During the first two weeks in September, you may see adult crane flies. They are getting ready to lay eggs in moist soil in low areas. While adults don’t damage plants directly, their larvae, called “leatherjackets,” do. Larvae live underground from early October to the following September. During these months, these grey, legless maggots, with finger-like appendages on the posterior end and no well-defined head, cause damage to crowns and roots of turf grass.

Key points about crane flies:

• There is no need to do anything to the adult crane flies in the fall. They have probably laid eggs and will soon die.
• If you are concerned about crane fly damage, November, December and January is when to act. Check for larvae in holes near bare or dying spots in the lawn, where water pools on the surface and soil is saturated. If digging in several spots exposes larvae, cut up a square foot of lawn and count their number to assess the population.
• Healthy turf care is the best defense. Use proper mowing, irrigation and fertilization for lawn care. Improve drainage in low spots. A strong turf can co-exist with under 25 leatherjackets per square foot of turf. See resources below for other options.

Managing Crane Flies in Lawns: https://extension.oregonstate.edu/catalog/pub/em-9296-managing-crane-fly-lawns

Practical Lawn Care for Western Oregon: https://extension.oregonstate.edu/catalog/pub/ec-1521-practical-lawn-care-western-oregon

Crane Flies – those funny-looking insects that might (or might not) be lawn pests https://s3.wp.wsu.edu/uploads/sites/2053/2012/11/90CraneFlies.pdf

---

Click here for a printable pdf of this article. Written by Jane Collier, August 2024