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.

General Characteristics

Symptoms of Attack

Discolored foliage – The most noticeable indication of beetle attack is discolored foliage. Needles first fade to a yellowish color, then change to red, and become brown within 1 to 4 months after initial attack. Discoloration of the whole crown is typical of trees killed by the six-spined and eastern five-spined Ips, the black turpentine beetle, and the southern pine beetle. The small southern pine engraver, on the other hand, often kills only the top of the crown or individual branches (Fig. 1). The southern pine beetle kills groups of trees (commonly referred to as spots) ranging from a few trees to stands covering hundreds of acres (Fig. 2). Trees crowns usually are green or yellowish along the edges of the spot where the beetles are still active, and red, brown, or completely bare in the older portions of the spot. Ips and black turpentine beetle infestations usually involve scattered singletrees or very small groups, and most trees in a group have the same foliage color.

Figure 1 – Crown or top kill by Ips avulsus.

Figure 2 – Aerial view of expanding southern pine beetle infestation.

Southern pines may also be killed by fire, herbicides, diseases, and defoliators. Close examination may be necessary to determine whether bark beetles are involved. Other symptoms of bark beetle attack are:

Pitch tubes – Pitch tubes mark the points of beetle entry through the bark. Those resulting from Ips engraver and southern pine beetle attacks, mostly located in bark crevices on the main trunk and larger limbs, are usually dime-size or smaller (Fig. 3). Ips pitch tubes are reddish, while those caused by the southern pine beetle are whiter. Black turpentine beetle pitch tubes, usually quarter-size or larger (Fig. 4), are confined to the basal 12 feet of the trunk and to the base of larger roots. Unlike the other bark beetles, turpentine beetles sometimes continue to attack a given tree over a period of several months. If tree mortality does occur, it may be delayed.

Figure 3 – Pitch tubes, the first sign of southern pine beetle or Ips attack.

Figure 4 – Black turpentine beetle pitch tubes at the base of the trunk.

Boring material – In unusually dry weather, trees under stress may fail to produce pitch tubes following southern pine beetle or Ips attack. Reddish boring dust in bark crevices or on spiderwebs and leaves of understory vegetation may be the only visible sign of bark beetle attack (Fig. 5).

Figure 5 – Southern pine beetle and Ips boring dust in spider webs at the base of the tree.

Figure 6 – Ambrosia beetle boring dust at the base of a bark beetle-killed tree.

Yellowish-white resin pellets usually occur in bark crevices and at the base of the tree beneath turpentine beetle attacks. Later on, fine white boring material from ambrosia beetles may also be seen around the bases of beetle-attacked trees (Fig. 6). Although the foliage of these trees may still be green, such symptoms indicate that the trees have been overcome by beetles and are dead or dying.

Insect galleries (refer to Fig. 7) – Removal of bark from infested pines that have been under attack for one to several weeks will generally reveal egg gallery patterns characteristic of each bark beetle species. Southern pine beetle galleries are curving or S-shaped. The galleries are plugged with boring material and crisscross in the inner bark and on the wood surface. Ips galleries have a central chamber from which two to four egg galleries radiate. Together they form I-, Y-, or H-shaped patterns in the inner bark. Black turpentine beetle galleries are large (up to 1 inch wide and 12 or more inches long), run with the wood grain, and are often filled with resin.

Figure 7 – Areas of the trunk usually infested by the major pine bark beetles in the South. From top to bottom: small southern pine engraver, eastern five-spined Ips, six-spined Ips, southern pine beetle, and black turpentine beetle. Note the area of the trunk and the gallery patterns associated with each species, the life stages of Ips vs. Dendroctonus spp., and the rounded vs. concave rear ends of the Dendroctonus vs. Ips spp. (Courtesy of Texas Forest Service).

Figure 8 – Southern pine beetle pitch tubes and exit holes through the bark.

Adult exit holes – Adult bark beetles exit by tunneling through the bark. Exit holes are made by parent adults that reemerge after mating and laying eggs and by brood adults that emerge following development in or beneath the bark. Ips and southern pine beetle exit holes resemble small shotgun pellet holes (Fig. 8). Exit holes made by turpentine beetles are considerably larger (about 1/8-inch in diameter).

Description of Life Stages²
Bark beetle eggs are pearly white, very small, and difficult to see with the unaided eye. They are laid within individual niches (southern pine beetle and Ips spp.) or in one or more clusters along the gallery walls (black turpentine beetle). The larvae are whitish, legless, and c-shaped with glossy, reddish-brown heads. Their size varies according to species and stage of development. The resting stage (pupa) is white, very soft, and similar to the adult beetle in size. New adults are a light tan or amber color, but darken to reddish-brown or black as they mature. They are short-legged and stout, and vary in size by species. The hind end of the body of southern pine beetles and black turpentine beetle is rounded. The rear end of Ips engraver beetle is concave (scooped out) and has four to six spines on each side (four spines for Ips avulsus; five for Ips granicollis; six for Ips calligraphus).

²Also refer to Figure 7.

Seasonal Infestation Patterns
Overwintering broods of the southern pine beetle emerge and begin to attack uninfested trees in early spring--about the time that dogwood trees flower. In the Gulf States, emergence and attacks may occur during warm, mild winters. Outbreaks usually peak in late spring or early summer in those States and in late summer or early fall farther north. All life stages may be observed in the same infestation throughout the season.

The black turpentine beetle is sometimes active throughout most of the year in the deep South. In the cooler months, development and new attacks slow down.

Ips and black turpentine beetles are usually most active during the warmer, drier portion of the year. Pine stands weakened or damged by extended drought, storm damage, fire, or logging may, however, be attacked by one or more species throughout the growing season.

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