Southern Pine Beetle
Historically, southern pine beetles are the most destructive forest insects in South Carolina. They are indigenous, but populations are cyclic. The greatest recorded damage was in 1995-96 when $125 million worth of timber was lost to the beetle.
Adults are reddish-brown to black, one-eighth of an inch long, and stoutly cylindrical in shape.
Complete metamorphosis, consisting of egg, larva, pupa, and adult stages. The process from egg through adult takes about 28-54 days, depending on the season. Several generations may be produced each year in South Carolina.
- Adults emerge from brood tree, fly to another host tree.
- Adults bore into bark of new host and start constructing galleries in phloem/cambium. The initial attack frequently results in an extrusion of resin called a pitch tube. Adults usually live 6-14 days.
- Adults mate and lay eggs along the sides of the galleries.
- In 3-11 days, eggs hatch into tiny yellowish white larvae.
- The larvae feed for 15-40 days, constructing feeding tunnels in the phloem/cambium layer.
- The larvae bore into the outer bark where final development occurs. This is the pupae stage; it lasts 5-17 days.
- When the pupae have fully developed into adult form, they bore out of tree and fly to another host tree to begin a new cycle. The exit holes clean and free of resin.
Temperature extremes can disrupt the life cycle. Several consecutive days of 100-degree or 0-degree temperatures can disrupt the life cycle, leading to a collapse in population.
While there are always some southern pine beetles, beetle populations will occasionally increase dramatically to epidemic proportions. An epidemic cycle may last 3-4 years. Environmental factors and/or natural predators will eventually cause a population collapse, ending the epidemic.
Pine trees become especially susceptible to attack when under stress. Stress factors may include drought, flooding, fire, mechanical damage, poor nutrition, etc.
|Signs of Attack|
Commercial harvest or cut and leave. In either case, cut a buffer strip of green, uninfested trees at least equal to the height of the dominant trees in the stand. Fell trees toward the center of the spot. If using cut and leave, fell trees but do not cut them up into sections. Cut and leave is 80% effective in summer, but only about 60% effective in winter.