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European Crane Fly Control through IPM

December 7, 2009

December 5, 2009

Integrated Pest Management (IPM) is being adopted and actively sought by growing numbers of property managers. Professional pest managers must be competitive in commercial property work; and, the cost benefit of IPM, without chemicals, is being proven in commercial landscape management. It is in home pest management that unnecessary chemical control can readily occur. The following is directed principally to the homeowner and yard maintenance manager.

It has been many years since I used a chemical pesticide–diazinon/Dursban, both now banned for residential use- to “control” European Crane Fly (Tipula paludosa) on my own property. Professionally, I have seen a clear need for immediate use of a pesticide only twice in 25 years. Both situations were in new landscape where turf, seeded and sodded, was not established. Chemical control is rarely needed in established lawns, according to my research and own experience.

I live in South King County on Alderwood [Series] Soil (Alderwood rock potatoes), which is not conducive to lush lawns. My personal IPM strategy is to “watch and monitor” the soil for larvae. Ignore the adults, huge “mosquitoes having legs ” spanning 2-inches  in late summer. Adult flies are at their worst when fluttering around inside the house.

Watch, Monitor, and Wait

To monitor, I simply cut into turf in fall and spring to count larval populations. I cut at an angle in several locations, using a common spading shovel and peel back the flap of sod and soil. The sod flap falls back into place seamlessly. I  can find two to four larvae in a test cut, which is nowhere close to levels that may encourage calling in the chemical army. The Washington State University Research Station in Puyallup considers up to 4 larvae in a 3-inch diameter bulb planter safe. However, due to my mostly rocky soil, I can’t use a bulb planter in my lawn. Using a shovel, I would need to see ten or more larvae to become concerned. If I did, I would wait until the next spring to take another sampling: so far, I only count larvae.

Help Nature Manage Lawn Health
Over the years that I have been monitoring T. paludosa on my property, I observed two conditions that seem advantageous to their growth. The first is deep, loamy soil; good lawn soil is also good for crane flies. The control of crane fly was an accident: I was actually adjusting my watering regimen for optimum water conservation. I had modified their cultural conditions by watering only at the point of grass dehydration,  then applying 0.75 inch of water in a single cycle. The larval population in the previously wet test digs had declined to those in hard soil when I sampled during the following spring.  

The second condition appears to be related to natural enemies of the European Crane Fly. The only scientific evidence I have for this is that larval populations in the tests were highest the year following application of diazinon, which was over ten years ago. The population declined to current levels in the third year.

My prognosis for this decline may be influenced by a dread of using chemical control for pests, but I feel that diazinon only exacerbated infestation in a relatively stable environment.  Currently listed chemicals for control of crane fly are extremely toxic to many other animals.  With pets (dogs) causing more visible damage to my lawn than a pest, I am not inclined to expose pets and our indigenous and native friends to physical harm.

Keep the Lawn Healthy
My only active management strategy for crane fly is turf maintenance.  Crane fly monitoring is only incidental to the casual efforts I have with lawn management.  We joke about the cobbler’s children’s shoes, but I prefer to think he is thrifty; and so too is my lawn management. I’m an experimental gardener and don’t care to have the neighborhood show piece yard.  Watering is done only when the turf is showing signs of stress. Most people want to water more than needed when lawns start looking yellow.  The grass actually needs fertilizer.  Ideally, I try to fertilize at least four times during the growing season, usually more often with lighter applications, taking a break during our summer drought season, from near 4th of July  through late August.

I use ammonium sulfate at an N-P-K ratio of 20-0-0.  A 20-pound bag has 4 pounds of elemental nitrogen. Phosphorus and potassium (P-K) are not needed for lawns in the Puget Sound region. This fertilizer is the least costly, but is fast acting, so best for homeowners who can distribute it in small amounts with a handheld broadcast spreader, after every second mowing, not wasting excess to leaching.  4 to 6 pounds of nitrogen per 1000 square feet is plenty for one year. About every second year, I will spot treat weeds.

Healthy turf is the first line of defense in crane fly management. I think my thrifty strategy exemplifies a not-too-rigorous, but successful, management plan.

Learn More – Resources
There are several good online sources providing more information on European Crane Fly and management. The two cited below are very good:

  • Seattle Public Utilities’ Integrated Pest Management ProIPM Fact Sheets has a good PDF file, “Crane Fly-European,” written in 2006 and available as of December 2009. It details identification, life cycle, and management strategies, including current chemical controls. As noted, chemical treatment is rarely needed.
  • The second online source published by Washington State Extension is “EB0856, European Crane Fly: A Lawn and Pasture Pest”. The 1998 publication focuses on nonchemical management and is a good source of information for monitoring methods.
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