Redheaded Pine Sawfly

The most damaging sawfly in Texas is the redheaded pine sawfly, Neodiprion lecontei. Sawflies are a diverse group of insects that defoliate hardwood and coniferous trees in the U.S., and several are native to Texas.  

Contrary to their name, sawflies aren’t true flies. They belong to the Hymenoptera family, along with bees and wasps, although they cannot sting. 

The redheaded pine sawfly is a significant defoliator of young southern yellow pines, primarily those less than 15-20 feet in height. The redheaded pine sawfly is particularly damaging to young pine plantations, and occasionally to ornamental trees. Outbreaks in young plantations can spread over large areas and may persist for several years. 

They have caused increased concern in recent years, possibly due to the establishment of more pine plantations.  

Life cycle

Sawflies get their name from the saw-like ovipositor (egg-laying structure) on the end of the female’s abdomen. The ovipositor is used to lay eggs in small slits she cuts with it in pine needles.  

The adult, or wasp, stage of the sawfly is seldom seen and causes minimal damage to plants when the female deposits her eggs. It is the larval stage that consumes needles and causes damage. 
 
Sawfly larvae don’t have the typical grub-like appearance of most wasp larvae. At first glance, they resemble the caterpillar of a moth or butterfly. The easiest way to distinguish sawfly larvae is by their over five pair of fleshy legs on the abdomen and only one eye on each side of the head. Moth and butterfly larvae have five or less pair of fleshy legs and six eyes on each side of the head.  
 
Females deposit 100 or more eggs in rows of slits they saw in the edges of needles. Usually, one egg is laid in each slit. Even if the female has not mated with a male, the eggs are living. Fertilized eggs produce both male and female offspring and unfertilized eggs produce only females. 

 Larvae emerge from the eggs in 15 to 30 days and begin to feed in groups on the pine needles. They usually feed 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. Small trees that are completely defoliated seldom live.  

While they feed, air temperature also determines how quickly the larvae develop. The cooler it is, the longer development takes. When weather conditions are warm, as many as five generations may be produced in one year. 

The sawflies overwinter in a dormant larval stage, change to pupae in early spring, and emerge as adults a few weeks later. Some individuals remain in the dormant larval stage until the second spring before they pupate and emerge as adults. This allows some sawflies to survive if most of the current generation dies. 
 
Full-grown larvae are about one inch long . They have a rust-red head and a hairless, yellow-white body with six rows of black dots. If sawfly larvae are disturbed, they have the characteristic habit of curling the forward third of their body backward, presumably as a defensive measure to scare enemies. When the larvae are mature, they drop to the ground and spin a tough, egg-shaped cocoon in the soil or litter where they spend the winter.  

Redheaded pine sawfly are controlled by several natural factors. Populations may decline rapidly due to adverse weather, especially in the early spring. Also from parasites, predators, virus diseases, and rodents that feed on pupae.  

Several methods of control have been developed for sawflies over the years. Sawflies prefer some shade, so the most important control is to keep the plantation mostly free of overshadowing hardwoods.  

When chemical control of sawflies is warranted, Orthene or Sevin can be used. Sprays should be applied to the foliage as soon as an infestation is observed. Since several generations may occur in a year, suspected areas should be checked throughout the summer for possible infestations.  
 
All suggested chemicals must be registered for use on sawflies by the U.S. Environmental Protection Agency and the Texas Department of Agriculture. Before using any pesticide, read and carefully follow all application directions, cautionary statements, and other information on the label.