Nature Notes
Slimy Garden Slugs Will Succumb to Traps or Predators
By Patricia Martin

As my 11-year-old nephew put it the other day, I "got slugged." No, I wasn't struck by anyone. I picked up a bag of cedar mulch to put around a garden, and began distributing it with my young relative when I looked down. On my shirttail, one of the larger slugs I've seen, about four to five inches long, was stuck, oozing slime all over my shirt. My nephew laughed, as 11-year-old boys love things that are gross, and we flicked it off the material and it fell into the garden. As I'm not fond of slugs in my garden, I picked it up with a trowel and threw it onto the road. A short time later, I looked and the slug had been dispatched by a bike tire. After finishing gardening, I went inside to change my shirt and to try to remove the slug slime. We worked on it with water, just rinsing it, and we worked on it with a knife, scraping it off, and that worked better than just water. We worked on it with a scrub brush and dish soap and finally most of it was removed. I then laundered that shirt. I never knew it was that difficult to get rid of slug slime. I guess that slugs and slug slime are just a fact of life around here in the summer.

Slugs are one of the most common garden pests. They're often thought of as snails without shells and that description is not far off, as they're closely related. These organisms are mollusks and are in the class Gastropoda. Gastropoda literally means "stomach foot," which makes sense since the major feature of the slug, or snail for that matter, is a muscular foot. In addition, in the slug there is a flap of skin called the mantle, where the shell would be if a slug had a shell. The slug can draw its head in under the mantle. On the head it has two sets of retractable tentacles. The longer, upper set holds simple eyes at the end, which enables the slug to see light and dark, and the shorter, lower pair holds scent receptors. Slugs come in a variety of colors from pink, brown, beige, black, and gray, with or without spots. Around the Island the most common color is brown or almost black. Of course, the other characteristic of the slug is slime, lots and lots of slime.

Slime indeed has a function - it allows them to move. They produce a pool of slime, which allows their muscular foot to inch along the ground by means of muscular waves. You often notice their presence in a garden by the silvery trail of slime that is left behind when they pass. To prevent them from drying out, slugs require moisture and shade and generally creep through shaded lower leaves of plants. Because they lack both a shell and a skeleton, slugs are able to squeeze into small dark places to find shade. Many slugs, especially the types we have around here, like to eat young, tender vegetation or decaying vegetable matter. They shred their food and ingest it by using a radula, a conveyer-belt-like organ covered with thousands of sharp, tiny teeth. One reason that we notice these creatures is that they reproduce at a terrific rate. Slugs are hermaphrodites, having both female and male reproductive parts. They cannot fertilize themselves, however. As usual, it takes two to tango, and they can begin the dance at three months of age. It can take a full day for slugs to mate, but when they separate, each of them can produce hundreds of eggs, which will hatch in only three weeks. The eggs are tough and elastic and not very vulnerable to small predators, but they can dry up if not kept moist. These organisms have no larval stage and so the young slugs look like miniatures of the adults.

There are a number of ways to control slugs in the garden. One way is to remove decaying vegetation that they like to eat so much. Some mulches around plants can be used as a barrier because slugs don't like to crawl over rough or irritating surfaces. Eggshells, wood ashes, gravel, sand, oak leaves, cedar or oak bark, and tobacco stem meal have been tried to keep out slugs. Finely chopped hair placed around beds has been used to discourage slugs and snails, as the hair irritates the skin of the organism. In order to get rid of the irritant, the slug or snail over-produces slime and may cause itself to dehydrate and die. It is also thought that inter-planting Prostrate Rosemary or Wormwood will help repel these pests.

There are some organisms that eat slugs, and some people like to encourage them in their gardens. These predators of slugs include moles, shrews, goslings, ducks, and my favorite, garter snakes. I have a pair of garter snakes that live in my backyard, and for their love of eating slugs, I leave them be.

There are a number of sprays that can be squirted directly on slugs to kill them. Many of them are very easy to make. A 50 percent solution of vinegar and water is effective, or lime juice will work when sprayed directly on the slug.

The most commonly known is the beer trap. Abeer trap consists of a shallow dish, like a pie plate or a tuna can. An inch or so of the brew is poured in and the tin is placed in a shaded spot where you think slugs may be. Press the dish down into the soil until the rim is at ground level. The slugs fall in, get sloshed, and die. Near beer (low alcohol) seemed to be preferred by slugs in the only study that I've seen on the subject. Michelob and Budweiser were runners-up. If you don't want to waste beer on slugs, a fermented brown sugar yeast mixture will work, or cider vinegar mixed with sugar.

A number of years ago a friend taught me a silly song about slugs, which was supposed to make me appreciate them. It goes "Mackinac slug, Mackinac slug, when some people see you they say ugh. Mackinac slug, Mackinac slug, when I see you I give you a hug."

I don't know about you, but after my most recent experience with slugs and my shirt, I'm never going to hug them.

Trish Martin is a yeararound resident of Mackinac Island, has earned a master's degree in botany from Central Michigan University, and owns Bogan Lane Inn.