Identification and Biology of Southern Pine Bark Beetles

R.C. Thatcher – Program Manager, USDA Forest Service, Southern Forest Experiment Station, Integrated Pest Management Program, and
M.D. Connor – Entomologist, USDA Forest Service, Southern Region, Forest Pest Management.

Integrated Pest Management Handbook, USDA, Forest Service, Agriculture Handbook No. 634, March 1985.

In 1980, the Forest Service and the Cooperative State Research Service of the U.S. Department of Agriculture initiated the Integrated Pest Management Research, Development, and Applications Program for Bark Beetles of Southern Pines. This research/applications effort concentrates on pine bark beetles and associated tree disease in the South. This is one in a series of Integrated Pest Management handbooks.

Interrelationships Among Bark Beetles

A tree may be killed by the attacks of a single beetle species, but commonly others are present (see Fig. 7). Quite typically, the upper, central, and lower parts of larger trees are attacked by the small southern pine engraver, eastern five-spined, and six-spined Ips, respectively. The southern pine beetle may attack the central and lower parts of trees and be accompanied by two or more of the engravers in the central and upper parts, or the black turpentine beetle may be the first to attack the base of larger trees and subsequently be followed by one or several of the others. Zones of occupancy may overlap completely, making it difficult to determine which beetles attacked first, the role of the respective species in killing the tree, or the role of each species in predisposing the tree to attack by the others or in competing with one another for the same food supply.

The abundance of each bark beetle varies seasonally and during low vs. high activity periods. During peak activity periods (spring/early summer or late summer/early fall), the southern pine beetle is the primary attacker and survives well during outbreak years. During hot summers of outbreak years or low activity periods, one or more of the Ips engravers may be the principal tree killers, their survival is high, and the southern pine beetle is a secondary invader surviving in small sections of Ips infested or otherwise severely weakened or damaged trees (e.g., by lightning strikes).

Lightning plays an important role in the epidemiology of pine bark beetles (Fig. 10). Electrical storms occur frequently throughout the South providing an almost continuous source of lightning-struck trees during the growing season. These are colonized within a few hours or days by one or more species of bark beetles. It is not uncommon for more than 50 percent of the bark beetle infestations to be associated with lightning strikes during the summer months or periods of low southern pine beetle activity. Ips and black turpentine beetle populations often build up during the later stages of southern pine beetle outbreaks. These populations cause additional mortality in the surrounding residual forest. The small Ips may also attack nearby uninfested trees around southern pine beetle spots

Figure 10 – Lightning-struck pine is attractive to the bark beetle.

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