SITKA SPRUCE '. USES, GROWTH, MANAGEMENT. 21 



Forest in southeastern Alaska were defoliated by the combined activ- 

 ity of sawfly larva? and caterpillars belonging to the Tineid family. 

 Thus far only a small portion of the Sitka spruce in southeastern 

 Alaska has been killed by this widespread defoliation. 



Occasionally aphids kill the foliage of Sitka spruce. The western 

 spruce gall louse (Aphis abietina) is believed by Dr. A. D. Hop- 

 kins of the Bureau of Entomology to be the aphid which caused 

 the loss of the needles of Sitka spruce over thousands of acres of 

 forest in 1918 in various portions of the coast region in Oregon 

 and Washington. Fortunately the activity of this aphid was of 

 extremely short duration, and only about 15 per cent of the in- 

 fested spruce was killed. Most of this loss was confined to swamp 

 and tideland areas in the lower Columbia River basin and the 

 coast region and included only the poorer stands of timber. The 

 Sitka spruce gall aphid (Chermes cooleyi) is found very commonly 

 doing injury to Sitka spruce reproduction and occasionally causing 

 its death. Large trees also are attacked, but the injury to them 

 is rarely severe. These minute insects cause the development of 

 conelike galls which kill the affected twigs. Infested trees of special 

 value, such as those in parks and streets, may often, with good results, 

 be sprayed with contact sprays like kerosene emulsion. 



Fortunately the work of defoliators does not continue more than 

 a few years when it is Controlled by natural agencies. Under forest 

 conditions control measures against this class of insects are not 

 feasible. However, defoliators greatly increase the fire hazard on 

 the areas on which they have been active. Nearly always the fires 

 which followed the defoliators did more damage than the insects 

 themselves. The reduction of the fire risk on the defoliated areas 

 is. therefore, an important consideration in defoliator problems. 



Felled timber of Sitka spruce is subject to the attacks of various 

 wood borers. Logs cut between April and September are frequently 

 attacked, shortly after being felled, by ambrosia beetles, sometimes 

 called timber beetles or pinhole borers. These are small, elongate, 

 wood-boring beetles which excavate round black tunnels, the di- 

 ameter of a pencil lead, into the wood of dying trees and stumps, 

 ell as logs. Investigations by the Bureau of Entomology in 

 1919 showed that species of Griathothrichus and Xyloterus commonly 

 attack' Sitka spruce logs, as well as western hemlock and Douglas 

 fir. These borers may penetrate the wood (o a depth of from 4 

 to 6 inches and therefore seriously reduce the value of the sapwood. 



especially when Sitka spruce is being used for such special pur- 



posei as airplane stock-. The logs which are cut in (lie late fall ami 

 winter are usually attacked in the following spring. Logs cut in 

 the early fall are not entered that season: and, if piled loosely in 



