European Pine Sawflies noted in Norwood

Guest blog by Donna Laake

Imagine leaving your home in the morning with all of your bushes and plants green and in bloom only to come home a few hours later to find 3 large pine bushes that were over 30 years old completely devoid of their pine needles. That’s what happened recently to a Norwood resident last week who educated me about an infestation of European Pine Sawflies. As a member of the Norwood Tree Board, I had never heard of such a thing, but with a little detective work, I soon became aware of these pests and the damage that can be done by them.

The European Pine Sawfly is the most common sawfly that infests pines in Christmas tree plantations, home and nursery plants. The larvae look similar to caterpillars but are most wasp-like. The flies prefer mugho, Scotch, red, Jack and Japanese pines, but sometimes will feast on white, Ponderosa and other pines. Larvae eat only the surface of the pine needle, causing it to turn brown and wilt. As they grow, the larvae stick together and feed from the tip of the pine needle to the base. The larvae feed on the older pine needles, moving from branch to branch, leaving the newer growth untouched. They are voracious eaters! Larvae will move from tree to tree/bush to bush as needles from their previous host are devoured, leaving some bushes or trees completely without any needles. Trees or bushes sometimes can survive because the European Pine Sawfly does not eat new growth.

The European Pine Sawfly spends the winter as an egg on the pine needle, hatching in April to mid-May and feed until mid-June. Larvae are about one inch long and are green with a light stripe down the back. As they mature, the larvae drop to the ground and spin a cocoon. Adults emerge in August and September to mate and lay six to ten eggs on needles, preparing for the next round of eating.

So how do you control these pests? If you can find the eggs on the branches before they hatch in the spring, the eggs can be removed by hand….doesn’t sound too promising to me. You can cut off the affected branches and place them into a plastic bag to destroy. Sometimes the larvae can be knocked off the branch and placed into a pail of soapy water to kill the larvae. And then there are always the insecticide sprays for infestations that are larger.

Bottom line, check your pine bushes and trees in late winter or early spring for signs of these pests. I’ve been told that once the European Pine Sawfly is spotted in an area, bushes and trees within a 5 mile radius are at risk. For more information and pictures of the European Pine Sawfly, go to the O.S.U. Extension website at http://ohioline.osu.edu/hyg-fact/2000/2555.html or just Google “European Pine Sawfly.”

Donna Laake
Norwood Tree Board