Chafer beetles: how to manage an infestation
What is a chafer beetle?
The European chafer beetle (Rhizotrogus majalis) is a new turf pest in the Lower Mainland that was recently identified in West Vancouver. It has been a serious pest in Eastern North America for some time and was first identified in New Westminster in 2001. It has since spread to many Metro Vancouver municipalities, causing considerable damage to lawns, boulevards and medians.
Damage to lawns and boulevards
Chafer beetle populations grow quickly, damaging turf on lawns, boulevards, grass sports fields and parks. The grubs feed on the roots of grass lawns. In drier weather, the damage appears as brown patches in the lawn. Birds and animals (especially skunks and crows) cause further damage by digging for the grubs. Damage by animals is most severe in the fall and spring when the grubs are rapidly increasing in size and feeding near the surface. Chafer beetles have a one-year life cycle.
The only way to confirm the chafer beetle’s presence is through a simple test conducted between January and March. By digging up several test sections in both affected and unaffected areas, you can monitor for grubs while they are near the surface.
Cut five sample sections that measure 30 cm x 30 cm (1 square foot). The grubs, measuring 2-2.5 cm, are soft, white and C-shaped with tan-coloured heads and six legs. If you count five or more grubs per square foot, control measures may be warranted.
Maintaining a healthy lawn is the first step in protecting against grubs. Healthy lawns have a more extensive root system and can tolerate more grub feeding. More tips for a healthy lawn:
- for healthiest roots, a lawn only needs to be watered one hour per week, or less if it rains.
- don't cut your grass too short. Beetles prefer laying eggs on closely cropped lawns, so raise your mowing height to 6 to 9cm (2.5 to 3 inches). The higher blades also help protect the soil surface from water loss and encourage deeper root growth.
- consider using alternative ground covers such as woody ornamentals on selected areas of your lawn.
- compact your lawn before eggs hatch in June to early August, as it causes the newly hatched grubs to have difficulty moving, resulting in some mortality
Some residents have had some success preventing chafer infestation with the use of Remay cloth, plastic sheeting, or landscape fabric to cover their lawns before dusk in June and July when the adult beetles are most active. A cover may prevent mated females from laying eggs in your turf and repeating the cycle. (Note that some covers may need removal each morning).
The application of nematodes has proven to be the most effective approach to managing the chafer. Nematodes are microscopic roundworms that live in wet soil and feed on insect larvae.
Note: Nematodes are most effective when applied the third or fourth week of July when the chafer larvae are small and most vulnerable to nematode infection. During treatment, the application area should be well irrigated early in the day so that there is no dry soil in the root zone.
Special lawn sprinkling permit (for nematode application)
Lawn sprinkling regulations are in effect from May 1 to October 15 annually. Lawn sprinkling permits may be required for extra lawn irrigation during nematode application, which is most effective in the third and fourth week of July. Permit details:
- the permit is free
- expires three weeks from the date permit is issued
- lawn sprinkling permits are approved for nematode application or newly seeded/turfed lawns only
- receipt for the purchase of nematodes must be presented to Engineering as confirmation
- the permit must be displayed during sprinkling outside of designated watering hours