﻿20 BULLETIN 1128, U. S. DEPARTMENT OF AGRICULTURE. 



SAPSUCKER WOUNDS. 



Sapsuckers arc a group of woodpeckers which extract the sap 

 from the inner bark and sapwood of living trees and eat the cambium. 

 The final result after the wound has healed or callused over is the 

 so-called bird pecks (15, 35). This injury is often accompanied by 

 extensive staining, particularly in the hardwoods. On the ends of 

 logs or boards the healed wounds appear as stained areas of varying 

 size, each containing a more or less open, short, radial check in con- 

 nection with distorted grain. The general appearance is a T-shaped 

 or triangular mark or check surrounded by a stain varying from 

 brown to almost black. More than one usually occurs in the same 

 annual ring. On the edge-grain or slash-grain faces of sawed lumber 

 these injuries usually appear as small knots or distortions in the 

 grain, surrounded by more or less stain which is usually localized, 

 but the stain may be accompanied by a bleaching which extends for 

 some distance. The stain is always adjacent to the distorted grain, 

 and the more distorted the grain the greater 

 the extent of the stain. 



The stain appears to be the most injurious 

 of the two, but in reality the distorted grain 

 is the only cause of weakening in the wood. 

 The strength of the wood is not much affected, 

 so that wood with bird pecks in most cases 

 can be safely utilized. Figure 6 shows a sec- 

 tion from a white-ash longeron with a minor 

 injury of this kind which does not impair the 

 usefulness of the member. Pieces are some- 



fig. 6. — Section from a times unsuitable for handles, owing to the 

 fn n g is a ed sapsucker' injury tendency of the grain to roughen up at these 

 ash bird peck in white pl aces when planed. If the pecks are nu- 

 merous in one annual ring it is best not to 

 use the piece, for although it has not been determined by comparative 

 tests it is quite probable that such material is reduced in strength. 

 Checks or wind-shakes are very prone to occur along an annual ring 

 containing numerous sapsucker wounds or even at individual in- 

 juries. These often prove to be serious in thin veneer, since pieces of 

 the distorted grain are likely to fall out. Sapsuckers are responsible 

 for much of the curly grain and bird's-eye found in tulip poplar. 

 Both stain and bird's-eye in this species are shown in Figure ( . 



Practically all tree species, both softwoods and hardwoods, are 

 subject to this type of injury, but hard maple, soft maple (Acer sac- 

 charinum Linn.), tulip poplar, and hickory in particular stain badly. 

 The bird pecks are common in white ash, but the accompanying 

 stain is generally closety localized. 



PITH-RAY FLECKS. 



Pith-ray flecks, which are also termed medullary spots and pith 

 flecks, are caused by the larvae or grubs of certain insects living in 

 the cambium of living trees during the growing season (10, 17, 20, 

 21, 4.4., 67). These insects comprise several species of the genus 

 Agromyza belonging to the order Diptera. On the end section of 

 logs or lumber the flecks appear as small brown crescent or half-moon 



