Late sign of damage. Larvae tunnel into the center of new shoots, causing the needles to turn red and die. As the shoot elongates, the dead tip becomes more obvious and looks much like frost damage.
Damage tends to be heaviest in even years.
The sawflies overwinter as either larvae or pupae in earthen cells in the soil. Adults, which emerge in early spring, lay eggs through the bud sheath before buds swell. Upon hatching, the young larva feeds toward the tip of the shoot in the needle cluster. Later, it burrows into the shoot and tunnels towards its base. In more northerly regions, the insect may spend nearly two years in the cocoon.