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What to do? (Treatment) 

Some treatment options for you. Please also contact your local Master Gardener for advice.

Do-Nothing

A healthy lawn will easily recover, even when the population of leatherjackets is high. Watch weeds if sparse patches appear and reseed if necessary.

Leatherjacket populations can decrease as much as 50% during winter months and between March and May because of predators and natural causes.

Cultural Management of Crane Flies

Grow lawns where lawns do best. Only establish turf in sunny locations. Shade can reduce vigor and promote the survival of crane fly larvae. In areas of low sun, consider a turf alternative groundcover.

Remove excess thatch. Thatch is that layer of old dead grass stems that builds up and reduces the availability of nutrients and water if it gets too thick. Having thatch is good but too much provides a nice environment for crane fly larvae. In fact, just below the thatch is where you can find most crane fly larvae feeding.

Aerification cuts and brings to the surface soil and root cores that then reintroduces oxygen into the soil, which results in stimulating root development. Aerification also improves the movement of water and nutrients into the soil.

Mow your lawn regularly. The correct mowing height is a function of the type of grass species in your lawn. During the summer, mowing every week or so is needed, as you never want to remove more than 1/3 of the total grass blade length. Waiting longer between mowing and removing more of the grass blade weakens the grass. When you mow, leave the grass clippings on the lawn, as they provide a safe source of recycled nutrients and thereby reduce the need to additional fertilizer.

Lawns do need some fertilization, although not as much as is sometimes applied. Mulching your cut grass clippings directly on the turf also reduces this need as well.

Let your lawn go dormant during the dry months. Crane flies are actually semi-aquatic insects and enjoy a moist environment. Dry soil conditions in late summer and early fall may increase crane fly mortality.

If watering is required, it should de done infrequently but sufficiently long enough duration so to wet the entire root zone. This means applying about one to 11/2 inches of water every four to six days and nothing in-between. These infrequent but deep waterings build deep and strong root systems that tolerate crane fly damage.

Keep your lawn well drained. In areas where the soil is saturated by water most of the time, consider planting something other than turf.

Biological Control of Crane Flies

Encourage birds to visit your yard, especially in the winter and spring months. Bird predation can reduce a heavy population of crane flies to just a few larvae in a short time.

Reduce the amount and frequency of all pesticides (herbicides, fungicides and insecticides) in your yard. Predaceous ground beetles feed on crane fly larvae (along with many other pests too).

Chemical Management of Crane Flies

If you've sampled your lawn and know that you're one of the few with an actual crane fly problem, you may decide to arm yourself with a pesticide. Be sure the chemical is legal for home use on lawns. Information regarding chemical treatment of crane fly can be found on the WSU Hortsense. Follow use, storage, and disposal directions on the label. It's the law.

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In this article...

Introduction

Crane Fly Sampling

Decision-Making

Treatment Options




See also:

Crane Fly Identification

Native Crane Fly Identification

Crane Fly Calendar

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