Management of European Chafer Double Shot
By Mario Lanthier
“No insect causes more damage in Michigan lawns than European chafer” said Dr. David Smitley. “The damage is often misdiagnosed - European chafer adults fly at night and home owners think the grubs in their lawns are Japanese beetles.”
The presenter is a turf entomology specialist and is known as “the man who wrote the chapter” on European chafer. He was speaking at the Michigan Turfgrass Conference held this past January in East Lansing (see the website www.michiganturfgrass.org).
European chafer has been found for many years in Michigan. The cool weather pest arrived from Europe and spread rapidly before natural enemies could establish. The worst damage is in the fall when small animals such as raccoons destroy the lawn while feeding on the grubs found in the root zone.
Dr. Smitley suggested the following management tactics for European chafer.
1) Water during dry periods. This is especially important in September and October when grubs are most active. “This insect is a problem of drier sites. We rarely see any grub damage in lawns with a good irrigation system” added Dr. Smitley.
2) Raise the mowing height. Higher mowing means more roots, thus less stress from grub feeding. “Lawns with a large root system are more tolerant because a very heavy infestation of grubs will never consume more than 50% of the roots” said the presenter. “If you combine mowing high with modest applications of fertilizer and watering during dry periods, you may not need to use any insecticide on your lawn – or any herbicide to control weeds, for that matter”.
3) Where pesticide can be used, spray in June or July in areas with damage the previous year, and follow with ½ inch of irrigation to wash into the roots.
Said Dr. Smitley: “The early spray is targeting young grubs before there is visible damage. Over 20 years of field trials, there is 100% control when spraying at the proper time followed by irrigation. An application without irrigation will give about 90% control”.
Products registered in Canada include Acelepryn, Arena, Merit and Quali-Pro.
The presenter is a professor at Michigan State University. For more on European chafer (Rhizotrogus majalis), see the excellent website msuturfinsects.net.
“Create a resilient foundation” was the theme of a talk by Dr. Michael Brownbridge at the Landscape Ontario Congress, held in Toronto in early January.
“For European chafer, nematode applications work, but the trials show the efficacy is 40 to 60%, consistently year after year” he said. “Is this enough? It may be if we integrate multiple strategies that work well together and provide the desired level of control” he added.
First, promote turf health with practices such as irrigation, mowing, aeration, fertilization and overseeding. Next, examine the grass types. “This is becoming more critical” he added “especially for drought tolerance and reduced maintenance”. In trials at the Vineland Research Centre in Ontario, lawns seeded to perennial ryegrass and fescue had the fastest establishment and less than 5% weed cover. “Seed with grass blends” he concluded, for example mix Kentucky bluegrass with endophyte-enriched ryegrass or fescue.
The parasitic nematode Heterorhabditis bacteriophora is currently used in commercial programs in Ontario for control of European chafer. The provincial legislation is restricting the use of pesticides on residential lawns. The nematode application is made after the first rain of August (after egg hatch of the insect) using 2 gallons of spray solution per 1000 ft2. “Moisture is important, especially in loam or clay soils - too dry or too wet, these nematodes will not work as well“” said Richard Reed of Lawn Life Natural Products. “Steinernema scarabaei is a much better product to control European chafer with efficacy up to 95%” he added, “but it is not yet commercially available”.