How To Deal With Chafer grub in Your Irish Garden
What is Chafer grub?
Chafer grubs are the larvae of chafer beetles, living in the soil where they feed on grass roots and other plant roots. The garden chafer and Welsh chafer are the most common species causing lawn damage in Ireland. Chafer grubs are plump, creamy-white C-shaped larvae with brown heads and three pairs of legs near the front of the body. They are larger than vine weevil larvae, reaching 15-20mm at maturity. Adult chafer beetles emerge from the soil in early summer, flying at dusk to mate and lay eggs back in lawns and grassed areas. The grubs feed underground from late summer through the following spring, causing patches of yellowing, dying turf that can be peeled back to reveal the grubs underneath.
Damage Caused by Chafer grub
Chafer grubs cause yellow and brown patches in lawns where the grass roots have been eaten away. Affected turf feels spongy underfoot and can be peeled back like a carpet to reveal the grubs feeding on the root zone. Secondary damage is often caused by birds, particularly rooks, crows, magpies and starlings, which tear up the lawn to feed on the grubs. Badgers and foxes also dig up lawns to reach chafer grubs, causing additional severe damage. Chafer grubs can also damage the roots of young plants in borders and vegetable beds.
How to Prevent Chafer grub
Maintain a healthy, vigorous lawn that can tolerate some root damage without showing symptoms. Water lawns during dry spells in late summer when chafer grubs are actively feeding near the surface. Avoid leaving outdoor lights on during June and July evenings, as adult chafer beetles are attracted to lights and will lay eggs nearby. Encourage natural predators — birds, hedgehogs, frogs and ground beetles all feed on chafer grubs.
How to Treat Chafer grub
Apply nematode biological controls (Heterorhabditis bacteriophora) as a lawn drench in late summer (August-September) when the grubs are young and near the soil surface. The soil temperature must be above 12°C for the nematodes to be effective. Water the lawn thoroughly before and after application and keep it moist for two weeks. For severe infestations where turf has been destroyed, reseed or returf affected areas in autumn after treating with nematodes. There are no chemical controls available to amateur gardeners for chafer grubs.
Chafer grub in Ireland
Chafer grubs are an increasingly common lawn pest across Ireland, with reports of damage rising in recent years. The garden chafer is found throughout the country, while the Welsh chafer is particularly common in western counties. Ireland's mild, moist climate provides ideal conditions for chafer grub development. The damage is often most visible in autumn and spring when grubs are largest and most actively feeding. Secondary damage from birds, particularly rooks and crows tearing up lawns, is a common complaint from Irish gardeners. Coastal and rural gardens near grassland are most vulnerable.
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