Southern Pine Beetle

Southern Pine Beetle DamageSouthern Pine Beetle (SPB), Dendroctonus frontalis, is one of the most destructive insect pests of pines. Maryland is in the northern range of this bark beetle. SPB is 2-4mm in length and is dark reddish brown to black in color. Loblolly is a preferred host of SPB, and tends to attack large mature stands of pine. SPB creates S-shaped galleries in the bark, and while feeding it inoculates the tree with a blue stain fungus. Following a mass emergence of SPB a shotgun pattern will appear from a tree. These outbreaks often occur after a mild winter or a hot, dry spring. 

A clerid beetle, Thanasimus dubius, is a predator of both adult and larval southern pine beetles. Additional natural enemies of SPB include other predators, woodpeckers, parasitoids, and diseases, which can reduce populations, but not stem an outbreak. One of the most effective SPB management tool is maintaining an appropriate stand density. Thinning a stand will change the microenvironment and help disrupt the beetle’s pheromone communication system. 

The southern Maryland counties and the southern Eastern Shore counties have been identified as at risk for SPB outbreaks by the US Forest Service. Those counties (Calvert, Charles, Prince Georges, Saint Mary’s. Talbot, Dorchester, Somerset and Worcester) are being surveyed during April and May for SPB. Lindgren funnel traps are set up in loblolly forests and checked weekly for six weeks. The number of SPB and the clerid predator are recorded. Using those numbers it is determined if the SPB population is declining, static, increasing, or at outbreak levels. In the past two years all populations of SPB in Maryland have been at low or declining levels with the exception of Dorchester County. The Andrews and Crapo areas of Dorchester County have seen 300 acres of pine mortality due to SPB. Some logging in these areas has occurred but populations are expected to spread as long as favorable conditions persist.