The larvae of the European cranefly feed on the crowns of grasses during the winter and spring. Damage can be severe in lawns, appearing as large patches of dead or dying grass. The grass usually recovers when the larvae stop feeding, but weed invasion may occur in the weakened areas. Adult craneflies are mosquito-like with long legs. The body is about 1" long. They emerge from lawns and pastures in late August through September and may gather on the sides of houses in large numbers. Eggs are laid in the fall. The full-grown larvae are about an inch long, gray-brown, and worm-like with a tough, leathery skin which gives them the common name "leatherjackets". They feed in the soil from fall through spring, pupating in the summer. They feed primarily at night and during cloudy weather on overcast days. Treatment is usually not necessary unless spring sampling indicates numbers in excess of 25/square foot. Also, well-established lawns that are properly irrigated and fertilized rarely need treatment even at numbers higher than this.

Management Options

Non-Chemical Management

Starlings, robins, and many predacious insects often feed on crane fly larvae in lawns reducing numbers of crane fly larvae to below damaging levels by spring.
Sample several areas of the lawn to determine if there is a problem before making any chemical applications.

Select non-chemical management options as your first choice!

Chemical Management

IMPORTANT: Visit Home and Garden Fact Sheets for more information on using pesticides

If you suspect that you have a cranefly problem, it is important to determine the level of cranefly infestation. Monitor the lawn in February/March and consider treatment if larval numbers exceed 25-30 per square foot. If you have had serious previous infestations or missed the spring application, monitor larval populations in mid-November to December when larvae are about 3/8-inch long. If populations exceed 25-30 at that time, then treat. Note: Do not treat in the fall if an effective treatment was made in the spring. Two applications per year are unnecessary. Many pyrethroids are toxic to bees. There is no data currently available on the bee toxicity of cyfluthrin, a pyrethroid registered for lawn use. Be cautious and mow or remove weed flowers before applying.

Listed below are examples of pesticides that are legal in Washington. Always read and follow all label directions.

Safer Brand BioNEEM Multi-Purpose Insecticide & Repellent Conc [Organic]
Active ingredient: azadirachtin | EPA reg no: 70051-6-42697
This list may not include all products registered for this use.

Images

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Caption: European cranefly damage on lawn Photo by: C.R. Foss
Caption: European cranefly damage on lawn Photo by: A.L. Antonelli
Caption: European cranefly larvae Photo by: A.L. Antonelli
Caption: European cranefly female adult Photo by: A.L. Antonelli

WSU Extension

Hortsense