Annosus root disease has also increased in 

 distribution and severity as a result of man- 

 agement practices. Selective logging creates 

 abundant stumps of ponderosa pine, grand fir, 

 and subalpine fir that can be infected by air- 

 borne spores. This increase in infection sites 

 is compounded by high tree densities that in- 

 crease the probability of tree-to-tree spread 

 through root contact. Annosus root disease 

 is particularly common in mixed stands of true 

 fir and Douglas-fir of the southern Cascades 

 near Yakima and Goldendale. 



Eastern Washington has areas with large 

 amounts of schweinitzii root and butt rot in 

 late serai and climax stands. The primary host 

 is Douglas-fir, but western larch, spruce, and 

 true fir are also infected. Infected trees rarely 



The fungus that causes armillaria root 

 disease often produces edible mushrooms 

 at the base of infected trees. 



Armillaria root disease. Incidence of 

 armillaria root disease is also on the rise 

 in the expanding Douglas-fir /grand fv 

 timber type: mortality has increased 

 because of stress fi-om overstocking. The 

 disease is severe on Douglasfir and 

 grand fir in northeastern Washington. 

 Armillaria is sometimes extremely ag- 

 gressive and attacks trees that do not 

 appear to be under stress, such as 

 ponderosa pine in pure pine stands 

 southeast of Mount Adams. 



show outward signs of infection. The best way 

 to detect the root rot is to find the large, rusty 

 brown and often velvety, mushroom-like fruit- 

 ing bodies on the ground near infected trees. 

 Infected wood is stained red in Douglas-fir, and 

 the advanced decay breaks down in reddish- 

 brown cubes. As in other root diseases, infec- 

 tion usually starts in root tips rather than 

 through old fire scars or wounds, as was once 

 thought. Trees with extensive butt decay may 

 attract bark beetles and even armillaria root 

 disease. 



Western spruce budworm damage is de- 

 clining — Western spruce budworm is a com- 

 mon defoliator of Douglas-fir and true fir in the 

 Pacific Northwest, and outbreaks are frequent 

 in mixed-conifer stands. Repeatedly defoliated 

 trees show substantial radial-growth reduc- 

 tion, £ind are often predisposed to attack by 

 bark beetles. Effective fire prevention and sup- 

 pression during this century have eliminated 

 many major fires and nearly all surface fires. 

 As a result, forests that have had no other dis- 

 turbances, such as timber harvesting, have 

 moved steadily toward climax and, conse- 

 quently, an abundant and expanding source 

 of the insect's favorite food — shade-tolerant, 

 late-successional tree species. 



Western spruce budworm larvae prefer new 

 foliage, but also feed on older foliage when new 

 foliage is in short supply. 



Washington — 54 



