slugs & snails

Symptoms

Irregular holes with smooth (not jagged) edges eaten from leaves, flowers and soft stems, often starting at the margins; whole seedlings can vanish overnight; tender hostas, lettuces and bedding are stripped; the tell-tale sign is a silvery dried slime trail on leaves, soil and pots. Damage is worst at night and in mild, wet weather.

Plants affected

• dahlia
• pansy
• begonia
• lettuce
• lupin
• primrose
• French marigold
• delphinium (larkspur)
• foxglove
• bearded iris
• sweet pea
• nasturtium

Easily confused with

• Pythium damping-off + root rot (multi-host)

  How to tell them apart: Slugs/snails (Gastropoda) sever sweet pea seedlings with a clean, ragged mechanical cut at or just above the soil line, leaving the toppled stem firm and dry; look for irregular holes rasped from leaf edges, missing cotyledons, and tell-tale silvery dried slime trails on the soil and stems, with worst damage after damp nights. Pythium ultimum damping-off instead produces a soft, water-soaked, brown-to-black pinched and shrivelled lesion girdling the stem base, so the seedling wilts and keels over while still attached by collapsed mushy tissue; there is no clean cut, no slime, and often a fluffy white mould and rotted roots in cold, wet, overwatered compost. Key tell: a firm severed stump with slime points to slugs, a slimy-but-fungal rotten thread of tissue points to Pythium.

• Hosta virus X (HVX)

  How to tell them apart: Slug/snail (Gastropoda) feeding leaves clean-edged, irregular HOLES rasped right through the blade and chewed leaf margins, very often with a tell-tale silvery, dried slime trail across the leaf or on the soil; damage is worst on tender lower leaves, appears overnight, and the surrounding tissue keeps its normal green colour. Hosta virus X (HVX) instead shows a discoloration pattern that follows the VEINS: dark blue-green 'ink-bleed' bleeding along veins, green-and-yellow blotchy mottling, ringspots and puckering, and lumpy collapsed tissue that can later dry, necrose and TEAR — producing ragged holes that imitate chewing but with NO slime trail and always tied to the mottled/ink-bleed colour change. Rule of thumb: holes + slime + normal green = gastropods; vein ink-bleed + mottling + collapse = HVX. HVX is incurable, so any vein-following mottling means destroy the plant, not reach for slug pellets.

Common questions

How do I recognise slugs & snails on dahlia?

Irregular holes with smooth (not jagged) edges eaten from leaves, flowers and soft stems, often starting at the margins; whole seedlings can vanish overnight; tender hostas, lettuces and bedding are stripped; the tell-tale sign is a silvery dried slime trail on leaves, soil and pots. Damage is worst at night and in mild, wet weather.

Do I have to report slugs & snails?

No. slugs & snails is not a notifiable organism, so there is nothing to report to an authority. Treat it as a normal garden problem.

How is slugs & snails treated?

Mainly with biological and cultural measures — removing affected material, changing the conditions that favour it, and treating with agents approved in your country. The exact steps and their timing depend on the plant, the season and where you live: Dr. Phyto works them out in a free diagnosis.