Sawfly Spells Trouble for Pine Trees in Northwest Alabama

Loblolly pine sawflies.  photo by Karl Byrd, AFC.

Alabama Forestry Commission News Release dated May 28, 2014:
During the last few weeks, there have been numerous reports from Northwest Alabama about dying pine trees.
Most of the visible damage is occurring on reasonably healthy, mature loblolly pines, growing in well-managed stands. According to officials with the Alabama Forestry Commission (AFC), the apparent culprits are larvae of the loblolly pine sawfly, feeding on and defoliating pine needles. With infestations reported in Colbert, Marion, Franklin, Lamar, and Fayette counties, the AFC is in the process of conducting aerial surveys of the affected counties. Infestation notices are being prepared for landowners where problems are detected, along with stand management recommendations. Although approximately 20 species of pine sawflies exist in the Southeast, the loblolly pine sawfly (Neodiprion taedae linearis) is the current aggressor. This particular species produces only one generation per year. Larvae attack in the spring, mainly from April to May, and host trees can be loblolly or shortleaf pines. A mature larva is approximately 1.25 inches long with a chocolate-brown colored head. The body is dull green with heavy black stripes along each side and lighter stripes below them. During an outbreak, most pines will not succumb to the infestation. The best recommendation is to wait and see if the infested pines rebound from the attack. Most will recover from this partial defoliation and start to grow lush green needles again by the summer. Because the loblolly pine sawfly is a native pest, population outbreaks are generally sporadic, localized, and widespread, significantly influenced by favorable climatic conditions and the presence of control biological agents. Natural predators such as birds, small mammals, and other parasitic organisms will prey on it, eventually reducing the population. Pathogens, viruses, and even starvation will also reduce the population. The use of insecticides is another option for controlling this defoliating pest, although cost prohibitive for large acreage. Insecticides are generally only used on infested pines in residential or commercial areas where aesthetics are an issue. If you suspect that your pine stand is under attack by the loblolly pine sawfly, please contact your local AFC office for further information or visit www.forestry.alabama.gov. The mission of the Alabama Forestry Commission is to protect and sustain Alabama’s forest resources using professionally applied stewardship principals and education, ensuring that the state’s forests contribute to abundant timber and wildlife, clean air and water, and a healthy economy.