Tree Species

- Aspen

- Balsam Fir


Pests and Diseases

Range of quaking aspenAspen is highly susceptible to fire damage. Major insect pests are forest tent caterpillar, large aspen tortrix, gypsy moth that feed on leaves, and various wood borers that weaken and degrade the stem. Several species of fungi cause stem cankers or white rot that reduce the volume of usable wood.

To reduce losses from these pests, do not grow aspen for timber where the site index is less than 60. Stands growing on poor sites are highly susceptible to pests. Try to regenerate 30,000 suckers an acre and maintain a high number of stems an acre to discourage poplar borer and hypoxylon canker. Do not thin aspen; wounds on residual trees will favor establishment of poplar borer and hypoxylon canker.

To minimize pest damage, harvest trees by age 40, unless the site index is at least 75 and veneer is the desired product. If fewer than 15 percent of the trees are infected with hypoxylon canker, stands may grow longer than 40 years. If 15 to 25 percent of the trees are infected with hypoxylon canker, harvest early and regenerate aspen. If more than 25 percent of the stand is infected, consider converting to an alternate forest type or species. Harvest early if white rot affects more than 30 percent of the basal area.

Repeated defoliation by forest tent caterpillar will weaken the trees, increasing their susceptibility to disease. Insecticides may be required to protect the stand during prolonged outbreaks.

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