Insect Infestation of Fire-Injured Trees in the Greater Yellowstone Area

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Permanent plots were established in the Greater Yellowstone Area (GYA) following the 1988 fires to determine response of bark beetles to fire-injured conifers. Within 2 years (1989 and 1990), 67 percent of the Douglas-fir had been infested by bark beetles (primarily the Douglas-fir beetle) and wood borers; 44 percent of the lodgepole pine were infested (primarily by the pine engraver)' 82 percent of the Engelmann spruce were infested (mostly by spruce beetle)' and 71 percent of the subalpine fir were infested (mostly by wood borers). Bark beetle infestation usually occurred in trees having 50 percent of more basal girdling by fire. However, uninjured Douglas-fir also had 46 percent of the trees infested in 1990. The large proportion of uninjured Douglas-fir that was infested by Douglas-fir beetle in 1990 suggests infestation will increase in unburned portions of the GYA. Of the trees that died, a fire-injury model correctly predicted death for one-half of the Douglas-fir and two-thirds of the lodgepole pine, but all of the Engelmann spruce and subalpine fir.


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