European Crane Fly

European crane fly larvae are large, wrinkled, grayish-brown maggots that feed on grass roots and organic matter in moist soils across Western Washington. You will see adult flies, which resemble giant mosquitoes but do not bite, emerging in fall and winter. Larvae damage turf and young plant roots, creating bare patches and wilting. Damage is most severe in wet years and poorly drained sites.

Improve soil drainage through aeration and amendment to reduce pest habitat; crane fly larvae require very wet conditions. Allow beneficial parasitoid wasps to establish in turf; they parasitize larvae effectively. No broad-spectrum insecticides are recommended; the pest pressure in home settings is usually tolerable. Accept some turf damage as a cost of growing grass in wet climates. Overseed damaged areas in spring after soil dries.