There are several species of sawflies that attack Mugo and Scots pines including the redheaded pine sawfly and the European pine sawfly. Both can be especially troublesome. Because they have 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. The first instar (newly hatched) larvae strip the needle surface leaving straw-like remains. Larger larvae eat the entire needle down to the sheath. The larvae are strongly gregarious, feeding in groups of 100 or more. Severe defoliation may kill plants while light defoliation will result in unsightly trees. Spray treatments are effective.