File:Protecting and enhancing America's forests and rangelands - 1986 research accomplishments (1987) (20573283465).jpg

Title: Protecting and enhancing America's forests and rangelands : 1986 research accomplishments
Identifier: CAT88893232 (find matches)
Year: 1987 (1980s)
Authors: United States. Forest Service
Subjects: Forests and forestry United States; Rangelands United States
Publisher: (Washington, D. C. ) : U. S. Dept. of Agriculture, Forest Service
Contributing Library: U.S. Department of Agriculture, National Agricultural Library
Digitizing Sponsor: U.S. Department of Agriculture, National Agricultural Library

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Silvicultural Options for Reducing Forest and Stand Susceptibility to Western Spruce Budworm The western spruce budworm, a serious insect defoliator of western conifer forests, can cause extensive damage under certain forest and stand conditions. Outbreaks of the budworm occur in dense, multistoried stands composed mostly of host trees that are shade tolerant, such as grand and white firs and Douglas- fir. These stand conditions occur over much of the range of budworm, primarily because (1) the frequency of forest fires has been very low compared to pre-1910 periods, allowing the shade-tolerant species to proliferate; and (2) selective harvesting practices have removed much of the shade-intolerant or "serai" conifer species, such as ponderosa pine and western larch, which are not primary hosts for the insect. Reducing the habitat that favors budworm epidemics by using silvicultural methods is an effective long-term approach for dealing with this pest in the northern U.S. Rocky Mountains and perhaps elsewhere. Even-aged silvicultural practices, such as clearcutting and seed-tree and shelterwood cutting, can be used to create conditions unfavorable to budworm. Shade-tolerant hosts are removed and replaced with the fast-growing and productive serai pines and larch. Stands like this are poor for budworm but excellent for timber, wildlife, and recreation. These stands usually are not multistoried, and stand density is easily controlled to optimal levels. In prime budworm habitat, conversion of uneven-aged host stands to mosaics of even-aged stands will dramatically reduce the budworm problem over the length of a single rotation. Whether or not susceptibility to and damage by the budworm can be reduced forestwide will depend on forest economics, the political climate, and the willingness of forest managers to make provisions for budworm control in their forest- management planning.
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Douglas-fir is extremely susceptible to western spruce budworm attack. Therefore, in areas where it is the climax species, Douglas-fir should be harvested and a few seed trees of less susceptible species, such as pine and larch, should be left behind, to provide a next generation of trees that will be less likely to appeal to the budworm. Since this photo was taken, the overstory of seed trees has been removed. What remains is a thrifty young stand with very low susceptibility to western spruce budworm. Even-aged silviculture like this--not extensive spraying--is the key to effective budworm management in the West. 40

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