Crane flies

Asked October 6, 2014, 9:45 PM EDT

Because the dispensation of spray to treat crane flies varies in Washington from either fall or Feb/Mar, how do I determine which type of fly has infested our lawn? One company says spray next month (Oct.) another says they do their crane fly spraying after the 1st of the year. We know the larvae are what does the damage and want to be sure the cost and application of spraying will be effective. How do we determine which type of fly (European or "regular") we have?

Clark County Washington

1 Response

From HortSense: at
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
Select Non-chemical Management Options as Your First Choice!!
  • Sample several areas of the lawn to determine if there is a problem before making any chemical applications.
  • 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.
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.
    If you choose to use a pesticide, some examples of products that are legal in Washington are listed below.

    Always read and follow all label directions.
  • Bayer Advanced Garden Power Force Multi-Insect Killer R-T-S
  • Ortho BugBGon Max Lawn & Garden Insect Killer I Conc
  • This list may not include all products registered for this use.