The legs and head are shiny black. Full grown larvae will be about 1 inch long. The larvae are gregarious and stay together in a cluster as they feed on the old needles from mugho, Scots and red 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 Sevin, Orthene or Isotox. Iowa State University , Ames, Iowa. This information subject to a usage policy .