How Do I Stop Slugs Eating My Radishes?

Slugs cause two types of damage to radish: seedling damage, where emerging radish shoots are eaten at or just below the soil surface leaving a clean snapped stem or simply disappearing overnight; and root damage, where slugs tunnel into developing roots, leaving irregular channels and holes that make the radish inedible. Both types of damage are most serious in cool, wet conditions — the exact conditions that spring and autumn radishes prefer — making slug management a perennial challenge for radish growers.

Why radish is particularly vulnerable

Radish matures in three to four weeks — a very short window. This means there is not time for the plant to recover from slug damage in the way a longer-season crop can. A seedling eaten by slugs simply needs to be resown; a root tunnelled by slugs at week two or three is a write-off. The speed of the crop means each sowing needs protection from day one.

Ferric phosphate pellets

Ferric phosphate slug pellets (sold as Ferroxx, Sluggo or similar) are the most effective and safest organic slug control available. The active ingredient breaks down to iron and phosphate — both natural soil components — making them safe for wildlife, pets and soil organisms. Apply sparingly at the label rate around the bed immediately after sowing. Reapply after heavy rain. Do not apply so heavily that pellets are clearly visible — one or two per 30 cm squared is sufficient.

Nematodes

Phasmarhabditis hermaphrodita nematodes, watered into moist soil at soil temperatures above 5°C, infect and kill slugs in the soil. They are highly effective against the soil-dwelling slug species that damage roots (particularly Arion subfuscus and Deroceras reticulatum) and last approximately six weeks. Apply two weeks before sowing and again after sowing for maximum protection. They are particularly valuable for protecting roots from underground slug tunnelling.

Physical barriers and cultural practices

Copper tape around raised beds deters slugs on the outside. Coarse grit or sharp sand on the soil surface creates an unpleasant surface for slugs to cross. Removing hiding places — debris, boards, stones — near the growing area reduces the resident population significantly. Evening patrols with a torch and hand-picking are time-consuming but effective for visible surface slugs.