Apple sawfly

Overview

When apple trees are in flower, the sawfly, Hoplocampa testudinea, lays its eggs in the developing fruit. In June, the larvae tunnel their way under the skin of the fruit and into the core, causing the apples to fall. When they're ready, they tunnel out of the apples, creating a second hole, and then bury themselves in the soil to pupate. Sometimes the larvae die and don't make it to the middle of the apple, in which case the apples mature, but they'll have ribbon scars and are sometimes misshapen.