- Wickman, B.E.
U.S. Department of Agriculture, Forest Service
The spruce budworms are the most widely distributed and destructive forest defoliators in North America. In the caterpillar stage they consume foliage and attack new buds, cones, and terminals of spruces, true firs, Douglas-fir, and associated conifers including western larch. They are native insects of spruce-fir forests in the Northeast, Lake States, Western United States, and Canada. Widespread and destructive outbreaks have resulted in serious growth loss, top-killing, and tree mortality in all age classes. During the last 4 years, infestations have fluctuated from 1.5 million to 7.9 million acres in the Northeast and Lake States and from 4 to 6 million acres in the West. Since 1949, 2.5 million acres have been aerially sprayed in the Northeastern States and Lake States to reduce tree damage and mortality. In the West, 12.3 million acres were similarly treated during the same period.
The ecological and economic impacts of the spruce budworms may be slight and transitory or severe and long lasting depending on the intensity and duration of infestation and the resource values affected. Tree mortality does not always follow outbreaks; thus the damage, which often occurs over vast areas, has been inadequately assessed. The less striking effects of defoliation on growth loss and form of trees, forest stands, and loss of seed through cone destruction can be significant.
Single-thrust approaches to suppression of spruce budworms with chemicals have not always succeeded. More accurate and reliable means of assessing and predicting population trends and the consequent impacts must be developed to better judge when and where to take remedial action. Moreover, the diversity of ecological conditions over the eastern and western coniferous forests of the United States, the values involved, and other considerations require a variety of pest management strategies.
A Program of research and development activities is proposed to make new and improved budworm control and population assessment methods available to land managers within 5 years. Emphasis will be on development of selective chemical, biological, and silvicultural methods of control with minimal adverse effects on nontarget organisms and the forest environment.
Total funds required for the proposed Program during the 5-year period are $52,905,000. Forest Service funds available in FY 1975 for research on the budworms total $185,000.
The Program approach would greatly increase cooperation and effectiveness of the research, survey, and development work presently carried on by the various States, universities, and Forest Service, USDA. A significant amount of research would be carried out through contracts and cooperative agreements with States, universities, and research organizations.
The ongoing USDA Douglas-fir Tussock Moth Program in the West has important relationships to the proposed Spruce Budworms Program. The tussock moth and the western spruce budworm are pests of the same forest ecosystems. Much technology from the DFTM Program will be applicable to management of western spruce budworm populations.