There are three or four generations each season and the insect winters in the soil in the pupal stage. It emerges in April or May and lays white cylindrical, netted eggs in clusters of from two to five on the underside of a leaf. They hatch in 4 to 6 days and the young maggots enter the tissue of the leaf where they make first thread-like mines, and then blotches which may eventually coalesce to involve the entire leaf. If food becomes exhausted, they migrate to other leaves. Row covers can be used to keep the flies away from the plants, but the area planted must have been free of both cultivated and weed hosts in the previous year.
Deep spring plowing can destroy overwintering leafminer pupae.
Spinach grown late in the fall, over the winter, and very early in the spring may escape injury. The gardener can find and crush the eggs on the leaf and remove leaves with mines and destroy them. Malathion is among the compounds registered for control of this pest in Connecticut. Chemical control must be directed at the adults, since larvae are protected from insecticides inside the leaf. Consult the label for dosage rates, safety precautions, and observe the long required interval from application to when the spinach may be harvested.