Southern 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
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.
50 Harry S. Truman Parkway, Annapolis, MD 21401