Because it has two generations per year, all the needles on a pine can be eaten in a single season. The spring generation can strip trees of their older needles and the summer generation can strip off the current year's needles. This total defoliation can result in death of the pine. This sawfly is found from Southeastern Canada through the eastern United States. Norway spruce, Deodar cedar and larch, especially if near its preferred pine hosts.
Larger larvae eat the entire needle down to the sheath.
The larvae are strongly gregarious, feeding in groups of 100 or more. Usually one year old foliage is eaten but all foliage may be eaten on heavily infested plants. If a tree is entirely defoliated before the larvae are mature, they will migrate to the nearest conifer. This is when they may attack non-preferred hosts. Severe defoliation may kill plants while light defoliation will result in unsightly trees.