European Crane Fly
Tipula paludosa
6 host plants
Last updated
European crane fly larvae are large, wrinkled, grayish-brown maggots that feed on grass roots and organic matter in moist soils. 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.
Quick Reference
Monitoring & Action
Pull back brown turf in February-March and count larvae per square foot. Threshold: 25+ larvae per sq ft warrants treatment; below that, turf can outgrow damage. Soap flush (flush method) forces larvae to surface for counting. Distinguish crane fly damage from compaction, drainage, or shade stress - these are more common causes of winter/spring lawn decline in Western Washington.
25+ larvae per square foot in maintained lawns; 15+ in high-value turf. Below this threshold, healthy turf can outgrow damage without intervention. Most lawns showing brown patches in February-March are below threshold. Confirm presence and count before treating.
Cultural Controls
- Maintain dense, healthy turf through proper mowing height (3 inches), overseeding bare spots, and improving drainage. A thick stand of grass outcompetes whatever feeding pressure larvae create. This is prevention, not treatment.
- Apply beneficial nematodes (Steinernema feltiae) when soil temperatures exceed 42°F and soil is moist. October or early March are the best windows. Nematodes parasitize larvae in soil zone.