These may look like caterpillars, but they are not. They are sawfly larvae, specifically redheaded pine sawflies. Sawflies are the larvae of a specialized group of plant-feeding wasps. Redheaded pine sawflies feed on the needles of several species of southern pines, often focusing their attacks on sapling-sized trees, up to 12 to 15 feet tall, in home and commercial landscapes, as well as in commercial pine plantations. They sometimes defoliate areas of several acres or more in young pine plantations. Trees will recover from this defoliation, but it will slow growth. The greater problem in ornamental settings is that severe sawfly defoliation makes trees look unsightly for a while. Here in the South there are about three generations per year, but outbreaks are sporadic because populations are often controlled by beneficial organisms that feed on the larvae.
Control: Treatments are usually only justified/practical on small, recently planted trees in home or commercial landscapes, trees that would be unsightly and suffer retarded growth if sawflies were allowed to defoliate them. Sawfly larvae are susceptible to many insecticides and are easily controlled with foliar sprays, but you have to react quickly if you are going control the sawflies in time to prevent heavy damage. Insecticides that contain the active ingredient spinosad (Fertilome, Monterey, Bonide, and Greenlight all make such products) are recommended because these are less likely to trigger secondary outbreaks of spider mites or other pests than treatments containing ingredients like carbaryl, acephate, or pyrethroids (bifenthrin, permethrin, cyfluthrin, etc.). Conserve (spinosad) is a good option for commercial applicators.
See page 21 of Extension Publication 2369, Insect Pests of Ornamental Plants in the Home Landscape, for more information.
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Blake Layton, Extension Entomology Specialist, Mississippi State University Extension Service.
The information given here is for educational purposes only. Always read and follow current label directions. Specific commercial products are mentioned as examples only and reference to specific products or trade names is made with the understanding that no discrimination is intended to other products that may also be suitable and appropriately labeled.