- Backyard and garden insects
- Slugs are present from spring to autumn, in cool, humid and shady areas.
- Slugs feed on the leaves of many plants (especially seedlings), ripe fruits and vegetables, and decaying plant matter.
- Extensive feeding can result in a weak or dead plant.
- There are several non-chemical steps to fighting slugs.
- Insecticidal baits are also available if needed.
how to identify slugs
Slugs can be described as shelled snails. They are a type of mollusc, related to clams and oysters.
- Slugs are slimy and soft-bodied with no legs.
- They are generally brown or gray in color.
- Its head contains two pairs of antennae. A larger pair above carries the eyes and a smaller pair below is used for smelling.
- They can vary in size from 1/4 inch to two inches or more.
Slugs produce slime and use it to move around. A dried slime trail indicates that slugs are active in your yard.
Slugs are usually active at night when it's cool and wet, although they can be seen during the day in cool, shady places. Hot and dry conditions are less favorable for them.
- Slugs typically overwinter as eggs in protected places, such as under plant debris, mulch, boards, or in the ground.
- The eggs hatch the following spring and early summer.
- If conditions are favorable, slugs can be active during summer and fall.
- Slugs have a slime coating to keep their skin from drying out.
Slugs feed on a variety of ornamental plants that grow in partial shade, as well as fruits and vegetables. Some plants that are likely to harm include morning glory (Campanula), delphinium (Larkspur), banana lily (hosta), lily (Hemerocallis),Dahlia, pulmonary (Pulmonary), strawberry, basil, beans, cabbage and lettuce.
Ground covers such as spotted dead nettle (Lamium maculatum) create a welcoming habitat for slugs by shading the soil and keeping it cool and moist.
Slugs generally don't bother plants grown in full sun.
- Slugs use file-shaped mouthparts (called a radula) to scrape and chew plant tissue.
- Due to their mouthparts, they create irregularly shaped holes in leaves, flowers and fruits.
- Low to moderate feeding can affect the appearance of the plants, but generally does not affect the health of the plants.
- Severe slug feeding can damage plants, especially seedlings.
- It can also reduce fruit and vegetable yields, particularly when plants are young. Older plants are more tolerant of defoliation.
How to protect your garden from slugs
If slugs are a problem in your garden, it's best to use a variety of steps to reduce their numbers. Damp conditions caused by excessive shade or poorly draining soil can increase slug numbers.
- Look for slugs under plants where they are shaded, cool and protected.
- The risk of slugs feeding is greater in times of cloudy and rainy weather.
- Slime trails are signs of slug activity.
- At night, use a flashlight to locate the slugs.
Discourage slugs by creating lighter, drier conditions.
- Trim low branches on trees and shrubs to allow more sunlight to reach the plants and soil.
- Divide or thin the plants to improve air circulation, allowing the soil surface to dry.
- Stake the plants and prune the lower leaves to lift the plants off the ground and away from slugs.
- If planting in rows, make rows of narrow plants (12 to 18 inches wide).
- If the soil is consistently wet, improve drainage by amending the soil with compost.
- While cut leaves make an excellent mulch, too many can enhance slug habitat. Remove and fertilize any extra leaves in the spring.
- Remove or relocate materials where slugs hide, such as containers, boards, pavers, and flat stones.
Grow a water efficient garden
- Slugs are active at night; water the plants in the morning so that the water is absorbed and the plants dry out.
- Water the root zone at the base of the plant.
- Avoid overhead watering.
- Irrigate by hand or use drip irrigation or soaker hoses.
- Do not water leaves, flowers, fruits or vegetables.
