This tiny fly or midge overwinters as an adult. When new growth begins, the female lays eggs in the young leaflets. Larvae hatch in one or two days and begin feeding. Their feeding causes the leaflet to become a pod-like gall that frequently dries up and drops prematurely. Small branches may die back but new shoots grow from the base of the dead twig.
Many generations occur in a year.
Control involves several methods. Avoid planting 'Sunburst,' which is particularly susceptible. Carbaryl or spinosad, which are among the compounds registered for control of this pest in Connecticut, can be sprayed on the foliage in mid-May. Consult the labels for dosage rates and safety precautions.