European Pine Sawfly

Now is the time to inspect mugho, Scots, red and other pine trees and shrubs for clusters of defoliating gray-green "worms."

The European pine sawfly is a common problem during the month of May. Larvae of this widespread pest are grayish-green with 2 light stripes and 1 dark stripe on each side of the body. The legs and head are shiny black. Full grown larvae, usually present by Memorial Day weekend, are about 1 inch long.

European pine sawfly larvae are gregarious and stay together in a cluster as they feed on the old needles from pine trees and shrubs. Because only old needles are eaten and not the new, emerging growth, defoliated trees are generally not killed. Damage may be aesthetically displeasing, especially in Christmas tree plantations, and growth of the tree may be stunted.

Control can be as simple as pruning off and discarding infested branches. Heavier infestations on larger trees may justify foliar sprays of horticultural oil, insecticidal soap or a contact insecticide such as Sevin. Spraying is of greatest benefit when done before the larvae become one-half grown. Late sprays, after larvae are full-grown, are usually not warranted.

This article originally appeared in the 5/4/2005 issue.

Issue: 
Category: 
Authors: 

Links to this article are strongly encouraged, and this article may be republished without further permission if published as written and if credit is given to the author, Horticulture and Home Pest News, and Iowa State University Extension and Outreach. If this article is to be used in any other manner, permission from the author is required. This article was originally published on May 4, 2005. The information contained within may not be the most current and accurate depending on when it is accessed.