Key Features
- Missing old and young needles
- Groups of white, black-spotted larvae
Symptoms
Groups of black and white, worm-like larvae can be seen feeding on old and young foliage in June and September. Larvae completely consume old and young needles. Complete defoliation will kill the tree. Sawflies are most commonly found on white pines, but occasionally feed on red pines. A closely related species is the red headed pine sawfly that has two generations a year and a red head.
Biology
Sawflies are stingless wasps that lay eggs in leaf tissue with a saw-like tail. Adults emerge from the soil in the spring and lay eggs in needles. Eggs hatch into worm-like larvae in June and feed in groups on old and young needles. After larvae become about 1" long, larvae make brown bullet shaped cocoons (1/2" long) that can be found along the trunk or on the ground. They have one to 2 generations a year. The photo of feeding larvae was taken on September 24, 2001 in Indiana.
Management Recommendations
Complete defoliation, or repeated defoliation, can kill the tree. Inspect thin branches for groups of worm-like, white larvae. To control sawflies without promoting later season problems with scale insects use biorational products such as spinosad, chlorantranilioprole, indoxacarb, neem oil, insecticidal soap or horticultural oil. Products are most effective when applied to young sawflies, when found feeding in the early or late summer generation. After sawflies are one inch long, they stop feeding and drop to the ground to where they build cocoons and transform into adults. Applications of insecticide at this time are no longer needed as feeding has stopped.
Effective Pesticides
Active Ingredients include: Acetamiprid, Bifenthrin, Carbaryl, Chlorantraniliprole, Horticultural oil (Paraffinic or superior oil) , Indoxacarb, Insecticidal soap (Potassium salt of fatty acid), Neem oil, Permethrin, Spinosad
