Pear Slug (Cherry Slug or Pear Sawfly)
Overwinters as a sawfly pupa in the soil. Adults lay eggs on leaves in mid summer. The larvae have a slug-like appearance and feed on the upper surface of the leaf epidermis creating "windowpanes."
They cause a skeletonizing injury where membranous “windows” of leaf tissue remain in between leaf veins. Leaf feeding injury can proceed rapidly when populations are high.
Watch for sawfly larvae starting in mid to late July.
No threshold determined.
Degree Day Model
The larvae are often suppressed by insecticides applied for other pests. Trees can tolerate low populations.