CORVALLIS, Ore. — As gardeners wind down for the season, slugs are just getting started. In fall, these slimy pests emerge to lay eggs for the coming year, making it a critical time for control.
In fall, when temperatures cool and rains return, slugs lay eggs in clusters that overwinter and hatch quickly in spring.
“What slugs want is a place that’s warm and moist,” said Claudia Groth, Oregon State University Extension Service Master Gardener. “That’s why spring and fall are when they’re most active. They’ll be coming out soon to lay eggs.”
Slugs are less active in the extremes of summer and winter. But in fall, when temperatures cool and rains return, they lay eggs in clusters that overwinter and hatch quickly in spring.
“In fall, you’re trying to kill them off before they lay eggs,” Groth said. “In spring, when your plants are poking their heads up, you need to protect them, because once the leaves are nipped, the damage is there all summer.”
Favorite foods include lettuce, broccoli, beans, hostas, strawberries, primroses and daffodil flowers. Plants that slugs usually avoid include ferns, sedums, ornamental grasses, bleeding heart (Dicentra), coral bells (Heuchera), hellebores and most herbs. Woody plants are rarely affected.
First step: sanitation
Because slugs hide during the day, gardeners often find them under mulch, boards, pots, bricks or dense plantings.
“The first thing to do when starting a control program is to clean up the garden,” Groth said. “Don’t leave things all over the yard. They can even hide under garden gloves.”
Tips:
- Raise pots on bricks or pot feet.
- Pull mulch away from vulnerable plants.
- Remove weeds and debris.
- Tidy under porches, decks and other structures.
Other control strategies
Once the garden is cleaned, Groth recommends combining several methods:
- Water in the morning. Evening irrigation creates ideal conditions for nighttime feeding.
- Beer traps. Sink shallow containers into the soil and fill with beer. Empty and refill daily.
- Copper barriers. Wrap a 3–4 inch band of copper around raised beds or pots.
- Predators. Encourage frogs, ground beetles and snakes. Ducks will also eat slugs, though local restrictions may apply.
- Handpicking. Go out at night with a flashlight and drop slugs in soapy water.
- Trap boards. Place boards in slug-prone spots. To increase effectiveness, bait with chopped lettuce and brewer’s yeast. Check in the morning and dispose of slugs.
- Avoid salt. It damages soil and plants.
Baits: read labels carefully
Two main types of slug baits are available:
- Metaldehyde-based baits: Synthetic and toxic to humans, pets and wildlife if ingested in large amounts.
- Iron phosphate-based baits: Approved for use in organic gardens, considered low in toxicity but still risky to pets if consumed in quantity.
When using baits:
- Scatter lightly rather than making piles or bands.
- Follow label directions closely. Using more than recommended does not improve results.
For additional details, consult Extension’s publication How to Control Slugs in Your Garden.
Previously titled Control slugs now as they lay eggs to hatch in spring
