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Tiny Game Hunting
Environmentally Healthy Ways to Trap and Kill the Pests in Your House and Garden
Hilary Dole Klein and Adrian M. Wenner
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Probably
the most loathed pests in the garden, slugs and snails both eat large
ragged holes in plants.
They'll eat the whole plant if it's young and tender, and their destructive
chomping and silvery trails are a dead giveaway to their presence. ClassiŞed
as gastropods, meaning "stomach foot," they're fun to hate and easy to
kill, but maddeningly difficult to control. Because many species came
from elsewhere, there aren't enough natural predators to cope with them
in North America, and we humans have to step in.
The chief difference between a slug and a snail is that slugs lack the spiral shell that snails tote around. The brown garden snail was introduced in this country in San Francisco in the 1850s by a Frenchman who thought he could get people there to eat them. He was wrong, and if they didn't catch on as food in San Francisco, there was surely no hope of them doing so in the rest of the country. Undaunted, the brown snails set out on their own to conquer America and have succeeded so far in becoming the most common snail pest in California. Several species of slugs range from a quarter of an inch to six inches in length and are gray, brown, yellow-ochre, and spotted. Since each slug is both male and female, they have no trouble finding mates, and both of them can get pregnant! They can lay 100 eggs in a season, and in dry times they can hibernate for years. They are capable of eating thirty to forty times their body weight each day. They range throughout North America.
Snails
are mobile creatures and can travel a mile in about fifteen days (although
they don't). Slugs are almost twice as fast, able to travel the same distance
in eight days. In your garden, a snail may travel a hundred feet for a
meal.
Both slugs and snails hide during sunny days in shady, preferably moist spots under leaves, rubble, stones, and garden debris. They congregate and breed in certain plants, among them agapanthus, lilies, irises, ice plant, ivy, nasturtiums, jasmine, and strawberries. They also favor soft, moist mulch.
Barriers
Keep in mind
that slugs and snails have their place as food for other animals and birds.
They are also recyclers (even of dog droppings), and they produce humus.
So barriers are perhaps the most benign form of control. The tender, soft,
slimy bodies of slugs and snails need a fairly smooth surface on which
to travel. (Can you imagine trying to navigate your garden on your tongue?)
Their trails, in fact, are self-created roadways laid down with mucus,
which is why barriers can stop them.
Good barriers can consist of wood ashes, crushed oyster shells (from feed stores), crushed eggshells, diatomaceous earth, sawdust, lime, short hair clippings, powdered ginger, bran, and ammonium sulfate. Make sure the barrier is at least three inches wide--the wider the better. If a powder barrier gets wet, it will need to be replenished. A border planted with low, spreading rosemary is another one they won't want to cross.
Garden centers sell snail barriers, some of which resemble strips of sandpaper; others have salt embedded in the material. Copper strips make the best barriers. When the slimers touch the copper, it shocks and repels them. These strips are also effective as barriers on trees. Snails love citrus trees and can be real pests in orange groves. Copper comes in sheets, strips, and sticky-backed tape. One gardener glues copper pennies around her pots.
A
good mulch of oak leaves will also repel slugs and snails. Gather seaweed
and spread it around as a mulch. Not only does it makes a good barrier,
but it will also be good for the soil. If you use decorative mulches,
choose cocoa hulls or crushed rock, which are quite inimical to slimers.
To protect new seedlings from voracious slugs and snails, cover each one with a topless plastic soda bottle with the bottom cut off.
Old window screens (or new screening) can be cut into snail barriers. Copper screen would be ideal. Make a slit from one corner of a ten-inch square of screen and cut out an opening for the plant. This is even more effective if you shred the edges of the screen by removing a few wires from the perimeter.
Handpicking
For major snail or slug infestations, the best method of control is handpicking.
Because these creatures are nocturnal, begin collecting them about two
hours after sundown. Watering late in the afternoon will make them more
active. Get your family together and give everyone a strong flashlight.
Children are easily motivated by a monetary reward in these matters.
For handpicking slugs, use tweezers, kitchen prongs, an iced-tea spoon, or latex surgical gloves--cheap and disposable. Equip everyone with buckets or jars filled with water and a little vinegar or ammonia. Then dump the critters on the compost heap. (Salted or soapy water will also kill them.) Or crush the snails and bury them where they will add nutrients to the soil. Even better, if you have a pond with turtles and fish, heave them in.
At first go out several nights in a row. Not all slugs and snails venture out to pillage every night. When the infestation has been controlled, you will only need to go out about once a week.
Salting
and Squirting
If slugs are your chief problem, and you don't feel up to handpicking
them, tape closed all the holes of a saltshaker except one. Sprinkling
a slug with a few grains of salt will cause it to crawl out of its slime
coat. Then apply a second time--this is the lethal one. If you are worried
about adding salt to the soil, try sprinkling the offenders with ammonium
sulfate, which both kills them and fertilizes the soil.
A squirt bottle filled with a mixture of equal parts water and vinegar or water and ammonia will finish slugs o¤ in one squirt. It works on snails extended out of their shells too.
One of the most time-honored ways to get rid of slugs and snails is the beer trap. Take a small container like a cat food can, or--if you are convinced your garden is infested with giant snails--a pie tin. Bury it so the top is level with the ground and fill it with beer.
