Attacks of Mountain Pine Beetle as Related to Tree Vigor of Ponderosa Pine

Abstract

Abstract The relationship between tree vigor, measured as stem growth per unit of leaf area, and susceptibility to mountain pine beetle attacks was examined in a stocking-level experiment of ponderosa pine ( Pinus ponderosa Laws.) in central Oregon. Vigor decreased as both tree density (basal area) and leaf area index increased. Low vigor trees were more often attacked by beetles than high vigor trees. Attacks increased below a vigor threshold of about 100 g of wood produced per square meter of leaf area per year, corresponding in this study to a basal area of 21 m² ha -1 or a leaf area index of 2.9 m² m -2 . For management of ponderosa pine, maintaining vigor through thinning will reduce the risk of mountain pine beetle attacks. Forest Sci. 29:395-402.