Right now is the time to check pine trees for European Pine Sawfly larvae. These grayish-green "worms" feed in clusters on the old needles of mugho, Scots and red pine trees and shrubs. Each larva has 2 light stripes and 1 dark stripe on each side of the body. The legs and head are shiny black. Full-grown larvae will be 1 inch long by Memorial Day weekend. Then they will disappear for another year.
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, Sevin, Orthene or Isotox. 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 May 14, 1999 issue, p. 57.
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