Most plantations with severe symptoms are 

 10 to 25 years old and within 15 miles of the 

 coast in an area prone to fog; before they were 

 logged, these areas were dominated by hem- 

 lock, spruce, and cedar. Swiss needle cast also 

 infects plantations farther inland on the west 

 side, typically where large plantings of Doug- 

 las-fir occupy valleys surrounded by hills or 

 mountains, where poor air drainage contrib- 

 utes to the buildup of the fungus. These in- 

 land plantations usually recover from heavy 

 infection after 2 to 5 years, so changing them 

 to species other than Douglas-fir is unneces- 

 sary. The disease can be controlled with fun- 

 gicides, but treatment in forest plantations is 

 uncommon and not usually advised. 



Hemlock 



Two dwarf mistletoes infect hemlock 

 trees — ^Western hemlock dwarf mistletoe is 

 the most widespread dwarf mistletoe in west- 

 ern Washington. Taxonomically, this para- 

 sitic plant is separated into two subspecies 

 that look almost identical but are specific to 

 the two species of hemlock found in west- 

 ern Washington: western hemlock and 

 mountain hemlock. Each subspecies also 

 infects a variety of true firs, spruces, and 

 pines to a much lesser extent than hemlock. 

 Western hemlock dwarf mistletoe is a seri- 

 ous parasite along the Pacific coast from 

 California north to Glacier Bay, Alaska. As 

 with all dwarf mistletoes, infected trees show 

 increased raiortality, reduced growth, lower 

 fiber quality, and an increased susceptibil- 

 ity to other disturbance agents. Heavily in- 

 fected trees show growth reduction in both 

 volume (40%) and height (84%) compared to 

 uninfected or lightly infected trees. 



Mountain hemlock dwarf mistletoe is com- 

 mon on mountain hemlock and true firs in 

 northern California and the Oregon Cas- 

 cades but, until recently, was thought to be 

 restricted to small populations in two areas 

 in Washington — north of Mount Baker and 

 in the southern Olympic Mountains. Surveys 

 conducted in 1995 in the Washington Cas- 

 cades discovered at least three new, widely 

 separated populations of this parasite. 



Hemlock infected by dwarf mistletoe is deformed, 

 grows less, and is often killed. The large tree on 

 the left is heavily infected with many mistletoe 

 "brooms" (excessive branch growth caused by 

 the infection). 



Western hemlock looper is a pest of old 

 growth — The primary host for hemlock looper 

 is western hemlock, although it will feed on 

 other conifer species and understory shrubs 

 found in association with western hemlock. 

 Heavy, repeated defoliation during an outbreak 

 can result in tree mortality. 



Western hemlock looper is generally very 

 successful in extensive, old -growth, western 

 hemlock forests. Early records of western 

 hemlock looper outbreaks show vast 

 amounts of timber killed in northwest Or- 

 egon and southwest Washington. Outbreaks 

 generally last about 3 years and are usually 

 brought under control by the natural action 

 of parasites, predators, and disease. Out- 



Washington— 49 



