Southern pine beetle infestations in relation to forest stand conditions, previous thinning, and prescribed burning: evaluation of the Southern Pine Beetle Prevention Program
Since 2003, the Southern Pine Beetle Prevention Program (SPBPP) (a joint effort of the USDA Forest Service and Southern Group of State Foresters) has encouraged and provided cost-share assistance for silvicultural treatments to reduce stand/forest susceptibility to the southern pine beetle (SPB)(Dendroctonus frontalis Zimmermann) in the southeastern United States. Until now, stand- and landscape-level tests of this program’s efficacy were nonexistent. In 2012, SPB outbreaks occurred in the Homochitto and Bienville National Forests (NFs) in Mississippi. Parts of each NF were treated (thinned) using SPBPP management recommendations, whereas other areas were untreated (unthinned). In the Homochitto NF, 99.7% of SPB spots occurred in unthinned stands, whereas all SPB spots occurred in unthinned stands in the Bienville NF. Unthinned stands in both NFs had higher basal area, higher stocking, and lower growth rates over the last decade. Burning also resulted in a lower incidence of SPB infestation. Our retrospective study results validate the effectiveness of SPBPP treatments for reducing stand- and landscape-level susceptibility to SPB, which encourages proper silvicultural methods that increase tree spacing, growth, and vitality, while effectively altering the in-stand atmosphere enough to interfere with SPB pheromone communication, thus reducing susceptibility to SPB spot initiation and spread.