The Ten Most Un-Wanted Pests

Introduction to IPM

Winter Moth
Root Weevil

Himalayan Blackberry

Black Spot

Powdery Mildew

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Aliases Slick, Garden Slug, Deroceras reticulatum, European Slug, Arion ater

Hangout: Under rocks, flower pots, other damp locations; also in tall grass, weeds
Physical Features: Soft bodied; similar to snails with no shell; 1/4" to 10" long; eyestalks that look like antennae.

Life Cycle
On cool, rainy days and nights, slugs point their gruesome looking eyestalks in the direction of your garden. Their subtle, slow movements belie the unsightly destruction they can cause to plant leaves. Making slug populations even harder to control, they can reproduce at any time of year. Each slug has both male and female reproductive parts, so they cross-fertilize to reproduce. Three to 40 eggs are laid at a time. Up to 400 eggs can be laid by one slug each year! As long as the weather is cool and moist, eggs will hatch in just a few weeks, putting even more criminals on the prowl. After only three months, offspring can reproduce.

Go Get'em, Slugger!

1. Patrol the area

  • Patrol during wet weather.
  • Search slug hideouts, like shady spots and under rocks and pots.
  • Look for slug eggs (milky-looking, round, squishy eggs) in the soil of your garden bed. This will give you an idea of springtime populations.
  • Be on the lookout for silvery slime trails.
  • Record what you see. Estimate slug populations in a given area when you patrol to make comparisons of population growth easier.

2. Make a positive I.D.

  • There are many other species of slugs in this area, but the usual culprits in backyard crimes are the garden and European slugs.

3. Do a thorough background check

  • Slugs are attracted to a chemical given off by ripe fruits called ethylene. This same chemical is found in beer, which is why beer traps are so effective.
  • Slugs are also attracted to tender plants and seedlings.

4. Determine the danger level

  • Look at damaged plant leaves and estimate the percentage of the leaf that is missing due to slug bites.
  • Plants can bounce back from damage as long as it's not too much. How much is too much? Established, healthy plants can make a comeback from heavy assaults, while seedlings may be at risk after just a few bites.
  • Keeping track of the size of slug invasions will help you decide if the problem is getting better or worse.

5. Make a plan

  • Do-Nothing Method
    -Pay close attention to how much feeding damage your plant can tolerate.
    -In the summer you can count on drier, warmer weather to keep slugs in hiding, rather than hurting your plants.
    -Damage in the Fall is less of a concern
  • Manipulative Measures
    -Get rid of hideouts, like old pots, debris piles, and long grass, where slugs seek shelter when the weather turns sunny and warm.
    -Break out the S.W.A.T. team! Squish slug eggs. Use a shovel to cut slugs in half or maybe you can even squash them barehanded. Or stomp on them.
    -Drown the dastardly drunks in beer traps. Slugs will blissfully dive into partially filled cans of beer pushed into the soil, plunging to their deaths. Or cut a hole two inches above the bottom of a paper cup. Fill with one inch of beer and place near plants.
    -Are they always attacking the same type of plant? Get rid of it and you might get rid of your slug problem. Sometimes changing cultivars eliminates the problem. Slugs love most hostas, but they won't eat the blue cultivars.
    -Defend your plants with copper armor! Line gardens, containers or any outside plant with copper strips purchased in rolls from garden stores. The interaction of copper with the slime on their bodies gives slugs the willies!
  • Secret Agents
    -Beef up security by making your landscape appealing to slug-eating birds, frogs, and snakes (the Lake Whatcom area does not have poisonous ones). Set up birdhouses, birdbaths or maybe even a little pond with a waterfall.
    -Slug-eating ground beetles are mortal enemies to these intruders. Reduce your use of pesticides to keep them stalking slugs.
  • Armed and Dangerous
    -Non-chemical methods work well against slugs, but if you are determined to use something like commercial slug bait, use as little as possible. Follow directions on the label for use, storage, and disposal.
    -Put the bait in some kind of container, not directly on the ground, to prevent toxins from eventually seeping into Lake Whatcom.
    -Baits with ferrous phosphate as the active ingredient are less toxic than others that often contain metaldehyde, a nerve poison which is dangerous for cats and dogs.

6. Evaluate the results

  • Since slugs have plant preferences, record which plants were slugged and the extent of damage. Also keep a record of strategies you used and if they sent slugs on the run.

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For more information, contact Scarlet Tang or Todd Murray
WSU Cooperative Extension (360) 676-6736
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