and practically every tree of merchantable 



size is more or less affected. 





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There is a very low percentage 

 of " clear " chestnut, the re- 

 mainder being " wormy " and 

 reduced to the lower grades. 

 This defect is a " sound wormy " 

 injury and can not be pre- 

 vented. Unfortunately the chest- 

 nut is rapidly becoming extinct 

 as a commercial tree, owing to 

 the chestnut blight fungus. 



Wormy chestnut and oak wood 

 can be used wherever structural 

 strength is not necessary. They 

 are especially suitable as the 

 base for veneer in manufactur- 

 ing pianos, caskets, coffins, auto- 

 mobile running boards, and the 

 lower grades of building lum- 

 ber, because of the comparatively 

 reasonable price at which this 

 grade of lumber can be bought. 

 Much timber that would other- 

 wise be wasted can be thus uti- 

 lized. There is, however, a limit 

 to the size of the holes ad- 

 mitted. 



Similar pinholes or wormholes one one-hundredth to one-eighth of 

 an inch in diameter in oak timber (fig. 16) are caused by the oak 

 timber worm. 5 This defect is especially serious in large mature 

 white oak trees. The holes occur in large numbers in a given space 

 and extend in all directions through the solid heartwood. This 

 insect usually affects the wood of the finest old, mature, or over- 

 mature trees, sometimes causing defects which result in the discard- 

 ing of entire trees for such uses as tight barrel staves. This defect is 

 classified under the term " wormholes, no living worms or decay," 

 and can not be prevented when occurring in living trees, although 

 losses can be lessened by clean forest management ; that is, removal 



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Fig. 15. — Holes cau-ed by the chestnut 

 timber worm (Melittomma sericeum), 

 which causes the defect classed in the 

 grade " sound wormy chestnut " 



HeUttomma sericeum Harris. 



Eupsalis minuta Drury 



