Southern Pine Beetle

Dendroctonus frontalis Zimmermann

Order Coleoptera: Family Scolytidae

Description: Adults are cylindrical, somewhat stout, 2 to 4 mm long, and brownish to black in color.  The head broad and prominent with median elevations forming a distinct frontal groove.  Females are distinguished from males by the presence of a broad, elevated ridge on the pronotum.  Larvae are wrinkled, yellowish-white, legless grubs with prominent heads and stout, dark mandibles.  Mature larvae are about 7 mm long. 

Hosts: Various species of pines

Damage: The insects damage the inner bark and  cambium layer of trees, causing tree death.  Harvested volume is sharply reduced due to unsalvaged merchantable trees, harvesting trees ahead of schedule, or both.  The value of salvaged timber may also be reduced by decay, stain or insect holes.  Galleries excavated under the bark by southern pine beetles are commonly curved or S-shaped.  This can distinguish their damage.

Life Cycle: Southern pine beetles overwinter in all life stages in the bark of trees.  Development of all stages continues throughout the year, although it is much slower in winter.  Adults lay eggs in their excavated galleries.  Eggs hatch in two to nine days and the larvae enter the cambium layer, then the inner bark, enlarging their galleries as they grow.  When mature, larvae bore to the outer dead bark, create a cell and pupate.  Emerging adults bore out of the pupal cell directly through the outer bark, leaving a clear-cut,  open hole.  Adult emergence may continue for an extended period of time.  Generally, emerging adults leave the host tree and aggregate on an adjacent tree or leave the area to find a suitable new host tree.

Control: At present, four direct control options are available:  (1.) removal and utilization or sale of infested trees (rapid salvage); (2.)  cut-and-leave or cut-and-top; (3.) fell and spray with insecticides, and; (4.) fell, pile and burn infested trees.  In high value situations, residual insecticides can be sprayed for remedial control or prevention.

Updated from: Horton, D. L. and H C Ellis, 1997.  Weevils and Borers.   In:  Hudson, R. D. and D. B. Adams.  1997.  A County Agent's Guide to Insects Important to Agriculture in Georgia. Entomology 97, RDH (1).  Univ. of GA, Col. Ag. Env. Sci, Coop. Ext. Serv., Tifton, GA 31793.

Photo by Forest Insects and Their Damage Photo CD vol. 1 no. 88. Gerald Lenhard, Louisiana State University.

SPB Galleries.
Note Frass in Galleries.
Photo from Southern Forest Insect Work Conference set

SPB Pitch Tubes
on Tree Trunk
Photo from Southern Forest Insect Work Conference set