From the Desk of Ed Hume: European Crane Fly

June 21, 2010 at 8:02 AM Leave a comment

The damage from the European Crane Fly has just ruined the appearance of lawns in some areas of the Pacific Northwest.  Evidence of the presence of this pest is noted by bare spots or yellow patches of grass in the lawn.

In the springtime the European Crane Fly is in the larvae stage and is grayish-brown in color and worm-like in appearance.  The larvae are quite large, about 1 1/2 to 2 inches in size and have a tough skin.  It’s for this reason that it is commonly called “leatherjacket.”

The European Crane Fly (Tipula paludosa) has been invading the Puget Sound region from the North.  This pest has been quite active in British Columbia and Northwest Washington for the past few years and each year is migrating further to the South.  The presence of the European Crane Fly has been especially noticeable in the Peninsula and to the East of Puget Sound and into Oregon.  The damage is spotty in some areas and very heavy in others.

The “leatherjackets” can devastate a lawn in just a matter of days.  They’re most often found in areas where there is poor drainage or where there is moderate to heavy build-up of thatch in the lawn.  The “leatherjacket” stays underground during most of the day, however it is not unusual for them to surface and feed on above-ground parts of plants on a damp, warm night.  If you’re in doubt as to whether your lawn is infested with the European Crane Fly, Dr. Art Antonelli, entomologist at the Washington State University Research and Extension Center in Puyallup, suggests that you examine the lawn at night by flashlight or take a core sample from the area where you suspect an infestation.

In areas of heavy infestation where the lawn is quite bare, the larvae will be found deeper in the soil than in spots where some green grass remains.

It should be noted that in most infested areas only about one in ten lawns is infested by crane fly larvae.  Be sure to examine your lawn carefully and be certain the insect is present before spraying.

European Crane FlyIn the adult stage, the European Crane Fly looks much like an oversized giant mosquito.  The adult fly emerges from the soil anytime from early August through September.  Then during a 24 hour period after emerging they will mate and lay eggs in the grass. During the Fall, the eggs hatch and the larvae begins feeding on the root crown of turf grass.  They Winter-over and in March, April, and early May as the weather warms they continue to feed and it is at this time they are most evident because of the damage they cause.

The larvae remains in a non-feeding pupae stage just below the soil surface during June, July, and August.  Then the pupae wiggles to the surface and the adult Crane Fly emerges, thus the cycle starts all over again.

It is not unusual for the large adult Crane Fly to gather on the side of the house in late Summer or early Fall.  This is of concern to the homeowner, but keep in mind that the fly does no damage to the house and the Crane Fly does not bite or sting.

At this time of the year when the Crane Fly is in the larvae stage, it doesn’t seem to be an attractive food for birds.  This is probably due in part to the fact that they develop a tough skin.  Yellowjackets, however, do seem to prey on them and will often be found prowling the lawn looking for emerging Crane Fly.

The best time for controlling the European Crane Fly is in the Spring.  The spring application is generally made from mid-March through late April or whenever the larvae (worm) are present.

In the past, both Diazinon and Dursban were the insecticide recommended for the control of the European Crane Fly.  Now both are in the process of being banned, so ‘Delta Eight’ by Bonide is a better choice because it is more environmentally friendly.

It seems that cool temperatures or wet soil conditions sometimes reduce the effectiveness of insecticides.  When possible, apply on a warm day at a time when the soils are drier.

When this article was originally written, Dr. Roy Goss, (now retired) agronomist from the Washington State University Research Center in Puyallup, suggested that renovation of a lawn damaged by Crane Fly should start with power raking to remove the thatch.  After that, over-seed the lawn with a mix of 50% fine fescue and 50% rye grass, using 3 to 4 pounds per one thousand square feet of lawn area.  Sow the seed right after power raking.  If you have an all bluegrass lawn, it would be wise to match that type of grass, rather than use the fescue and rye mixture.

In recent years, it has been determined that power raking or aerating the lawn cuts and destroys quite a few of the insects, and often eliminates the need for spraying.

If additional information on the European Crane Fly is needed, consult your master gardener, certified nurseryman, or licensed pesticide dealer.


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