Mountain Pine Beetle (Coleoptera: Scolytidae) Mortality in Three Types of Infestations

Publisher Website
Google Scholar
Abstract
Populations of mountain pine beetles, Dendroctonus ponderosae Hopkins (Coleoptera: Scolytidae), in lodgepole pine, Pinus contorta var. latifolia Engelmann, were sampled at three heights within trees in endemic, epidemic, and postepidemic infestations. Eight mortality factors were evaluated: competition within and between broods, parasites, predators, pathogens, winter temperature, drying of the phloem, pitch, and unexplained mortality. Beetle survival was significantly greater ( P < 0.01) in endemic (3.7%) than in epidemic (1.4%) and postepidemic (0.5%) infestations. Survival did not differ ( P > 0.05) by height in trees. Parasites and predators accounted for 8, 33, and 4% of total mountain pine beetle losses in endemic, epidemic, and postepidemic infestations, respectively. Medetera (13%) and woodpeckers (15%) accounted for the greatest amount of predation, and this occurred during epidemic infestations. Most parasites and predators showed the typical density-dependent response. Clerids were the single exception, taking a greater proportion of beetles in endemic infestations, thus suggesting a role by clerids in keeping mountain pine beetle populations at an endemic level. However, clerids accounted for only 0.9% of beetle losses.