The European crane fly earned a bad reputation for destroying lawns after it came across the border from Canada in the mid-1960s.
The larvae of the insect sometimes called leatherjackets live in the soil and feed on the roots of grass during fall and winter. From late August to mid-September, the adult crane flies emerge, mate and lay eggs.
The adult crane fly’s freakishly big legs and wings don’t help its reputation. Think mosquito on steroids. The adult doesn’t bite, eat, sting, suck blood or carry away small children. It’s the larvae that damage the grass. That doesn’t stop people from freaking out when the gangly flies emerge in late summer.
When the leatherjackets were at their worst a few decades ago, they damaged about one in 10 lawns, said Sharon Collman, an entomologist and Snohomish County extension agent.
“It hit the media and all people could see was a defoliated lawn and thousands of little wriggling worms,” she said.
She remembers newscasters interviewing distraught homeowners with stripped lawns.
In 1981, the Journal-American newspaper in Bellevue published a front-page story about European crane fly larvae with the headline “Attack of the Lawn Killers” dripping in blood.
“They came from Canada with little warning!” one headline screamed. Another choice front-page excerpt: “It couldn’t happen to me,” said a Redmond homeowner. “But it did!”
A week after that article ran, county retailers were sold out of diazinon, a chemical that kills crane flies, Collman said. The public got the message that crane flies needed to be eradicated.
Recent research suggests that these insects aren’t the lawn pests they once were.
Master gardeners surveying lawns in the Lake Whatcom area in 2001 found 95 percent of lawns had no or very few crane flies. The other 5 percent had 20 to 25 larvae per square foot, a level that doesn’t require any treatment.
In the following years, researchers continued to test Lake Whatcom area lawns and found fewer and fewer larvae. In five years more than 300 lawns have been tested and not a single one has had populations large enough to require an insecticide.
Their numbers went down in part because natural predators such as starlings, crows and robins have discovered leatherjackets are a good food source, Collman said. She has even observed yellow jackets cruising around turf for crane fly adults.
Even if a few are present, experts now know a lawn can support 25 to 40 per square foot with no damage, depending on the health of the lawn.
Yet, the pesticide-buying habits of local homeowners suggest we’re still applying insecticides like it’s 1981.
Western Washington homeowners spend an estimated $12.8 million a year on pesticides to combat the European Crane Fly, according to the extension agency.
The result? In 1999 the state Department of Ecology found traces of three insecticides used to treat crane flies in the watershed of Lake Whatcom, a drinking-water source for 85,000 people.
The levels found aren’t considered harmful for humans, but it’s a warning sign.
Reporter Debra Smith is a master gardener. You can reach her at 425-339-3197 or dsmith@heraldnet.com.
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