Wounds, such as this one caused by trellis wire, provide entry points for the apple clearwing moth.
The flight of adult clearwing moths begins in early June in British Columbia, Canada. Females visit flowers in the orchard and feed on nectar for a few days before laying eggs.
Trees on Malling 9 or M.26 often have burr knots that make good entry points for the larvae. Moths also lay eggs in wounds on other parts of the tree, such as pruning scars, grafts, or wounds caused by trellis wires.
Larvae that hatch from the eggs burrow under the bark and spend almost two years in the tree feeding on the cambium layer before emerging from their galleries to pupate. As they pupate, they protrude from the bark, and the pupal cases are left on the tree as they emerge as adult moths.
A telltale sign of infestation is red frass that the larvae push out of the tree
SOURCE: Dr. Gary Judd, Pacific Agri-Food Research Centre,
Summerland, British Columbia, Canada