Stand conditions associated with roundheaded pine beetle (Coleoptera : Scolytidae) infestations in Arizona and Utah

Stand conditions associated with outbreak populations of the roundheaded Di ne beetle, Dendroctonus adjunctus Blandford, in ponderosa pine, Pinus ponde rosa Dougl, ex Laws., forests were studied in the Pinaleno Mountains, AZ, a nd the Pine Valley Mountains, UT. Classification tree models to estimate th e probability of infestation based on stand attributes were built for both study areas using growth rate and ponderosa pine basal area information. Cr oss-validation estimates of correct classification were 0.60 for the Pinale no Mountains and 0.58 and 0.78 for the Pine Valley Mountains. Regression tr ee and linear regression models to estimate amount of mortality caused by t he beetles were also built for both sites using growth I ate, ponderosa pin e basal area, and trees per hectare information. The occurrence and mortali ty levels caused by the roundheaded pine beetle are positively related at b oth the stand and tree scale with reduced growth rates caused by high stock ing densities.