The Spruce Budworm in Maine: 1976
- Trial, Jr., Henry
Maine Forest Service
- Struble, David
Maine Forest Service
In 1976 the Maine Forest Service conducted a 3.5 million acre aerial spray project against the spruce budworm in northern and central Maine. The goal of the operation was to reduce budworm populations and associated defoliation to prevent substantial tree mortality in high hazard areas. The chemicals used were carbaryl (Sevin-4-oil) applied at the rates of 3/4 lb. and 1 lb. A.I. per acre, and trichlorfon (Dylox-4) applied at the rate of 1 lb. A.I. per acre. Total cost of the project was $8,526,580.
Larval development was erratic due to early unseasonably warm weather followed by very cold, wet weather and finally by very warm conditions again. Some larval mortality was noted following the extreme cold, wet weather.
Prespray larval populations were generally far below the unprecedented high levels of 1975, but were nevertheless high enough to cause complete defoliation in most areas scheduled for spraying in 1976. The immediate mean population reduction in the sprayed area, adjusted for natural mortality was 86.2%. Mean defoliation in the treated area was 29.16% compared to 86.82% in the adjacent unsprayed areas. Mean survival numbers in the treated area were less than 1 budworm per 18' tip and several portions of the treated area had less than 0.5 survivors per 18' tip. The aggregate budworm parasitism over the entire budworm area was approximately 38%. Light trap survey data did not indicate any widespread moth flights. The average density of egg masses for all areas, in and adjacent to the 1976 spray area, was 192 compared to 545 in 1975.
Cooperative and research and monitoring projects conducted by the U.S. Forest Service, Maine Fish and Wildlife, U.S. Fish and Wildlife and the University of Maine are listed.
Hazard ratings based on ground surveys for egg masses and tree condition, supplemented with an aerial damage survey indicated that approximately 930,000 acres of spruce and fir would be in critical condition in 1977. Lacking reductions in projected budworm larval populations, substantial tree mortality is expected in these critical areas.
Efforts in 1976 and forecasts for 1977 in adjacent Canadian provinces and the State of New Hampshire are discussed.
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