Spray should be directed from the bottom of the plant upward to ensure thorough coverage of the lower leaf surfaces. Imidacloprid, applied as a systemic to be taken up by the roots, will also provide season-long control. Consult the labels for dosage rates and safety precautions. Hawthorn leafminer, Profenusa canadensis . This sawfly overwinters in the soil as pupae.
Adults emerge just as hawthorns are beginning to leaf out.
Eggs are laid singly in the upper epidermis where the petiole and leaf blade meet. After hatching, the larvae feed on inner leaf tissue, moving along the leaf margin toward the tip. There may be multiple larvae per leaf. In mid-June they cut a hole through the lower epidermis and drop to the ground to pupate. There are two wasp parasites that may provide control.