. Forest insect and disease conditions in the United States 1979. Insect pests United States. in Oregon. Losses in the Intermoun- tain Region were minimal. Douglas-fir tussock moth defolia- tion dropped off sharply in the South- west and also declined in California. In the Rocky Mountains, damage was confined to urban areas of the Front Range. Poplulations were low in Montana and the Pacific North- west. In Alaska, the spruce beetle dra- matically increased in 1979 to cover about acres(an increase of acres over 1978). Large aspen tortrix populations remained high for a second c
. Forest insect and disease conditions in the United States 1979. Insect pests United States. in Oregon. Losses in the Intermoun- tain Region were minimal. Douglas-fir tussock moth defolia- tion dropped off sharply in the South- west and also declined in California. In the Rocky Mountains, damage was confined to urban areas of the Front Range. Poplulations were low in Montana and the Pacific North- west. In Alaska, the spruce beetle dra- matically increased in 1979 to cover about acres(an increase of acres over 1978). Large aspen tortrix populations remained high for a second consecutive year. The dwarf mistletoes, as in pre- vious years, caused serious losses to commercial conifers in the West and Alaska. The major impact of this group of diseases is growth reduc- tion. Estimates indicate that over 18 million cubic feet of wood are lost to dwarf mistletoes each year in the Southwest. Forty-two percent of the host t\pe in Oregon and Washington is infected. Field surveys and com- puter yield programs were used to determine economically feasible management strategies for dwarf mistletoe infected stands. The incor- poration of mistletoe control pro- cedures into silvicultural prescrip- tions is becoming more common. Root diseases accounted for major tree losses in most Western areas. The majority of damage was at- tributed to laminated root rot. an- nosus root rot. armillaria root rot. and black stain root disease. On certain sites more than 25 percent of the trees are infected with annosus root rot. Root disease was often associated with pest management activities and tree wound- ing, and. in general. obser\'ations sug- gest that these problems are becoming more serious. Needle diseases were more visible in many locations, but in the Pacific Northwest incidence declined. There may be growth losses in situations of extreme or repeated defoliation. Winter injuty was very common throughout the West and was the most spectacular tree damaging agent in the N
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