Phenotypic variation within southern pine beetle, and effects of prescribed fire on tree mortality during an ips bark beetle outbreak

The southern pine beetle (Dendroctonus frontalis) (SPB) and the southern pine engravers, Ips avulsus, I. calligraphus, and I. grandicollis, colonize southern pines and can cause mortality and economic losses at high population levels. We examined SPB phenotype variation (body size, hindwings, and sex ratios) between outbreak and non-outbreak population phases, and found traps in non-outbreak areas caught ~2 times higher proportions of females. We monitored southern Ips infestations between burned versus unburned sites, and observed 3.6 times higher pine mortality on unburned sites and a higher probability of tree survival on burned sites. Models including treatment and month best predicted site-level mortality, and a model including treatment, crown mortality level, Ips activity level, and DBH best predicted tree-level mortality. Including the captured proportion of females in SPB outbreak prediction models may improve forecasting, and using prescribed fire during Ips infestations may increase resilience of pine forests in the southeastern U.S.