Southern pine beetle (SPB),
Southern pine beetle (SPB), is one of the most destructive pests of pines in the southern United States, Mexico, and Central America. It occurs in the southern and southeastern United States, extending as far west as Arizona and as far south as Central America. The northern range extends from southern New Jersey and Pennsylvania, west to southern Missouri, south to east Texas, and east into Florida. Generally, this insect occurs wherever Shortleaf and Loblolly Pines are grown. This insect killed approximately 4.5 million board feet of pine timber from 1973 through 1977 in the southeastern United States.
In the southeastern states, Loblolly and Shortleaf Pines are preferred, though Virginia, Pitch, Table-mountain, Longleaf, and Slash Pines are often also successfully attacked.
Description of Damage
Southern pine beetles are mass-attack the trunks of mature or over mature pine trees. The beetles bore directly through the outer bark into the living bark and develop "s-shaped" galleries in the phloem tissue which cut across one another and girdle the tree. This is also where the eggs are laid and broods develop. They also introduce a blue-stain fungus into the sapwood that eventually inhibits water flow in the tree. The colonization by the beetles and the fungus combined results in tree death only days after mass-attack. The first indication of tree mortality is discoloration of the foliage. Needles become yellowish, change to a red color, and-finally turn brown. It may take weeks or even months (if attacks are in late fall) for the foliage to fade from green to red. Pitch tubes are often present at the entrance holes made by the beetles which are about the size of a small piece of popped popcorn. In addition, reddish-yellowish boring dust may also be present in bark crevices or around the base of the tree. The tree attempts to pitch out the beetles and is sometimes successful.
Beetle populations will remain at endemic levels for years, causing damage to single trees or small groups. Often, these spring infestations do not continue and will die out. However, when populations are high, infestations can expand almost like wildfire within pure pine stands, killing thousands of trees and covering hundreds of hectares. Epidemic levels generally last for a two or three year period. These cycles between endemic and epidemic populations occur about every 10 years.
For trees that are killed, loggers try to salvage the wood as quickly as possible to minimize the amount of degrade. The blue-stain fungus is apparent in the sapwood, reducing the price at which sawtimber is sold.