Insect and Disease
 Current Problems

Current problems being closely monitored by the Insect and Disease Section include southern pine beetle, annosus root rot, pales and pachylobius weevil, and a myriad of other pests.

Bug Spot

Southern Pine Beetle

The southern pine beetle is the most destructive insect enemy of pines in the southern United States. Each year it kills millions of dollars of valuable timber resources and has earned the reputation of being the most feared insect by southern forest managers and timber landowners.

Periodically this beetle develops epidemic populations which kill large stands of timber, sometimes exceeding several hundred acres in size. What triggers the explosive outbreaks is not completely understood. Most entomologists believe these epidemics to be the result of complex and interacting factors favoring beetle development. However, through the years, poor tree vigor appears a main factor associated with southern pine beetle outbreaks. This can be caused by many weakening factors leading to stand stress, leaving the trees easy prey for attacking beetles. The key to minimizing losses to the southern pine beetle is reducing stand stress through good forest management practices.

IDENTIFICATION: The southern pine beetle is a small reddish-brown to black beetle about one-eighth to three-sixteenths of an inch long.

Pitch Tubes

TREES THEY ATTACK: All species of southern yellow pines, but prefer shortleaf, virginia, loblolly, pitch, and pond pines.

HOW THEY ATTACK: SPB attack living pines by boring through the bark and constructing galleries in the cambium layer where they lay their eggs. The mining in the cambium layer girdles the tree and introduces blue stain fungi which reduces or blocks conduction of water in the tree's trunk, killing the tree.

RECOGNIZING DAMAGE: The beetles kill pines in patches ranging from one tree to thousands of trees. Usually the first sign of an infestation is discolorization of tree crowns. trees fade to a dull green, turn yellow, become straw colored and finally turn reddish-brown within one to two months. Small, light yellow or white pitch tubes formed at the beetle's entrance holes may be seen along the entire length of the tree's trunk. These masses of pitch often resemble popcorn in size, shape , and color but are not always present. Close examination of the tree will show reddish boring dust lodged in crevaces or at the base of the tree.

Contact the Insect and Disease staff if you believe you have southern pine beetles.

Southern Pine Beetle Facts

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Annosus Root Rot

Annosus root rot is a major disease problem of pines and other conifers. Affected trees grow at a slower rate and are more susceptible to attack by bark beetles. Annosus is caused by a fungus. Spores from this white rot fungus are produced in structures called conks. These develop at the base of infected trees and stumps. Conks are usually small and difficult to locate unless the duff layer is removed from around the tree. Most infected trees , however, do not produce conks.

IDENTIFICATION: Severely affected trees may have thin, light green to yellow crowns, with tufted branches and short needles. Infected roots are initially resin-soaked and brownish-red, but become a white, stringy mass of decayed tissue.

WHERE DOES IT OCCUR: The disease is more common and sever on sites with low water tables and 12 inches or more of soils containing at least 65 percent sand.

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Pales and Pachylobius Weevil

The pales and pachylobius weevil cause losses in new pine plantations by feeding on the bark of seedlings. Enough of this feeding girdles the seedling and kills it.

Adult pales weevils are attracted to the scent of fresh pine stumps. They lay eggs in the stumps from which larvae hatch. The larvae feed on the inner bark of the stump and mature into more adult weevils.

Weevils colonize stumps regardless of when the tree was cut. However, if the trees are not cut before July, the weevil larvae will mature and emerge before tree planting season. Problems for forest managers occur when pine stands are harvested after the first of July. In these areas the weevils will be active at the time seedlings are planted. This can result in a partial or complete loss of seedlings.

Seedling damage by weevils can be prevented by delaying planting of the site for one year if it was harvested after the first of July. If this is not practical, seedlings can also be chemically treated in the nursery with Pounce insecticide. This is done just prior to lifting seedlings and will protect them for about 2 months after they are planted. Most forest nurseries now do this treatment for a minimal fee on a request basis.

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Insect and Disease