Tree insect problems

Defoliators – pine sawflies

5. Pine sawflies

Can be found in Ponderosa, Scotch, Austrian, and Jack Pine trees.

Sawfly larvae have eight pairs of prolegs and vary in color from grayish- to yellowish- green. Some species have one or more longitudial stripes. Mature larvae may reach 18 to 25 mm in length. Adult sawflies resemble small bees.

The life cycle and number of generations varies with the sawfly species. Most species over winter as pupae or prepupae, a few as eggs. In spring larvae usually feed in groups on needles, starting at the needle tip. Older larvae feed singly or in pairs, but usually on the same branch as other larvae. The larvae of most species drop to the ground, spin cocoons, and pupate in the soil. All larvae rear up in a characteristic “s” -shape when disturbed.

Some species characteristically feed on young needles, others on old needles, and still others on both young and old needles. Species that feed only on old or young needles weaken trees and slow their growth, while species that feed on both young and old needles may kill severely damaged trees.