Edward H. Holsten

Classification of spruce beetle hazard in Lutz and Sitka spruce stands on the Kanai Peninsula, Alaska

Abstract Stand data from Lutz and Sitka spruce forest types occurring on the Kenai Peninsula were analyzed by tree-based classification and abductive inference to develop decision models for classifying spruce beetle hazard. Model development and validation data sets contained 286 and 88 stand observations, respectively. The final decision-tree structure yielded 13 possible hazard outcomes based on total stand basal area, percentage of total basal area composed of spruce, percentage of spruce basal area composed of trees with diameter > 25 cm, stand elevation, and stand aspect. Four paths in the decision tree led to low-hazard outcomes (spruce basal area loss ≤ 10%); two paths each led to low-medium, medium, and medium-high hazard outcomes (spruce basal area loss of ≤ 40%, 11–40%, and > 10%, respectively); and three led to high-hazard outcomes (spruce basal area loss > 40%). Results of model verification were considered very acceptable; in the worst case, predictions of high hazard were correct for 67% of the observations. Model validation results also were considered acceptable, but predictions of medium and high hazard showed a marked drop from verification results. For comparison, the same analysis was performed using abductive inference to test a modeling method better suited to automatic processing of numerous stands for landscape-level analysis. There was a high degree of correspondence between predictions of the two analytical methods.

MCH Released in a Novel Pheromone Dispenser Prevents Spruce Beetle, Dendroctonus rufipennis (Coleoptera: Scolytidae), Attacks in South-central Alaska

Field tests of 3-methyl-2-cyclohexen-1-one (MCH), the antiaggregation pheromone of the spruce beetle, Dendroctonus rufipennis Kirby, were conducted in south-central Alaska in stands of Lutz spruce, Picea x lutzii Little, and Sitka spruce, P. sitchensis (Bong.) Carr. The deployment of MCH in a novel releaser significantly reduced trap catches and spruce beetle attacks on standing live spruce by 96 and 87%, respectively. The results of this study demonstrate the first successful field test of MCH in Alaska for the prevention of spruce beetle attacks on standing, live spruce.