European Chafer – A New Pest in The Lower Mainland
The European Chafer, Rhizotrogus majalis, is a serious pest of turf in eastern North America. In 2001 it was found in New Westminster, British Columbia, in lawns and boulevards. It is probable this pest has been in B.C. for a few years, and has now spread beyond New Westminster. In fact, while doing a bit of gardening in our yard we had a rain of beetles falling on our heads.
Description
The adult beetle (Figure 1} is tan coloured and resembles a smallish June beetle. The larvae, or grubs (Figures 2,3}, have a C -shaped body and brown head. Mature chafer grubs are smaller than mature June beetle grubs. A microscope is required to confidently identify the grubs.
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Figure 1: Adult European Chafer. |
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Figure 2: Mature European Chafer grubs |
Biology
The European chafer completes its life cycle in one year. The adult chafer beetles swarm in conspicuous mating flights on warm evenings in late June and early July. The beetles fly to tall objects, usually trees or other vertical structures to mate. The adult females then locate nearby lawns to lay their eggs in. The females deposit up to 50 eggs each.
Eggs hatch in late July or early August and the larvae or grubs begin feeding on roots until the ground freezes. In colder climates, the larvae migrate down below the frost-line to overwinter.
From April to mid-May, the larvae migrate close to the soil surface and feed on turf roots. From mid-May to early June, the larvae stop feeding and pupate (undergo metamorphosis), and the adult beetles emerge two weeks later.
Damage
The grubs are the damaging stage. They feed on all types of grass and, if numerous and food is scarce, may move into vegetable plantings to feed on corn, potatoes and other crops. European chafer grubs prefer to feed on fibrous roots, and can damage ornamental and nursery plants by reducing their fibrous root system. Most of the damage is done by the the third (final} instar grubs in the fall and early spring, but damage can be masked by the abundant moisture at these times. Drier weather can quickly result in the appearance of brown, dying patches. Considerable damage to turf can occur in the fall and winter from animals, especially skunks, and birds digging up the grass to feed on the larger grubs (Figure 4).
The adult beetles feed at dusk on the leaves of deciduous trees but, even when numerous, seldom cause significant damage.
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Figure 3: European Chafer grubs in turf |
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Figure 4: Boulevard damage caused by skunks digging out grubs. |
Monitoring
In the Spring or Fall, turf that has been damaged by white grubs will lift away from the soil easily because the roots have been eaten and they no longer anchor the turf to the soil. Often, raccoons and skunks will pull back the turf in search of a meal of grubs. This secondary damage is usually more extensive than that caused by the grubs.
Turf that has been severely damaged by birds or other animals may also be brown, wilted or tufted in appearance. Grubs will often be visible when the turf is pulled back. Damage is most severe in the fall and the spring when the grubs are increasing in size rapidly and feeding near the surface.
To confirm the presence of European chafer grubs in your lawn this spring or fall, do the following:
- Use a garden shovel or spade to cut three sides of a 12-inch square.
- Grasp the open edges and peel back the turf like a carpet, towards the attached side.
- Look for the white, C-shaped grubs (larvae) or cocoons (pupae) in the soil, and just underneath the turf roots.
- Repeat Steps 1 to 3 in at least five different sections of lawn.
- If you count five or more white grubs per square foot, consider applying a (non-toxic) biological treatment in the summer.
- If you are unsure of what you have found, place a grub inside a jar or plastic bag, and take it down to your local specialty garden centre for identification.
Management
Healthy, vigorous, well-irrigated turf can withstand low levels of grub feeding.
Biological Treatment
A 2005 study commissioned by the Western Canada Turfgrass Association, the Canadian Nursery Landscape Association, and several local municipalities, revealed that biological treatments could be very effective at controlling the European chafer population, when used in combination with healthy lawn care practices.
According to the study, the most effective biological control measure was the nematode (or roundworm) Heterorhabditis bacteriophora – a natively occurring species that has been used successfully in BC to control other pests. The H. bacteriophora nematode is a “cruiser” species that actively seeks out white grubs (such as the European chafer), and quickly destroys them from the inside-out.
Treatments are most effective if done in late July, after the European chafer eggs have hatched and when the young grubs are most vulnerable to nematode attack.
Book your nematode treatment in the spring, by doing one of the following:
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Inquire at a specialty garden centre about ordering nematodes and applying them to your lawn in late July. “Nemasys G” is one of a few brand names to look for. Stratas may inquire about bulk purchase rates from wholesalers/distributors of these products; OR
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Find a lawn contractors in your area by searching in the phone directory under “Lawn Maintenance”. Receive one or more quotes for the application of H. bacteriophora nematodes to your lawn in July
What is the long term solution?
In order to prevent European chafer damage in the long-term, many residents are now considering the use of alternative ground covers – particularly on sites that are sunny and well-draining, and prone to yearly infestations.
Groundcovers can be selected to be aesthetically pleasing year-round and to require minimal maintenance. They may also be incorporated with foot paths to increase their aesthetic value. Mulch or paving stones can also be considered in high traffic areas.
Trifolium repens (Dutch White Clover) is one example of a low-growing plant that will form a green, durable ground cover that is easy to maintain. It also produces tiny white or pale pink flowers that may attract bees and other beneficial insects to your yard.
Some of the options of a turf yard. White clover mixed with grass and wildflowers.
Links
- Effective Control of White Grubs (Health Canada)
www.pmra-arla.gc.ca/english/consum/whitegrubs-e.html – [NEW WINDOW]
- Healthy Lawns (Health Canada)
www.healthylawns.ca – [NEW WINDOW]
- Organic Grub Control (Living Green)
www.livinggreen.info/library/organic_grub_control.cfm – [NEW WINDOW]
- Preventing Raccoon Problems (Ministry of Environment)
www.env.gov.bc.ca/epd/epdpa/ipmp/Brochures/racoons.htm - [NEW WINDOW]
- Wildlife in the City: Racoons (City of Toronto)
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