Western pine beetle kills 

 big, old, ponderosa pine — 



Western pine beetle some- 

 times attacks ponderosa pine 

 in the Pacific Northwest. Nor- 

 mally, this beetle breeds in 

 large, old trees; in windfalls; in 

 trees infected by root disease; 

 or in trees weakened by 

 drought, overstocking, or fires. 

 Losses are significant because 

 large, old pines are under-rep- 

 resented across the forested 

 landscape in many areas in 

 eastern Washington. Western 

 pine beetle also attacks and 

 kills trees of all ages that have 

 bark sufficiently thick to pro- 

 tect the insect during develop- 

 ment. 



Aspen 

 Satin moth and moisture 

 stress are killing many 

 aspen stands — ^Defoliation by 

 satin moth has killed many aspen stands in 

 north-central and northeastern Washington, the late 1920s 

 Affected stands tend to be older than unaf- logical control 



Large, old, ponderosa pine, im- 

 portant for their ecological and 

 scenic value, are being killed by 

 bark beetles in overstocked 

 stands, especially in dry years. 



fected ones and apparently 

 unable to withstand insect de- 

 foliation. Moisture stress was 

 likely a factor in the mortality. 

 The defoliated stands were iso- 

 lated from other hardwood 

 stands and do not have many 

 predators or parasites to keep 

 the satin moth populations in 

 check. 



Satin moth, introduced 

 from Europe, was first found 

 in North America in 1920, 

 both in New England and in 

 southwestern British Colum- 

 bia. In the West, it has spread 

 southward to northern Cali- 

 fornia, and into the interior of 

 Oregon, Washington, and 

 southern British Columbia. 

 After its introduction into Brit- 

 ish Columbia, the satin moth 

 was considered a pest of eco- 

 nomic importance. With the 

 introduction of European 

 parasites of the moth during 

 and early 1930s, successful bio- 

 has generally been achieved. 



Satin modi larvae feed on aspen 

 leaves (above). Entire groves of aspen 

 can be defoliated by tlie satin mo^ 

 (right). Older, moisture-stressed trees 

 are the most vulnerable. 



'f 'o.r ^;J .fc 





Washington — 58 



