Wireworms: how to recognise and treat it

Pest

Symptoms

Narrow tunnels straight through potatoes and other root crops, entered by round holes about 3 mm across, as if made by a nail; slugs instead leave larger cavities.
Seeds fail to come up and rows are patchy; seedlings have small holes in the stems and may die.
Plants are stunted and wilt, especially when small or short of water.
Thin, yellowish-brown larvae up to 25 mm long with three pairs of short legs behind the head in the soil.
Worst in beds newly dug from lawn or grassland.

Bury nearly full-grown carrots across the bed; every 2–3 days pull them up, destroy the wireworms and put them back.
Pick out and destroy wireworms whenever you dig.
Water the nematode Heterorhabditis bacteriophora into moist soil when it is 12–20 °C (April–September); repeat if needed.

Insecticides are rarely warranted in a garden. Where wireworms have caused damage before, a soil insecticide registered for the crop can only be worked into the soil before planting — it does not work once damage is seen; follow the label.

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

Numbers fall within about two years of regular cultivation, so in a bed newly made from grass avoid potatoes and root crops at first.
Dig the soil to expose the larvae to birds, and encourage birds, hedgehogs and ground beetles.
Keep weeds and grass down in and around the vegetable beds — click beetles lay their eggs in grassy, weedy ground.
Sow later into warm soil so seedlings establish quickly, and improve drainage in wet spots.
Rotate crops and avoid the most susceptible vegetables where wireworms have been a problem.

Figures checked against these sources.