EMORY OAK IN SOUTHERN ARIZONA. 11 



INSECTS. 



Observations indicate that the wood and bark boring insects do 

 considerable damage. In certain stands as much as 95 per cent 

 show the borings from the base to near the top of the tree. The 

 openings in the boles and branches seem to give entrance to wood- 

 decaying fungi. 



WIND. 



Windshake is prevalent, affecting one-eighth of the trees in even 

 the most sheltered stands, and as much as three-fourths in the most 

 exposed. Combined with the beetle galleries, the shake adds greatly 

 to the liability to severe heart rot. 



GRAZING. 



In the spring, when the range grasses are not available, cattle and 

 horses browse on Emory and other oaks, mesquite, acacia, and other 

 woody growth. Where this growth is limited and there is much 

 stock the young oak sprouts may suffer considerably, and some stools 

 may be killed outright as the result of grazing, though such severe 

 injury is uncommon. Indeed, browsing may have a beneficial effect 

 as a form of pruning early in the dry season, and certainly the ever- 

 green oaks are an important asset to the grazing industry in helping 

 to carry the stock over to the rainy season. 



FUNGI AND MISTLETOE. 1 



The heartwood of living trees of the Emory oak is attacked by a 

 number of species of fungi. Polyporus dryopMlus Berk, frequently 

 causes a brown and white mottled rot, commonly known as the piped 

 rot; next in frequency of occurrence is Fomes everJiartii (Ellis and 

 Gall.), which causes a whitish rot varying to brown on the outer 

 edges; Polyporus sulphureus (Bull.) Fr. occurs occasionally, pro- 

 ducing a brown, coarsely checked rot; Polyporus obtusus Berk, and 

 Hydnum erinaceus Bull, cause whitish rots of less frequency. 



The wood of dead trees and timbers of oaks of this species are 

 attacked by a number of species of fungi, which as a rule attack first 

 the sapwood and later may rot the heartwood. Ganoderma cortissii 

 (Berk.) Murr. causes a whitish, stringy rot of the butts of dead trees 

 and stumps; Polyporus gilvus (Schw.) Fr. is found attacking the 

 sapwood of defective living trees, as well as that of dead trees and 

 logs; Polyporus adustus (Willd.) Fr., Polystictus versicolor (L.) Fr. ; 

 Polystictus sanguineus (Mey.) Fr., and Stereum spp. are also common 

 causes of decay in dead oak trees and timbers of this species. 



Contributed by Dr. George G. Hedgcock, Office of Investigations in Forest Pathology, Bureau of 

 Plant Industry. 



