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. Iowa State University , Ames, Iowa. This information subject to a usage policy .