Lumber Grade Yields from Spruce Budworm–Damaged Balsam Fir

In two grade yield studies conducted at a commercial sawmill in Northern Minnesota, 383 100-inch bolts, bucked from 149 balsam fir trees, were processed into lumber. Production of 2- by 4-inch and 2- by 6-inch dimension lumber was maximized. The sample of trees which were harvested included balsam fir which were healthy, stressed, or dying as a result of spruce budworm defoliation and dead standing trees which had been killed by the spruce budworm. Budworm-killed trees were harvested which had been standing dead approximately 6 months or less (including recently killed trees), 12 months, and 18 months. Results indicate that healthy balsam fir is capable of producing relatively high percentages of Standard or No. 2 and Better grades of dimension lumber. Over 56 percent of all dimension lumber sawn from bolts of healthy and budworm-stressed trees graded as Standard or No. 2 and Better. The rapid onset and advance of decay in the dead standing tree quickly erodes the potential for recovery of large percentages of dimension lumber in grades of No. 2 or Standard and Better from budworm killed balsam fir. Budworm-killed balsam fir continues to remain reasonably well suited to the production of dimension lumber grades of Stud or Utility or No. 3 and Better for up to 1 year after death. Over 63 percent of all dimension lumber produced from balsam fir standing dead 12 months was in grades of Stud or Utility or No. 3 and Better. Progression of decay with increasing time after death caused increasing downfall of lumber into the Economy grades.

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