How to get rid of slugs in the garden

Slugs can wipe out a row of lettuce or a flat of seedlings in one night. They love damp weather, cool nights, and shady, sheltered beds. A few simple habits cut their numbers fast.

Signs of slugs

• Ragged holes with smooth edges, often in the middle of leaves
• Seedlings chewed down to bare stems
• Shiny, silvery slime trails on leaves, soil, and paths
• Damage that shows up overnight, with no pest in sight during the day

Slugs feed at night and on cloudy, wet days. During the day, they hide under boards, rocks, mulch, pots, and thick leaves.

Their favorite plants include hostas, lettuce, strawberries, cabbage, beans, basil, dahlias, and almost any seedling.

1. Hand-pick slugs at night

Hand-picking takes a few evenings, but it works. Go out an hour or two after dark with a flashlight. Rainy nights and evenings after watering are best. Pick slugs off your plants and drop them into a jar of soapy water. Wear gloves, since slug slime is hard to wash off.

Do this a few nights in a row, and you will see fewer slugs each time.

2. Set traps

Beer traps

Slugs are drawn to the yeast smell of beer.

1. Sink a shallow container, like a yogurt tub, into the soil.
2. Leave the rim about 1 inch (2.5 cm) above the soil so ground beetles do not fall in. Ground beetles eat slugs.
3. Fill it halfway with cheap beer.
4. Empty and refill it every 2 to 3 days, and after rain.

No beer? Mix warm water, a spoonful of sugar, and a pinch of dry yeast. It gives off the same yeasty smell.

Board traps

Lay a board, a flat stone, or a grapefruit half (cut side down) on the soil near damaged plants. Slugs crawl under it to hide. Lift it each morning and scrape the slugs into soapy water.

3. Use iron phosphate bait

Iron phosphate slug baits, like Sluggo, carry a lower risk to pets and wildlife than older baits. Slugs eat the bait, stop feeding, and die within a few days. Bait that slugs do not eat breaks down in the soil.

Scatter it thin around your plants, as the label directs. Do not leave it in piles. Put it out in the evening, after rain or watering, when slugs are active. Keep all baits away from pets, since a dog can still get sick from eating a large amount.

Avoid metaldehyde baits. Metaldehyde is poisonous to dogs, cats, and wildlife. Read the label before you buy any slug bait.

4. Water in the morning

Slugs need moisture to move. Water early in the day so the soil surface dries by evening. Drip lines and soaker hoses keep the surface drier than sprinklers do.

5. Remove hiding spots

• Pull weeds and clear away boards, empty pots, and debris near your beds.
• Keep the grass trimmed along bed edges.
• Pull thick mulch back from seedlings in spring. Add it again once plants are bigger and the weather warms.
• Space plants so air can move between them.

6. Welcome slug predators

Ground beetles, toads, frogs, garter snakes, and many birds eat slugs. A small pond, a rock pile, or a quiet corner gives them a home. Avoid broad-spectrum insecticides, which kill ground beetles too. If you keep chickens or ducks, they will eat slugs as well.

7. Protect your seedlings

Seedlings are most at risk. A slug can eat a young plant to the ground in one night. Start seeds indoors and set out bigger, sturdier transplants. A bigger plant can lose a few leaves and keep growing.

Containers help too. In a Royal Horticultural Society trial, lettuces grown in pots had much less slug damage than lettuces grown in the ground.

8. Clean up slug eggs in fall

Slugs lay clusters of small, round, clear or white eggs in damp soil and under debris. In fall, check under boards, pots, and leaf piles. Scrape any egg clusters into the trash. Fewer eggs now means fewer slugs next spring.

What does not work

Copper tape, crushed eggshells, sharp grit, pine bark, and wool pellets are popular slug barriers. The Royal Horticultural Society tested all five around lettuce plants. None of them reduced slug damage compared with lettuces that had no barrier. Slugs glide over rough surfaces on a thick layer of slime.

Salt kills slugs, but it also damages the soil and your plants. Skip it.

Diatomaceous earth only works when it is dry. It stops working once it gets wet, which is when slugs come out.

Plants that need the most protection

Some plants are slug magnets. Give these extra attention in spring:

• Hostas
• Strawberries
• Lettuce
• Spinach
• Basil

For other common pests, see my guide to garden pests.