Tuesday, March 15, 2011

The Crane Fly Comes A-Callin' Now

Our mild temperatures lately have made for pleasant afternoons and evenings for backyard barbecues and garden chores...when it's not raining, of course. Another creature that is enjoying the evening temperatures in the 50's: the European crane fly, currently appearing on a porch light, window screen or white wall surface near you. A common sight for after-work lawn mowers this time of year are the masses of these crane flies on lawn surfaces, disturbed by the evening mowing.

The adult crane fly has very long legs and looks like a large  mosquito with a body about one inch long. Some homeowners are alarmed when swarms of these large flies gather on the sides of homes, but the crane fly does not bite or sting nor does it do any damage to houses. 

Conversely, some backyard bug aficionados think the crane fly is a beneficial insect, hence it's common misnomer, the "skeeter-eater."

    "This critter does not eat mosquitoes," says California Food and Agriculture entomologist Baldo Villegas. "And it is not a good bug. The larval stage of this insect is eating the roots of your lawn."

    Those crane flies you see in the evening are busy during the day, too. The females mate and lay their eggs in grass within 24 hours of emerging. 

These eggs develop into a worm-like larvae known as "leatherjackets", which are feeding on lawn roots from now until mid-May.

If you have brown spots in your lawn, here's how to determine if it's due to crane fly larvae, according to Washington State University, :

Dig down about three inches in your lawn, in a 6" x 6" square. Lift that block of lawn, and start crumbling it apart. If you have crane fly larvae (aka, "leatherjackets"), those one-inch long root munchers will be very apparent. Count the number of leatherjackets in that block of lawn soil, multiply that number by four, and that's the approximate number of leatherjackets you have per square foot. Repeat this test wherever you see the lawn turning brown. If that square foot total is less than 50, WSU advises against taking chemical action. If it is more than 50, consider replacing your turf with other landscaping.

Another possible culprit are white grubs, also known as masked chafers.These critters are about three-quarters of an inch long, and are usually c-shaped. Also, they tend to do their damage in late summer/early fall, not in late winter/early spring. Skunks enjoy digging these guys up out of your lawn on a moonlit night.

    There are chemical controls for the crane fly larvae (the leatherjackets), the most common being products that contain carbaryl as the active ingredient. However, because of the toxicity of carbaryl to bees, consider other alternatives first before spraying or putting down granules.

    "Keep your lawn well-fed throughout the year so it can tolerate a little bit of damage," says the Scott's Company Ashton Ritchie, who heads up their Lawns Division and is the author of the book, Scotts Lawns: Your Guide to a Beautiful Yard. "Follow a fertilization schedule that includes applications as per the package's instructions. Combine that with deep watering twice a week along with positioning your mower blade at a high setting (for cool season lawns) and your lawn will develop a deep, vigorous root system."

And a healthy lawn can stave off crane fly damage long enough for the garden good guys to move in. Predators such as birds can decimate a crane fly problem quickly. So, planting bird-friendly shrubs in the area can help you establish a permanent "air force base" for these welcome diners.

Many gardeners confuse crane flies with mosquitoes. Mosquitoes are about half the length of the one-inch crane fly, and tend to move as if on a serious mission, buzzing the whole time (crane flies are silent). And you should control those blood-sucking mosquitoes now. 

Here are some tips for mosquito control from the Yolo-Sacramento Mosquito and Vector Control District:



  1. Reduce standing water? Up here in the foothills I'm thinking of building an ark. My whole yard is standing water! Seriously Fred, do you have any suggestions to keep plants from drowning? I know prevention is the key but I've got standing water this year in places it's never been before.

  2. I noticed several of the white grubs mentioned here in my compost bin last year around this time. Are they harmful to compost? I imagine I wouldn't want to transplant them to my garden since they are root eaters. What type of management do you suggest for organic compost bins?

  3. hey Christine, I have heard you can spray beneficial nematodes with a pump or hand held sprayer to kil the grubs. I too had them in my compost pile, which I was told was because of too much water. I have aso been told they are good for decomposition and to let them ive in the compost...for ever answer there is always an oppisite one it seems :)

  4. oops nooo. My neighbour gave me some pile and I noticed several of the c shaped white grubs I mixed them into my yard... is it bad? I saw several of them and I was told they wouldn't harm anything by the neighbour...

    1. Yes these grubs will damage lawns and crops causing the sane brown spots as the leather jackets. The c-shaped grubs are said to be the larvae of the Japanese beetle, so if you find a way to keep those guys away it would help prevent them:) but I've personally used the beneficial nematodes and it seems to work well if you store them correctly and use them only when the directions say is an ideal time:)