- Plants for drier conditions and full sun (more than 6 hours of sun):
- Perennial plants: yarrow (Milenrama), ajejo (mugwort), serralha (asclepiasspecies), asters, coneflowers (Equinácea, Rudbeckia), resistant mothers (Dendrantemaspecies), ornamental grasses, lily, Shasta daisy (proud leucanthus), gay grief (liatris), lily (lily), bee balm (Monarda), flake (Phlox maculata, i), balloon flower (Platycodon), wise (sage), mason (sedum), painted daisy (savings), false lupine (thermopsia), tulips, daffodils, crocuses and other early spring bulbs
- Ornamental grasses: blue oat grass (Bouteloua), rush (Calamagrotis), bloodgrass (commanded), moorgrass (Molinía), needleweed (Panic), font grass (Pennisetum), meadow seed (Sporobolus heterolepis)
Grow shade plants that slugs don't like
- For full shade (more than 6 hours of shade):
- Perennials: Creeping Phlox (floxstolonifera), forest phlox (Phlox divaricata), bleeding heart (dicenter)
- Ornamental grasses: tufted grass (Deschampsia), hakone grass (Hakonechloa)
- sedge: gray sedge (Carex gris), Pennsylvania sedge (C. pensylvanica), Japanese sedge (C. morrowii), banana sedge (C. banana)
- For light or partial shade (3-4 hours, dull sunlight):
- Perennial Plants: Aconite (Aconite), the lady's tablecloth (alchemy), aquilegia (aquilegia), marsh milkweed (red milkweed), false spiral (Astilbe), turtle head (Quelona), bugbane/snakeroot (atos), rosas (clove), purge (euphorbia), geranium (Geranium), coral bells (Heuchera), Mint (nepeta), primrose / sundrops (Oenothera), spider (Tradescantia)
- Ornamental grasses: oat grass (helicotricon), rush (Calamagrotis), blue fescue (glaucous fescue)
- sedge: blue sedge (carex flaca), rush (Carex muskingumensis)
- Clematis: Grow this flowering vine on a trellis or fence in full sun, but with the base of the plant in cool shade.
- Slugs generally do not damage trees and shrubs.
Harvesting plant slugs by hand
- Look for slugs on the surface of leaves and under leaves, as well as under rocks and debris.
- Drown the slugs in soapy water or mash them.
Lay several flat boards, tiles, or damp newspapers
- Check under these traps the next morning and kill any hidden slugs.
- Repeat this step night after night until the slug damage is no longer present.
Set beer traps
- Bury the containers in the ground so that the top of the container is level with the ground.
- Pour beer or yeast water mixture (one teaspoon of yeast to three ounces of warm water) or similar fermenting liquid into bowl 6 to 7 inches deep. The liquid should be about an inch below the top of the pot.
- Attracted by the smell, the slugs fall into the liquid and drown when trying to drink.
- Check the traps at least several times a week and clean and replenish them as needed.
- Be sure to place enough traps to protect the entire garden, especially when slugs are numerous.
Copper has been shown to deter slugs by reacting with their mucus, giving the slugs a sort of electric shock. Copper sheets or bands can be used horizontally or vertically, but must be wide enough to accommodate the entire block.
Not all copper strips or tape sold for slug control are wide enough to be effective. This type of copper barriers are the most practical for small gardens and containers.
Careful:The sharp edges of some products can cause safety issues, especially for young children.
Diatomaceous earth (tiny fossilized skeletons of ancient water diatoms) is thick and can scratch slugs. It is most effective when used in dry conditions and has little effect in absorbing moisture. It is generally not an effective slug deterrent.
There are many types of animals that eat slugs: beetles (ground beetles, wandering beetles, fireflies), frogs, snakes, turtles, shrews, ducks, starlings and other birds.
Encourage these natural enemies when practical in your garden.
Keep in mind that using pesticides to kill slugs can also harm these natural enemies. If you use chemicals for other problems, treat minor pest problems or use bait.
If non-chemical steps do not reduce the damage done by the slugs, baits are available to treat them with a pesticide.
- Apply the bait in the late afternoon or early evening when the slugs are active.
- Sprinkle the bait around the plants being protected.
Iron phosphate is a stomach poison that damages the slug's digestive system.
- It is a less toxic bait for slugs; It presents no problems when used around children and pets.
- The slugs stop feeding several days after eating iron phosphate and eventually die (up to seven days).
- Iron phosphate is effective for two weeks, even if it gets wet.
ferric sodium EDTA
- A less toxic product similar to iron phosphate.
- It works faster, killing slugs in just a few days.
Metaldehyde is attractive and highly toxic to dogs and other animals, so avoid using this product if pets are likely to enter a yard where this bait may be applied.
- When slugs eat metaldehyde, it quickly dehydrates and kills them.
- Metaldehyde is most effective during hot, dry weather.
CAREFUL:Mention of a pesticide or use of a pesticide label is for educational purposes only. Always follow the instructions on the pesticide label that is attached to the pesticide container you are using. Make sure the plant you want to treat is listed on the pesticide label you plan to use. And watch the number of days between applying pesticides and when you can harvest your crop. Remember, etiquette is the law.
Authors: Julie Weisenhorn, outreach horticulture educator and Jeff Hahn, outreach entomologist
Revised in 2020
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