Slug

• Irregular holes in leaves, often starting from the leaf edge — damage is at its worst on seedlings, lettuce, hostas, and strawberries
• Shiny, dried silver slime trails on leaves, soil surface, or pots the morning after feeding
• Seedlings clipped off at the soil line overnight, with no visible caterpillar or obvious insect
• Damage confined to lower leaves and ground-level fruit — slugs rarely climb more than a few feet
• Strawberries, ripe tomatoes dropped to the ground, and lettuce heads with hollowed-out centers
• Slugs visible when you lift boards, pots, or dense mulch in the morning — they shelter by day

Most garden slugs are active at night and during overcast, wet days. They are not insects — slugs are mollusks — but cause damage patterns similar to caterpillars. Eggs are laid in clusters under debris and in the top inch of soil; a single slug can lay 200–400 eggs per year. Populations peak in cool, moist conditions — spring and fall in most climates, or year-round in mild coastal gardens. Hot, dry summers suppress slug activity significantly. Deroceras reticulatum (gray field slug) is the most common garden species in North America, but several others including Arion and Limax species may be present depending on region.

1. 01Reduce hiding spots: pull mulch away from plant stems, remove boards and debris, and avoid overhead watering in the evening
2. 02Water in the morning rather than evening so soil surface dries before slugs become active at night
3. 03Set board traps: lay a plank near damaged plants; slugs shelter underneath and can be collected and dropped in soapy water each morning
4. 04Apply iron phosphate bait (sold as Sluggo and similar products) around vulnerable plants — it is OMRI-listed for organic use, low toxicity to mammals and birds, and remains effective after rain
5. 05Diatomaceous earth around plant bases provides short-term deterrence in dry conditions but loses effectiveness once wet
6. 06Copper tape around raised beds or pot rims can deter crossing, though effectiveness varies and tape must form a complete seal

If seedling losses are severe and you cannot confirm slugs as the cause — some seedling damage may be from cutworms or earwigs — your local extension office can help distinguish based on damage pattern and time of year.

• Slugs in the Home Garden— UC ANR Integrated Pest Management
• Slug and Snail Management— Oregon State University Extension