Little green worms

Q. What are these little green worms? I found them on my pine tree.

Nancy from Boardman

A. This is a common invader here in the Valley. Stephanie Hughes, one of our OSU Extension master gardener volunteers, saw the same insect in her yard this past week. Below is her description of this insect and its damage:

While walking in my yard inspecting my plants, I came across the European pine sawfly larvae having a banquet on my pines. The favorite diet is Mugo, Scotch, red, Jack, and Japanese pines. These larvae (not caterpillars) originated in Europe. The first hatchlings, or instars, eat the needle surface, giving the needles a brown and strawlike appearance. These larvae remain together, feeding from tip to base of the needles, eating the older needles, until the whole branch is stripped. As new growth develops, the tree takes on the characteristic “bottle brush” appearance. The tree will survive. They can migrate from limb to limb and tree to tree as food sources become depleted.

Eggs are laid in slits in needles’ edges, and they hatch from mid-April to May, when the larvae begin to feed until mid-June. They are greyish-green with a light stripe down the back and sides, and shiny black heads. The defensive move is a group raising their heads and tails to threaten, looking like a wave.

When mature, they drop to the ground and spin tough fibrous brown cocoons. Adults emerge in late August to September to mate and lay eggs. Each female lays six to eight eggs per needle on 10 to 12 needles.

If inspection of trees shows the larvae and their damage, control may be necessary. Natural parasites can control, but may not be adequate. You can remove the eggs, but they need to be destroyed, not just thrown to the ground. You can remove the colonies by clipping the infected branches, placing them into a plastic bag and destroying them. You can crush them or place them into hot soapy water.

Spraying with summer or verdant oils and insecticidal soaps can help, if they are labeled for sawflies on ornamentals. Thorough coverage is necessary. Insecticides are available for dealing with colonies in home landscapes. Be sure to read and follow all label directions.

Control of these invaders is necessary to prevent overwhelming infestations from harming your landscape plants as well as your neighbors’. Control is best achieved when larvae are small. To read more and see photos of this insect, go to: http://go.osu.edu/sawfly.

Eric Barrett is OSU Ext. educator for agriculture and natural resources in Mahoning County. Call the office hot line at 330-533-5538 from 9 a.m. to noon Mondays and Thursdays to submit your questions.