News

Another Snail in the Coffin of Your Garden

July 22, 2015 7:58am
Image: Scot Nelson

Image: Scot Nelson

Dahlias can barely get growing. Hosta leaves are riddled with ragged holes. Dreams of magnificence chomped away while you slept. If you’ve gardened in Green Lake for more than a season, you already know the ravenous slimy, culprits: slugs and snails.

slug-snail

Maybe you’re thinking “live and let live,” or “let nature take it’s course.” Meanwhile, chew on these tidbits:

  • An adult slug will eat 40 times its weight each day
  • Being hermaphroditic each slug produces up to 500 eggs in its two-year lifespan.
  • Slugs remember where the goodies are and will return another night to finish off tasty seedlings until they are all gone.

Source: Seattle Times article by Valerie Easton

  • And no, the ones here are not the edible escargot, though apparently they were introduced from France with such a thought.

Brown garden snails, Cornu asperum, are the ones we commonly see in Seattle. Other than the shell, they closely resemble their slug cousins, and behave identically.

So, you really, really don’t want them in your yard. What to do about them?

Avoidance:

Feeling squeamish and/or benevolent, I have thrown snails to the curb and in my yard waste bin, but really I was just sidestepping the problem and moving it around. Do NOT put them in your compost bin unless you are trying to breed a slug nation.

You could put them in your yard waste, I suppose, which is like giving them a vacation before the end. (Seattle’s yard waste goes to Cedar Grove Composting, which cooks it at 150 degrees for three days, the web site says.)

Barriers:

Make your place less welcoming. Clear up debris, boards, mulch, empty pots, which are favorite hiding spots.  (For me, this is not going to happen. I prefer a naturalistic garden style – which admits kids will be leaving bats, balls and more outside, and I will leave garden flats around for days.)  Plant unfriendly plants – scented herbs, plants with thick foliage. Here’s a list of slug-resistant plants. If you must have hostas, dahlias and peas, plant them up high in pots and consider surrounding by Maginot lines of crushed egg shells or copper stripping at least three inches wide (six is better).

Contract a hit:

Beneficial nematodes, several beetles, many birds including ducks and chickens, garter snakes and even one of their own species – the decollate snail – are natural predators often suggested to winnow mollusk populations.

Nematodes work for about six weeks, but unfortunately, also kill beetles, which then lays the groundwork for an onslaught for the next breeding cycle. Ducks and chickens, after eating mollusks, will likely also eat your peas and lettuce as a garnish. Decollate snails are labelled as invasive and cannot be imported here, and snakes? Nuff said.

Go Rambo:

Sources agree the most efficient time to nab slugs and snails is in early spring to get as many adults as possible, since they do the most damage. They are most active in the evenings and in cool, wet weather.

In dry weather you can call them out by watering in the late afternoon and hunting under pots, piles of debris, under decks, etc., with a flashlight, gloves and/or chopsticks.

Then you can either: drop into a jar of soapy water, smash with your shoe, or cut in half with pruners or a knife. Skip the salt-sprinkling and beer traps you may see recommended. The first is inhumane, and hurts your soil, and the second is messy and difficult to do effectively. For more see King County’s take on snails.

Chemical Controls:

Slug bait. Everyone agrees the newer, “organic-labelled” iron phosphate baits are a huge step above metaldehyde ones. However, whether Sluggo and Escar-go are really OK for children, pets and wildlife is still in question. That’s because iron phosphate is non-toxic, but another ingredient, a chelate named EDTA, not listed on the label, is potentially dangerous in combination with iron phosphate if ingested. Here’s a blog post by Jeff Gilman for Washington State Extension, which includes links to a study of dog poisonings from this combination in Australia.

If you use these baits, they need to be applied after a rain or on wet ground, and every two weeks.

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