Chafer grubs: how to recognise and treat it

Pest

Symptoms

Fat, C-shaped, creamy-white grubs with a brown head and three pairs of legs at the head end, in the soil around roots; up to 18–30 mm long depending on the species.
Plants with eaten roots turn yellow, wilt or die; often nothing shows above ground until harvest.
Potatoes, beetroot and other root crops have large, shallow, round holes.
In lawns, yellowish patches and turf torn up by crows, magpies, badgers or foxes digging for the grubs, mostly from autumn to spring.

Collect and destroy the grubs as you dig and prepare the soil — they move back into the soil if left.
Water in the nematode Heterorhabditis bacteriophora when the soil is moist and 12–20 °C; as a preventive, apply in July–September, following the supplier's instructions.
Birds and other animals feed on the grubs; turning the soil exposes them.

Insecticides against full-grown grubs in the garden are impractical and ineffective; rely on hand collection, cultivation and nematodes.

Reference information, not a guarantee. Read and follow the label of any product: dose, safety and the days to wait before harvest.

Dig or plough in late summer or early autumn to kill grubs and expose them to birds.
Avoid planting vegetables where there was grass, corn, potatoes or an old strawberry bed the year before — grubs are worst in freshly dug-up lawn.
Keep the garden weed-free (beetles prefer to lay eggs in well-covered soil) and well drained.
Keep the vegetable plot away from plants the adult beetles favour, such as oaks, grapes and roses.

Figures checked against these sources.