Attacks of mountain pine beetle as related to tree vigor of ponderosa pine.
In central Oregon, Pinus ponderosa vigor (stem growth per unit of leaf area) decreased as both tree density (basal area) and leaf area index increased. Low vigor trees were more often attacked by Dendroctonus ponderosae than high vigor trees. Attacks increased below a vigor threshold of c.100 g of wood produced per square meter of leaf area per year, corresponding here to a basal area of 21 m2 ha-1 or a leaf area index of 2.9 m2 m- 2. Maintaining vigor through thinning will reduce the risk of mountain pine beetle attacks. -from Authors