European sawfly attack pine trees and shrubs including mugo pine, scots pine, red pine, jack pine, and Japanese red pine. When searching for signs of this pest, look for yellowing of needle clusters which have been skeletonized by feeding young larvae. Old foliage may be consumed, but new needles develop normally leaving a “bottle brush” appearance. The host tree or shrub may have a stunted look to it. The 1/8"-1" long, caterpillar-like larvae are grayish-green and have a light stripe down the back and a light stripe along each side followed by a dark green stripe. The heads are shiny black. The eggs hatch in late April to mid-May and larvae feed until mid-June. By mid-June larvae drop to the ground and spin brown cocoons in the leaf litter at the base of the host. Adults emerge from the cocoons late in August through October. Females create slits on the edge of the needle and lay eggs by inserting them into the slits, where they remain all winter until egg hatch. Depending on the weather, the sawfly may have one to two generations per year.
Depending on the species of the host plant a preventative fall or spring soil injected pesticide is extremely effective in controlling small larvae. Foliar applications can also be expected to yield acceptable results, provided applications are timed with relatively small larvae sizes. Once mid-summer is reached and larvae are large, control is more difficult to obtain.
Contact Plant Health Solutions for proper diagnosis and to develop a treatment plan.