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Marin IJ Articles

Snails and slugs

  • Juliana Jensen
  • You're out in the garden on a nice evening when there it is, the unmistakable slimy mucus trail. You see your favorite hosta full of holes. You cautiously turn over the leaf and there it is waving its cockeyed eyeballs in every direction. It's a snail. And it's just eaten your favorite plant.

    Snails came to California from France in the 1850s, imported by gourmands with a yen for escargot. Slugs and snails are most active at night and on cloudy days, hiding in shady spots during the heat of the day. When it's cold they hibernate, sometimes attached to trees or walls.

    A snail can lay 80 eggs up to six times a year, while a slug usually produces three to 40 eggs at a time. Since they are hermaphroditic, meaning that they have both male and female reproductive organs, they do not need to find a mate in order to produce fertile eggs. These gastropods use mucus to slip along on their "stomach feet," creating the silvery trails that glow up at us at night. Slugs and snails are similar biologically, except that the slug doesn't have the distinctive outer shell of a snail.

    You can recognize snail and slug damage generally by the smooth-edged, irregularly shaped holes they make in leaves, flowers or succulents. Sometimes it is difficult to differentiate damage caused by snails from damage caused by insects such as caterpillars or earwigs. The clearest way to tell is to spot the slime trail on or near the damaged plant. It is important to determine the type of creature causing the damage in order to take the proper management steps to eradicate it.

    There are several steps you can take to reduce your snail and slug population. First, you can clean up any debris where they hide. They can hide under stones or wood, under low-growing branches or in ground covers like ivy.

    Vegetable gardens or snail favorites should be placed as far away as possible from typical snail hiding places. Switching from sprinkler to drip irritation system reduces the humidity in a garden and makes it less hospitable to snails.

    A copper barrier can help reduce snail and slug damage. Copper foil can be applied around the tops of planting boxes, just make sure there are no snails trapped within the perimeter. If you are concerned that there may be snail or slug eggs in the soil, you can solarize the soil by putting a clear plastic tarp over the soil for six weeks in late June or July, but only if you have no living plants in that soil. This is a good thing to do in winter when the soil is fallow, but it may take longer than six weeks if there is not as much sun.

    Luckily, snails and slugs have many natural predators. They provide meals to beetles, snakes, toads, turtles and birds. Ducks, geese and chickens find snails and slugs to be delicious treats, but then, they also like seedlings, so it can be a mixed blessing to have them tottering through the garden.

    The hunters among you can handpick the snails you find at night using a flashlight and rubber gloves. Destroy by crushing and dispose of the snails.

    One of the most effective ways of controlling snails is through careful plant selection. Snails and slugs enjoy soft-leaved, herbaceous plants like basil, beans, cabbage, dahlias, delphiniums, hostas, lettuce and many other vegetables and low-growing berries like strawberries. A few soft-leaved species such as begonias, poppies, fuchsias, geraniums, impatiens and nasturtiums are resistant to snails. In general, snails dislike grasses, plants that have rigid leaves and woody fragrant plants like rosemary, sage and lavender.

    If all else fails, you can bait for snails. The safest method is to use iron phosphate baits available at any garden store because they are safe to use around children, pets, and wildlife. Water the garden before you apply the bait in order to encourage snail activity. The bait causes the snails to stop feeding. You may miss the slime trails, but your garden will be happier.