Southern Pine Beetles Can Kill Your Ornamental Pine
Pine Bark Beetles - A Forest Menace
And They Can Be a Menace To You, Too
Appearance and Life Cycle
|Figure 3A. - Life stages of the
southern pine beetle - egg.
|Figure 3B. - Life stages of the
southern pine beetle - larval.
|Figure 3C. - Life stages of the
southern pine beetle - pupa.
|Figure 3D. - Life stages of the
southern pine beetle - adult.
Adult southern pine beetles are roughly 1/8 inch long, which is about the size of a grain of rice, and reddish brown to solid black. The insect goes through four life stages - egg, larva, pupa, and adult (Fig. 3) - in the inner bark of its host pine tree.
Eggs are mere pearly white dots. Larvae, or "grubs," are white, legless, and crescent shaped, with glossy reddish-brown heads. Pupae are also white but closely resemble the adult beetle shape.
Beetles mature in about a month and three to eight generations are born each year. Adults have wings; after killing the tree in which they were born, the beetles fly to another living pine to start the life cycle again.
How Beetles Kill Pines
The black turpentine beetle is the largest bark beetle in the South, about 1/4 inch long. Yet it is the least destructive because it attacks in smaller numbers, strikes fewer trees, and takes longer to kill them than the other species do. The black turpentine beetle likes the lower third of very weak or dying pines and will even make a home for itself in freshly cut stumps.
Southern pine beetles can kill a pine tree in a matter of days. Thousands of winged adults attack a single tree, bore through the bark, and hollow out egg "galleries." The females lay eggs in niches beside the galleries. In a week or so, larvae hatch and start chewing their way through the cambium - living conductive tissue - around the tree. This feeding "girdles" the pine and cuts off the normal flow of moisture and nutrients throughout the tree's system, quickly sapping its strength and contributing to its death. Adult feeding and a blue-stain fungus, which piggybacks its way inside pine bark on attacking adult beetles, help bring on tree death.
Symptoms of Beetle Attack
Successful attacks by southern pine beetles or by more than one species of Ips engravers always kill the tree. But if you act quickly enough, your pines can weather attacks by black turpentine beetles. Because control measures depend in part on whether or not the tree can be saved, you must first identify the species of beetle you are dealing with.
First signs of southern pine beetle attacks are popcorn-size lumps of pitch, called "pitch tubes," which occur at heights up to 60 feet (Fig. 5). The pitch tubes of black turpentine beetles are much larger - and appear at the foot of the tree (Fig. 6). Ips beetles rarely leave pitch tubes. During dry weather, pitch tubes do not appear; instead, red boring dust, which looks like fine red sawdust, will collect in bark crevices and at the base of the pine.
In later stages of southern pine beetle attack, you will be able to see small S-shaped feeding cuts on the inside of the bark (Fig. 7). Black turpentine beetles make vertical, wide etchings and Ips cut either Y- or H-shaped tunnels. The final sign of attack - and the sure mark of death for the tree - is a fade in needle color form green to yellow, red, and brown (Fig. 8).
Pines Likely to be Attacked
Some trees are apparently more appetizing to southern pine beetles than other trees. For instance, beetles seem to prefer loblolly, shortleaf, and Virginia pines to other kinds. During a beetle population explosion, however, the insects will take any species of pine available.
And old, unhealthy, or weakened pines of all species - whether diseased, damaged, or otherwise stressed - can be sitting ducks for southern pine beetles. Such trees have limited supplies of pitch, which is a tree's best natural defense against wood-boring insects.
What You Can Do to Prevent Beetle Attacks
Insecticides - an Ounce of Prevention?
What about insecticides? At present, two chemicals effective against all southern pine bark beetles are available, but this could change with new Environmental Protection Agency rulings. See your county agent about approved insecticides, amounts to use, and methods of application. Of course, be sure to read instructions carefully and to handle such compounds cautiously.
How to Control Beetle Spread
But what if it is already too late for an ounce of prevention? By the time you spot the telltale symptoms of beetle attack - pitch tubes, feeding cuts in the inner bark, and fading of tree foliage - it is too late to save the tree. You have only on move left. Stop beetle spread.
You can do this in two ways. First, if the beetles are still under the bark of the dead or dying pine, cut it down and haul it away or burn it. This should break up the center of beetle emergence and stop them from infesting other trees.
Second, spray the attacked pine with an approved insecticide, which will kill eggs, larvae, pupae, and adults still under the bark. Or, you can spray uninfested trees adjacent to the one under attack to protect them during the period of beetle emergence. Whichever method of control you choose, you must act quickly or the beetles will spread to other pines.
A Check List for Coping with Beetles
- Avoid damage to pines during yard work and construction.
- Keep pines healthy by watering and fertilizing them.
- Watch for pitch tubes and boring dust, especially in summer and spring.
- Quickly remove infested trees or spray with an approved insecticide.
The authors thank the Boyce Thompson Institute of Plant Research, Inc., for permission to use the chart on southern pine bark beetles, drawn by Richard Klieforth. For photographs, we thank the Georgia Forestry Commission in Macon, Forest Insect & Disease Management in Atlanta, Ga., and Asheville, N.C., and State & Private Forestry and the Bark Beetle Research Work Unit in Alexandria, La. We also appreciate the manuscript reviews and other assistance given by Extension-Forest Resources of North Carolina State University, the Texas Agriculture Extension Service of the Texas A&M University, the Texas Forest Service, and State & Private Forestry in Alexandria, La.