See Apple for a detailed discussion of these diseases. Insect Problems Mountain ash sawfly, Pristophora geniculata .
Young larvae are greenish white, with black head and legs and black dots on the body.
The adult sawflies emerge late in the spring. Larvae feed during the summer and drop to the ground to pupate over the winter. There may be a partial second generation. Spray the larvae with either carbaryl, malathion or Spinosad, which are among the compounds registered for control of this pest in Connecticut, when they are feeding. Consult the label for dosage rates and safety precautions.