Mortality Associated with a Bark Beetle Outbreak in Dwarf Mistletoe-Infested Ponderosa Pine Stands in Arizona

Abstract

Abstract Ponderosa pine (Pinus ponderosa Douglas ex C. Lawson var. scopulorum Engelm.) mortality was evaluated from a 2002 bark beetle outbreak in areas infested with southwestern dwarf mistletoe (Arceuthobium vaginatum [Willd.] Presl subsp. cryptopodum [Engelm.] Hawksw. & Wiens) in a total of nine study sites in northern Arizona. Ponderosa pine mortality attributable to bark beetles (Ips and Dendroctonus spp., Scolytidae) was systematically sampled, and stand attributes, such as basal area, tree density, dwarf mistletoe severity, and site indices were recorded. Ponderosa pine mortality was predominately attributed to Ips spp. Although the prolonged drought likely was the inciting factor responsible for the Ips spp. outbreak, results suggested a strong relationship between ponderosa pine mortality and the interaction between crown class and dwarf mistletoe rating class. Ponderosa pines severely infected with dwarf mistletoe and in the intermediate crown class are at the greatest risk of Ips spp. attack during outbreak years in northern Arizona.