Sawflies, closely related to bees and wasps, that also commonly feed on birch trees.
Wood boring insects on willow trees feed in both their larval and adult stages. During the end of spring and throughout summer, adults feed on new willow growth and chew holes into bark near the soil line into which they lay their eggs. Within two weeks, the larvae hatch and tunnel into the trunk or soil. Unfortunately, growers may not notice the problem or may think damage is associated with other pests like woodpeckers.
Larvae tunneled into the lower trunk of trees. Trees may become malformed. Look for holes as well as a residue that resembles sawdust as a sign of borer infestation. Adult damage includes the death of shoots that often fall to the ground.