. Insect and disease conditions in the United States, 1979-83 : what else is growing in our forests?. Forest insects United States; Trees Diseases and pests United States; Plants Disease and pest resistance. Douglas-fir Tussock Moth 5 Figure 6. Douglas-fir tussock moth outbreak Source: The Douglas-fir Tussock Moth: A Synthesis. Technical Bulletin 1585. Martha H Brookes, Stark, and Robert W. Campbell. U S Department of Agriculture, Forest Service. 1978. penses increase. As dead trees accumulate, the likelihood of catastrophic fires increases. Even- tually, fallen dead trees decay
. Insect and disease conditions in the United States, 1979-83 : what else is growing in our forests?. Forest insects United States; Trees Diseases and pests United States; Plants Disease and pest resistance. Douglas-fir Tussock Moth 5 Figure 6. Douglas-fir tussock moth outbreak Source: The Douglas-fir Tussock Moth: A Synthesis. Technical Bulletin 1585. Martha H Brookes, Stark, and Robert W. Campbell. U S Department of Agriculture, Forest Service. 1978. penses increase. As dead trees accumulate, the likelihood of catastrophic fires increases. Even- tually, fallen dead trees decay, and the fire hazard subsides. The larvae, pupal cases, and adults of the Douglas-fir tussock moth are covered with tiny, ir- ritating hairs. The hairs contain a chemical substance that causes an allergic reaction, known as tussockosis, in many people. Surveys have found 75 to 90 per- cent of the people coming in con- tact with these hairs will develop a temporary allergy. Pest Status From 1979 to 1983 Outbreaks of the Douglas-fir tussock moth during the 5 years from 1979 to 1983 were relatively small. Areas of visible defoliation are mapped in figure 8. Defolia- tion in urban areas is not includ- ed on the maps. The largest areas of defoliation occurred in Washington and Idaho (table 1). But surveys in the fall of 1983 indicate that popula- tions were declining in southwest Idaho and that populations in northeast Washington also were in various stages of collapse. Because populations did not build up enough to cause serious losses, no major control efforts were needed; however, 1,400 acres (567 ha) were treated in New Mexico during 1979. A nuclear polyhedrosis virus was used to treat areas where popula- tions were high enough to cause visible defoliation and where defoliation was likely to occur in the near future. Despite its relatively innocuous status in the early 1980's, the Douglas-fir tussock moth remains a threat. Within 1 or 2 years, populations can build to outbreak
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