–by Dr. Raymond Cloyd, Professor and Extension Specialist in Ornamental Entomology/Plant Protection
European pine sawfly, Neodiprion sertifer larvae are out-and-about feeding on pine trees. Young larvae are 1/4 inch in length and olive-green in color with a black head (Figures 1 and 2).
Older larvae are >1.0 inch long with green stripes. The larvae are gregarious or feed in groups on the needles of a variety of pines, especially Scotch, red, and mugo pine. Larvae will strip the needles of mature foliage, leaving only the central core, which is white and then turns brown (Figure 3); eventually falling off.
In general, larvae complete feeding by the time needles emerge from the candelabra. Therefore, those needles are not damaged. There really is only a minor threat of branch or tree death resulting from sawfly larval feeding. However, the loss of second- and third-year needles may be noticeable in landscape trees and ruin their appearance. In late spring, the larvae drop to the ground and pupate in brown, leathery cocoons at the base of trees. Wasp-like adults emerge in fall and lay eggs in the needles before winter. There is one generation per year in Kansas.
Although sawfly larvae look-like caterpillars; they are not caterpillars (Order: Lepidoptera) as they are related to ants, bees, and wasps (Order: Hymenoptera). The best way to tell a sawfly larva from a caterpillar is by the following: 1) sawfly larva have prolegs on every abdominal segment whereas caterpillars are missing prolegs on the abdomen and 2) caterpillar larva have hairs or crochets on their feet whereas sawfly larva do not have hairs or crochets on their feet.
Since sawfly larvae are not caterpillars, the bacterial insecticide, Bacillus thuringiensis subsp. kurstaki (sold as Dipel) will not directly kill sawfly larvae. Therefore, dealing with sawfly larvae involves hand-picking (you can wear gloves if you wish) or dislodging larvae from plants by using a forceful water spray. If necessary, there are a number of insecticides that may be applied to suppress populations of the European pine sawfly including acephate (Orthene), azadirachtin, carbaryl (Sevin), spinosad (Captain Jack’s DeadBug Brew and Conserve), and any pyrethroid-based insecticide with any of the following active ingredients: bifenthrin, cyfluthrin, and lambda-cyhalothrin). Be sure to read the insecticide label to make sure that sawflies are listed. For more information regarding European pine sawfly management contact your county or state extension specialist.