The number of acres defoliated by western spruce budworm has declined sharply since 1992 (left) 

 compared to 1995 (right), especially in the Okanogan area (northeast corner of the state). Source. 



Cooperative Aerial Survey, Washingtor) Department of Natural Resources ar)d USDA Forest Service. 



Budworm populations have declined signifi- 

 cantly since 1992, when over 1.3 million acres 

 showed some defoliation in eastern Washing- 

 ton. The decline is attributed to a natural col- 

 lapse of the insect population and increased 

 precipitation. Areas of budworm defoliation 

 increased slightly in 1995 compared with 1994. 



Dwarf mistletoe abundance is tied to 

 host distribution, fire, and harvest — ^Dwarf 

 mistletoes are found on all of the conifers in 

 the mixed conifer forests of eastern Washing- 

 ton. The distribution and frequency of dwarf 

 mistletoe species closely follows the distribu- 

 tion and frequency of their hosts. Before 1900, 

 western larch dwarf mistletoe was the most 

 widespread mistletoe in late serai stands. 

 Western larch is less prevalent today but, be- 

 cause of selective harvest which creates con- 

 ditions favorable to spreading mistletoe, the 

 remaining larch have a high incidence of dwarf 

 mistletoe. 



In stands east of the Cascades, ponderosa 

 and lodgepole pine dwarf mistletoes were his- 

 torically more localized and less damaging than 

 now because of the frequency and sanitizing 

 effects of natural ground fires. Frequent 

 underburning minimized the accumulation of 

 fuels and the likelihood of stand-replacing fires. 

 Many stands had some dwarf mistletoe infec- 

 tion, but the severity was continually reduced 



by the frequent fires. In lodgepole pine, stand- 

 replacing fires at intervals of 90 to 200 years 

 eliminated mistletoe, along with the trees. In 

 ponderosa pine stands, fire suppression has 

 led to more widespread dwarf mistletoe. 



In ponderosa pine stands that have con- 

 verted to true fir and Douglas-fir because of 

 fire suppression, pine dwarf mistletoes have 

 decreased and fir mistletoes have increased. 



Western larch dwarf mistletoe can be extremely 

 damaging; mistletoe brooms on larch are brittle 

 and break off, leaving infected trees with few 

 branches. 



Washington — 55 



