INJURIES TO APPEARANCE OF TREES. 



19 



finally covered by wood and bark. Until this process is completed, 

 the tree is disfigured by pits with dead bark and wood at the bottom, 

 and even when completely healed, the spot remains a source of weak- 

 ness. In fact, all sapsucker pecking is followed by more or less 

 rotting and consequent weakening of the wood, and renders trees 

 more liable to be broken by the wind or other causes. 



Sapsucker injuries usually stimulate growth of the wood layers at 

 the points attacked, so that they become much thicker than usual. 

 This results in a slight swelling of the bark, and when the birds reopen 

 the old wounds year after year, as they habitually do, succeeding 

 wood layers make excess growth and in 

 time shelflike girdles develop. On trees 

 having thin, flexible, rapidly growing 

 bark, the swollen girdles are. smoothly 

 covered and rounded (fig. 5; PI. IV, fig. 

 3), but on trees having thick, brittle, or 

 stiff bark, the bark breaks and a gaping 

 furrow is formed at the summit of the 

 swelling (PI. VII, figs. 2 and 3; PI. VIII, 

 fig. 1; PI. IX, fig. 2; PI. X, fig. 1). Some 

 trees are remarkably deformed by such 

 protruding girdles (fig. 5.) 



Buds are apt to start from the edges 

 of holes drilled by sapsuckers and form 

 twigs or small branches. Such shoots 

 have been noted on honey locusts and 

 sycamores, and in some trees, such as 

 willows and elms, which are prone to 

 produce adventitious buds, they arise 

 from sapsucker injuries in such numbers 

 as to materially disfigure the trees. 



The bark may be otherwise disfigured, 

 as by exudations of gum or by pitch 

 streams, or sapsucker injury may be fol- 

 lowed by fungus attack, as in certain 



pines. Spores of Peridermium cerebrum sometimes reach the wood 

 through sapsucker punctures and cause knotty gall-like outgrowths 

 which greatly disfigure the trees. 



The wood also is often distorted and discolored in such a way as to 

 destroy its commercial value. This phase of damage by sapsuckers 

 is exceedingly important and will be made the subject of a separate 

 section of the bulletin. 



Fig. 5. — Sapsucker work on honey locust 

 (Gleditsia triacanthos). Protruding gir- 

 dles. Specimen is J 



inches in diameter. 



