Slug and snail baits: How to safely fight the war on slime

Strike up a conversation between people who garden in "cool" climates and within moments the word "slugs" will pop up. It's enough to shift a casual chit-chat into a strategic planning session.

Gardeners agree that slugs are a menace, but they are often confused about which tactics to employ. While Picking slugs is one of the most effective methods to reduce the adult breeding population, sometimes in the heat of the battle you need to attack on more than one front. Here's the scoop on slug baits, including a different twist on the war against garden mollusks: Coffee.

Many commercial slug and snail baits are available today as pellets, meal, or emulsions. The two most popular baits that are currently licensed and formulated into baits for use on home gardens are:
+ Metaldehyde
+ Iron phosphate

Most chemical baits combine an attractant, usually apple meal or some other sweet-smelling base (more on that later) with an active chemical compound such as metaldehyde, to poison whatever swallows the bait. Products containing varying concentrations of metaldehyde include: Cory's Slug and Snail Death, Deadline, and Slug-Tox.

Metaldehyde, which has been used since the 1930's, works by dehydrating its victims. These products are sold as granules, sprays, dusts, pelleted grain or bait. They are usually applied to the ground around plants to attract and kill slugs and snails.

Metaldehyde is classified by the U.S. Environmental Protection Agency (EPA) as a "slightly toxic compound that may be fatal to dogs or other pets if eaten." Many vets have experience with dogs ingesting metaldehyde baits.

According to the Field Guide to the Slug (Sasquatch Books) ingested metaldehyde can lead to nervous system damage or death in humans and other animals."The threshold for tolerance is related to size, making birds and small mammals especially vulnerable." Bottom line: if you decide to use poison baits, do so with extreme caution, especially about edible plants, and READ THE LABEL.

Iron phosphate slug and snail baits are much different than chemical warfare. For one thing, iron phosphate is a compound that occurs naturally in the soil.

Products containing iron phosphate include: Sluggo and Escar-Go! (available through GardensAlive!). Iron phosphate products are a pelleted bait, that resembles grains of rice. They're a blend of iron phosphate (the "active ingredient") which is then coated with an attractant (bait). Slugs and snails are attracted to the bait more so than plant (I've witnessed this personally!), even luring them from their hiding places.

According to one set of instructions, this is how a product like Sluggo works. "Ingestion, even in small amounts, will cause them to cease feeding." Or, as one gardener-friend put it, "They crawl away and die, and you never see them again."

Unlike Deadline, Sluggo granules can be used around domestic animals and wildlife. It stays intact for a week or two, even after waterings or several rains, and provides protection to greenhouse plants, container gardens, vegetables, flowers and fruiting plants and shrubs. Manufacturers of iron phosphate baits claim they are non-toxic around children and pets, and are much safer to use than those baits containing metaldehyde.

SKIP THE SALT
Many gardeners have sprinkled a dash of salt on a slug at least once. This is not a good thing, as the salt can make the soil toic to all but a few salt tolerant creatures and plants.

According to Nature magazine, we have another weapon in the eternal battle against slugs and snails: the double espresso. Slugs and snails hate caffeine, researchers have discovered. The chemical could become an environmentally acceptable pesticide.

Robert Hollingsworth of the United States Department of Agriculture's Agricultural Research Service in Hilo, Hawaii, and his colleagues were testing caffeine sprays against the coqui frog, an introduced species that infests potted plants.

They also noticed that a 1 to 2 percent caffeine solution killed nearly all the slugs and snails within two days. Concentrations as low as 0.01 percent put the pests off their dinner. A cup of instant coffee contains about 0.05 percent caffeine, and brewed coffee has more.

?This sounds like scientists chatting around the water cooler, so let's look at a more real-life example: A cup of drip brewed coffee has about 115 milligrams of caffeine, an espresso (and percolated coffee) about 80mg, while instant coffee has about 65mg of caffeine. Thus, drip brewed coffee is about twice as strong as the instant stuff, which means you want to use drip brewed coffee for repelling slugs and snails.

Coffee grounds are already recommended as a home remedy for keeping slugs and snails at bay. Grounds repel slugs, Hollingsworth found, but a caffeine solution is much more effective, he says: "Slugs turn back immediately after contacting the [caffeinated soil]."

Personally, I've had good results (if you want to call making a slug uncomfortable "good results") with sprinkling coffee grounds around plants as well as spraying slugs with brewed coffee--you know, the stuff that doesn't get consumed in the morning and tastes really bad when you try to microwave it in the afternoon? Many other gardeners have told me they've had similar luck.

Well, caffeine is an alkaloid compound that acts as a stimulant in humans. Alkaloids are usually derivatives of amino acids and most alkaloids have a very bitter taste. Just think about your first taste of coffee. Pretty bitter, wasn't it? Caffeine is found in the beans, leaves, and fruit of over 60 plants, where it acts as a natural pesticide that paralyzes and kills certain insects feeding on the plants.

Bottom line: caffeine is more effective against slugs than metaldehyde products. The United tates bans metaldehyde residues in food, but classifies caffeine as safe. It may even qualify as organic, adds Hollingsworth. "I would expect caffeine applications to kill small snails and slugs, and repel the larger ones," says Hollingsworth. He envisions it being used in greenhouses and on fruit and vegetable crops.