130 



120 



I 10 



100 



90 



80 



70 



60 



50 



Precipitation 

 NE Washington 



Year 



Annual predpitation in the western Giscades was 

 lower ^an average most of the years between 1 985 



and I "yj. Source: Washington Department of Natural Resources. 



summer, such as shallow, hardpan or deep, 

 gravelly soils. 



Diseases or outbreaks of insects, such as 

 forest tent caterpillar on red al- 

 der in 1987, often are associated 

 with drought-stressed trees and 

 accelerate tree death. By them- 

 selves, many of these insects or 

 diseases rarely cause mortality. 



Pacific dogwood is affected 

 by fungus — Since the early 

 1970s, the native dogwood in 

 western Washington has been in- 

 fected by anthracnose, an intro- 

 duced fungus disease of foliage 

 and stems, that is often fatal af- 

 ter a few years of infection. Many 

 west-side dogwoods have suc- 

 cumbed to the disease over the 

 last 20 years. Some stands that 

 had five dogwoods per acre 20 

 years ago may have none today. 

 In other areas, the disease is not 

 as common. Dogwood under- 

 story in the eastern parts of the 

 Columbia Gorge is generally 

 healthy. 



Pacific madrone is injured by winter 

 freezes — Winter freezes periodically damage 

 tens of thousands of Pacific madrones through- 

 out the Puget Sound region. Injury ranges 

 from leaf browning to branch dieback and tree 

 mortality. Trees with only leaf browning usu- 

 ally recover. Madrone trees with winter freeze 

 damage have been noted in 1972, 1985, and 

 1990. In the spring of 1996, madrones suf- 

 fered nearly complete browning of the leaves. 

 Sometimes the leaves at the tops of the trees 

 were relatively undamaged. Often, affected 

 trees were found adjacent to completely unin- 

 jured trees. A weak parasitic fungus is sus- 

 pected of colonizing the leaves after they were 

 stressed by cold weather in January 1 996. Two 

 leaf-mining insects were also found in the in- 

 jured leaves and probably contributed to about 

 one-third of the foliage damage. Emergence 

 of normal-appearing 1996 leaves nearly hid the 

 dead leaves. Whether the fungus can persist 

 and spread to the new leaves is unknown. 



Leaf miners are one of several insects that attack Pacific 

 maidrone. 



Washington — 52 



