PARCH BLIGHT ON DOUGLAS FIR IN THE PACIFIC 



NORTHWEST 



THORNTON T. HUNGER 

 Forest Service, Portland, Oregon 



Quite frequently in the spring of the year the foliage of the 

 Douglas fir trees in the vicinity of Portland, Oregon, turns 

 brown. In March and April entire trees are sometimes as sere 

 as though they had died recently, and groves look from a distance 

 as though a hot fire had scorched them. The injury is sometimes 

 so striking as to give rise to the impression that all the timber 

 is dying. But with the beginning of the growing season most of 

 the buds open normally and by midsummer the trees have re- 

 gained their usual green appearance. Close examination in mid- 

 summer indicates that many of the old needles are brown and 

 are dropping off, and that in places the one-year-old twigs have 

 been killed. 



The injury is most serious on isolated, exposed trees, on the 

 eastern sides of these trees, and on the eastern edges of groves. 

 Trees on the western side of dense groves show almost no signs 

 of the injury. Trees of all ages apparently are equally affected. 

 It is also noticeable that timber on exposed hillsides facing the 

 east is more subject to injury than that in protected locations. 

 Some of the species associated with Douglas fir are also browned, 

 but to a less degree. 



For several springs there has been some evidence of 'Hhe 

 blight" in the vicinity of Portland, but it was particularly notice- 

 able in 1913 and 1915. 



The cause for the blight is rather easy of explanation, but 

 none the less interesting to the plant physiologist and to the 

 forester. It is due to the drying east winds — the Chinook 

 winds — that occasionally sweep across the Cascade Mountains 

 from the interior plateau country and parch the Douglas firs, 



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