The
brand of beer does make a difference. We once bought the cheapest beer
we could and succeeded in catching exactly one slug with the six-pack.
An entomologist at Colorado State University, Whitney Cranshaw, conducted
a beer tasting for slugs in 1987, killing 4,000 of them in eight weeks
in the name of scientific inquiry. Kingsbury Malt Beverage attracted the
most, but Michelob and Budwieser fared well too. The yeast in the beer
is what attracts the varmints, while the alcohol befuddles them and makes
it harder for them to climb out. Beer is most effective in the first twenty-four
hours.
Another trap makes use of yogurt or cottage cheese containers with one-inch holes cut out around the sides, several inches from the bottom. Pour in the beer and wait for the creatures to crawl in. The lid on the container means the beer won't evaporate, and the dog can't lap it up.
Another way to keep the dog out of the beer is to use a beer bottle with a little beer in it, laid on its side with the lip at ground level. This is best for slugs and smaller snails.
Here's a bait that is cheaper than beer and takes advantage of the slimers' attraction to yeast. Mix two tablespoons of flour with a teaspoon of baker's yeast and a teaspoon of sugar in two cups off warm water. Or take two cups of grape juice and add a teaspoon of yeast and fill a container. One thing about these traps that is horrid but effective: slugs and snails are attracted to the dead bodies of their own kind.
If you provide slugs and snails with hiding places that they will seek out when morning comes, you can go and pick them off at your leisure. They will more likely go into your shady traps if you eliminate the other hiding places and debris that they favor. Traps can be made from shingles, small boards, or overturned clay pots propped up a little on one side. Two-gallon nursery pots can be stacked together and laid on their side, with a little space between the bottoms. Plastic lawn and leaf bags or damp burlap can also be used to attract slugs and snails. It helps if you dampen the ground underneath first.
Set out grapefruit or orange rinds, propped up with a small stone. Or use banana peels; slugs will be attracted by the odor and crawl underneath. Other suitable hiding places include cabbage leaves, lettuce leaves, and potato slices. Slugs and snails are also drawn to raw bread dough, dry dog food nuggets, and fallen hibiscus blossoms.
Long boards laid down between garden beds and slightly propped up with pebbles will attract slugs and snails. An effective trap devised by entomologists at the University of California at Riverside consists of an untreated board (between twelve and fifteen inches square) with one-inch wooden strips nailed on two sides to prop it up. Redwood makes a very durable trap. Crushing a few snails on the underside of the board will draw in others.
Many slugs hide in the soil, so rototilling is a good way to get rid of them.
Natural
Enemies
Many beetles prey
on slugs and snails, including rove beetles, carrion beetles, soldier
beetles, and a big impressive specimen called the devil's coachman. In
a greenhouse where slugs are a problem, the ground beetle can be brought
in to do slug duty. This beetle hunts all night and hides during the day.
Outdoors, other natural predators of snails and slugs include chickens, ducks, and geese. Toads (the best), frogs, box turtles, skunks, shrews, opossums, rats, moles, birds, snakes, and lizards will also eat slugs and snails. Certain şies will prey on them, as will centipedes.
Birds will be more likely to eat snails if you provide them with a big şat stone that they can use to crack the shells on. Scatter birdseed around the garden to encourage birds to poke around.
The
decollate snail, Rumina decollata, a somewhat smaller snail whose shell
looks like a seashell, is the most effective natural enemy of the brown
garden snail. In Southern California, a number of gardeners and citrus
growers have successfully imported these snails to control the brown garden
snail. Check with suppliers; they are not allowed in some California counties.
Decollate snails have the same requirements for moisture and the same nocturnal habits as the snails they prey upon. They may eat an occasional tender leaf in contact with the ground or a fallen bruised fruit, and they can be hard on some low-growing plants. But this snail actually prefers decayed vegetation, and it will not eat the healthy leaves in your garden. It does not do well in dry places, so if you order these snails, try to provide some sort of damp haven, just as you would for a toad or frog. The decollate snail does its best job on smaller snails, so you will still need to handpick the bigger snails in your garden. And it may take them a few years to eradicate the brown snail, so use barriers, not poison!
Poison
Snail poisons and
bait in the form of powders, pellets, and goo have been dumped on yards,
gardens, and public landscaping by the ton. The empty snail shells leave
proof that these poisons work. But what else are you killing when you
kill snails in this way? Earthworms, for one thing, are very vulnerable
to certain snail poisons. And earthworms are said to deter slugs and snails,
because their castings are inimical to them.
Birds have been other victims of snail poisons. Starlings, for example, which eat garden snails, seem to avoid gardens where poison is used. You also run the risk of poisoning your own pets and even children, since some pellet baits are attractive to them. Furthermore, certain poisons are absorbed by plants that we eat and can thus poison us.
Look for snail baits containing metal aluminum ions or iron phosphate. They take several days to work, however, so don't use them the same day you set out your tender new seedlings.
Resistant
Plants
Here is a list of
some of the plants that snails and slugs don't seem to like: azaleas,
basil, beans, corn, daffodils, ferns, freesias, fuschias, geraniums, ginger,
grapes, holly, lavender, mint, parsley, rhododendrons, roses of Sharon,
sage, and sunflowers.