Pine Bark Beetles
Cooperative Extension Service, College of Agricultural and Environmental Sciences, The University of Georgia Bulletin 1097, October 1993, 8 pp.
Southern Pine Beetles
SPB are about 3 mm (1/8 inch) long, have rounded abdomens and are brownish to black in color (Figure 6). SPBs are the most important bark beetle pests in the southern United States and occur from Delaware south to Florida and west to Texas. They infest all species of pine indigenous to the South. Shortleaf and loblolly are most susceptible, while slash and longleaf pines are generally considered to be more resistant to SPB attack. SPBs have broad and prominent heads, with median elevations that form distinct frontal grooves. Egg galleries produced by females are serpentine or s shaped (Figures 5 and 10) and are normally packed with a brown frass (feces) and boring dust produced by the beetles. Pitch tubes are fairly small, usually less than ½ inch in diameter and are generally in bark crevices (Figure 11). On severely weakened trees, brown boring dust accumulated in bark crevices or on spider webs is often the only visible sign of early attack.
|Figure 10. SPB Galleries.
Note Frass in Galleries.
|Figure 11. SPB Pitch
Tubes on Tree Trunk.
SPBs normally infest open trunks of trees from the base to the crown, usually attacking first at mid-trunk or in the lower crown (Figure 4). After the first beetles arrive, mass attack occurs as large numbers of beetles respond to pheromones and host attractants. SPB galleries normally contain one pair of adults. The female begins constructing a gallery and is joined by a male. After mating, the female continues to excavate the gallery and lays eggs along both lateral walls of the gallery. Eggs are deposited singly, in discrete cavities (egg niches). Both males and females "reemerge" or leave the host to infest another tree.
The life cycle takes 35 to 60 days, and there may be as many as six generations each year in Georgia. When brood development is complete, the new beetles bore their own exit holes. Trees from which the brood has emerged are covered with large numbers of small ( 1/16 inch in diameter) emergence holes.
SPBs carry blue stain fungi on their bodies and introduce it into the tree during their attack. Con sequently, trees that have been successfully colonized by SPBs cannot be saved, even if larvae are killed by an insecticide treatment.