The Southern Pine Beetle, Dendroctonus frontalis Zimmermann

The southern pine beetle (SPB), Dendroctonus frontalis Zimmermann, is the most destructive insect pest of pine in the southern United States. A recent historical review estimated that SPB caused $900 million of damage to pine forests from 1960 through 1990 (Price et al. 1992). This aggressive tree killer is a native insect that lives predominantly in the inner bade of pine trees. Trees attacked by SPB often exhibit hundreds of resin masses (i.e., pitch tubes) on the outer tree bark (Fig. 1). SPB feed on phloem tissue where they construct winding S-shaped or serpentine galleries (Fig. 2). The galleries created by both the adult beetles and their offspring can effectively girdle a tree, causing its death. SPB also carry, and introduce into trees, blue-stain fungi. These fungi colonize xylem tissue and block water flow within the tree, also causing tree mortality (Thatcher and Conner 1985). Consequently, once SPB have successfully colonized a tree, the tree cannot survive, regardless of control measures. When beetle populations are low (endemic), attacks are generally restricted to senescent, stressed or damaged pines; however, epidemics periodically occur (Thatcher et al. 1980). During epidemics, SPB infestations often begin in weakened or injured trees, but the high beetle populations can invade and overcome healthy vigorous trees by attacking in large numbers over a short period of time (Thatcher et al. 1980). Widespread and severe tree mortality can occur during epidemics. SPB spots (groups of infested trees) may expand at rates up to 50 ft. (15 m)/day, and uncontrolled infestations may grow to thousands of acres in size (Ron Billings, Texas Forest Service, personal communication). SPB attacks are not limited to conventional forest sites; they also may kill high-value trees in yards, parks, and other ornamental settings (Thatcher et al. 1978). Because of the seriousness of SPB infestations, care should be taken not to confuse· SPB with the less aggressive but more common pine bade beetles of Florida, the pine engravers (lps spp.) and the black turpentine beetle (D. terebrans (Olivier)) (Dixon 1984, 1986).