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Redheaded pine sawflies being reported

The Texas Forest Service Office in Gilmer has received several phone calls the past few days about young pine trees being attacked by caterpillar-like worms. Based on descriptions of the “worms” they have been identified as redheaded pine sawfly larvae, which is one of several specie of sawflies native to Texas. Sawflies are not true flies, but are actually wasps and get their name from the saw-like structure on the end of the female’s abdomen. The female sawfly uses this structure, or ovipositor, to cut small slits in the pine needles in which to lay eggs.

The adult or wasp stage of the sawfly is seldom seen and only causes minimal damage to plants when the female deposits her eggs. It is the larval stage that consumes the needles and causes damage. Sawfly larvae superficially resemble a moth or butterfly (Lepidoptera) caterpillar.

The redheaded pine sawfly is particularly damaging to young pine plantations and is an occasional problem in Christmas tree farms and ornamental trees. Sawfly outbreaks in young plantations sometimes spread over large areas and may persist for several years.

Redheaded pine sawflies over-winter in a dormant larval stage changing to pupae in early spring with adults emerging a few weeks later. Females deposit 100 or more eggs in rows of slits they saw in the edges of needles with usually one egg laid in each slit. The female produces living eggs even though she may not have mated with a male sawfly. Fertilized eggs produce both male and female offspring, but the unfertilized eggs produce only females. When weather conditions are favorable, as many as five generations may be produced in one year.

The larvae emerge from the eggs in 15-30 days and begin to feed in groups on the pine needles, usually feeding on a tree from top to bottom, completely defoliating one branch before moving to another. They may even feed on the tender bark of young twigs and small trees that are completely defoliated often die.

Full-grown larvae are about an inch long (22-25mm), have a rust-red head and a hairless, yellowish-white body with six rows of black dots. When the larvae are mature, they drop to the ground and spin a tough, egg-shaped tan to reddish-brown cocoon in the soil or litter where they spend the winter. A photograph of the larvae may be found on the Internet at: http://texasforestservice.tamu.edu/main/popup.aspx?id=1191.

gilmermirror@gmail.com