European Pine Sawfly
The European Pine Sawfly attacks two and three needle pines, including Scotch, Austrian and Mugho. These trees should be monitored beginning in mid April for the first sign of infestation which is rows of yellow eggs on the needles.After hatching, the larvae may be seen feeding in clusters. They are translucent green with dark heads and may initially be hard to spot on the needles because they match the needles so well. Several hundred may work together, and after demolishing one twig move on to the next. When disturbed, they move in uncanny unison, elevating their rear ends. Eventually, the needles become dry, curled and straw-like or are completely eaten down to the stubs.
The Sawfly adult is about 5/8 inch long and black to brown.It resembles a wasp or bee. The mature larvae are about one and one-quarter inches long and are grayish green with a light stripe down the back, two white lines bordering a broken stripe of intense green. There are one or two generations per year. Prepupae overwinter in brown cocoons in the duff or in the soil.
The females lay rows of eggs in needles, causing yellow spots to form. After hatching, the larvae feeding is confined to old needles; infested ornamental pines will show, by the end of May, new green plumes waving at the end of long, naked branches. Clusters of larvae often defoliate branches and in heavy infestations, entire trees may be stripped. Look for the clusters of larvae near the defoliated twigs and branches.
Light infestations on small pines (such as Mugho), may be hand- picked and destroyed.
Formulations of many insecticides are labeled for Pine Sawfly control.* Ideally, infested trees should be treated when the larvae are small and first observed (late April-early May). Follow all label directions for specific information on host plant label clearance, phytotoxicity information, safety precautions and dosage information.
* See Woody Ornamental Insect, Mite and Disease Management, The Pennsylvania State University (2005) for more details.
WARNING: Pesticides are poisonous. Read and follow directions and safety precautions on labels. Handle carefully and store in original labeled containers out of reach of children, pets and livestock. Dispose of empty containers right away , in a safe manner and place. Do not contaminate forage, streams or ponds.
For professional assistance with tree and shrub problems contact a Keystone arborist
Penn State Fact Sheet on European Pine Sawfly