Let's separate crane-fly facts from fiction
This is one of an occasional series of articles presented by the Green Gardening Program team.
Crane flies get a lot of attention this time of year, in part because they emerge in late August and early September.
With them comes an increased use of pesticides by people who hope to get rid of these large bugs and prevent lawn damage. The outcome: increased dangers to birds, water quality, fish life and other beneficial insects.
That's why Washington State University, the Washington State Department of Agriculture and the water-quality section of the Environmental Protection Agency got together this summer to form a crane-fly study group. Here's some myths they would like to share.
• Myth No. 1: Pesticides are the best way to deal with crane flies. The two most commonly recommended organophosphate insecticides for crane flies have been withdrawn from distribution by the EPA because of environmental toxicity.
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The EPA will prohibit Diazinon for all indoor use as of next year. It can't be used for home gardens beginning in 2003.
Besides, pesticides aren't that effective. New crane flies can hatch daily and often irregularly. The adults are scattered through a landscape and can't be reached with pesticides.
Spraying the whole area contaminates play areas, air, water and kills too many nontarget species. And new adults can fly in after you spray.
• Myth No. 2: Pesticides aren't that harmful. A 1999 study by the U.S. Geological Survey found nearly two dozen pesticides in King County streams, with concentrations of five pesticides exceeding federal limits set to protect aquatic life.
Diazinon was found in all 12 streams studied.
When these chemicals occur in measurable quantities in water, they imply overapplication or misapplication.
• Myth No. 3: All crane flies are bad and crane flies are all bad. Not so, they're necessary food for many creatures such as birds, fish, other insects like yellowjackets. Plus, some species recycle and decompose forest waste when the larvae feed on dead organic matter and wood. "Think of crane flies as bird food that won't attract rats," says Sharon Collman, entomologist for the EPA.
• Myth No. 4: Crane flies are all alike. The two pest species, called European crane fly (Tipula paludosa) and common crane fly (Tipula oleraceae) have dozens of relatives that are great fish food and also recyclers.
It's possible, with a little close observation, to tell the difference between the European crane fly (potential pest) and the "good guys." The "good guy" species have distinct patterns on their wings, the lawn pests do not. Wings of the European crane fly are smoky brown or tan with a dark area at the front wing edge. No patterns. For more tips on how to tell the difference, logon to the Web site www.whatcom.wsu.edu/cranefly.
• Myth No. 5: Crane flies around the yard must be laying eggs that will damage the lawn. Not necessarily. They may be just wandering around before dying or being eaten. Adults emerge from the ground at dusk after finishing pupating underground. They have no mission other than mating, and mating can last four hours.
The females then choose a soft, well-watered lawn, lay eggs immediately (most are laid by morning). If your lawn is dry and dormant, she may go elsewhere. (The European crane fly likes moist spots; the common crane fly will lay eggs in drier soil.) Eggs will hatch into larvae that live, feed and grow underground, often not doing much damage until spring.
• Myth No. 6: A sick lawn must indicate crane-fly damage. In late summer, lawns can look pitiful without any help from crane flies. Often, it's a result of compaction, lack of nutrients, thatch buildup or even lack of water.
To check for crane-fly larvae, look for bare or dying spots in the lawn with holes. In late winter or early spring, the larvae may even be out of the ground on the top of the soil or sod. Birds may be feeding in flocks. If you see these signs in late winter, dig up a square foot of lawn and count the larvae.
Healthy turf can withstand dozens of larvae, more than 40 per square foot. Gwen Stahnke, WSU turf agronomist says, "I've seen healthy turf on our deep Puyallup soils withstand as many as 80 crane flies per square foot."
Good soils allow lawns to survive crane-fly attacks because the roots grow deep and regenerate the grass effectively.
So what can you do?
Keep the lawn healthy, well-fertilized (recycling the grass clippings) and install the lawn over a good base of 6 to 8 inches of soil.
In addition to birds, there are some biological controls being tested.
Beneficial nematodes, applied in spring, provide a nontoxic biological control for affected lawns, eliminating about 40 percent of the larvae so that the lawn can recover better.
Before using them be sure to check the level of crane-fly problems.
Green Gardening Program
Experienced gardeners in the Green Gardening Program offer, for free, three slideshow presentations on site, whether it's in an employee lunchroom or at a neighborhood gathering.
They cover plant choice, pest control, lawn care, gardening to protect salmon and other topics. They also answer questions about water quality and reducing the use of pesticides.
Speakers are available days or evenings. Programs can last from about a half-hour to more than an hour. To schedule a presentation or to learn more, call 206-547-7561.
The Green Gardening Program is sponsored by Seattle Public Utilities and funded by the Local Hazardous Waste Management Program in King County.
Mary Robson is area horticulture agent for Washington State University/King County Cooperative Extension. She also is a primary member of the Green Gardening team, dedicated to educate the public on pesticide reduction.