Commercial Brands Are Toxic After All
Slugs are the Northwestern gardener’s worst pest, followed distantly by aphids. For years, I’ve promoted the use of Sluggo and other iron phosphate-based slug baits as a safe, nontoxic alternative to metaldehyde baits, which harm or kill all kinds of critters from wildlife to pets. Ironically, I’ve recently learned that in fact, Sluggo and its kin kill earthworms (which metaldehyde baits don’t) and can also make dogs, cats, birds and other critters ill. More and more veterinarians are coming out with stories of poisoned pets (though few if any fatalities), but our beloved earthworms might need their own lobby to speak out for them.
So how does this soft of situation come about? Legal loopholes make it possible for manufacturers to provide required toxicity information on single ingredients but not on a blended product. Thus, the result of chemical interactions are not always called out, and an ingredient can be listed as inert rather than active even when it does interact with another. Sound stupid? Well, it is, and many other countries don’t manage dangerous substances this way.
Sad News About Slug Baits
Here’s the sad story with Sluggo and its ilk: Iron phosphate is listed as the active ingredient, even though by itself it is not actually toxic. Like so many gardeners, I believed the party line about these baits, which was that iron phosphate is safe for vertebrates but not for molluscs. As I now know, by itself, iron phosphate is NOT toxic even to molluscs. In order to make the iron phosphate toxic, manufacturers add a very commonly used substance called EDTA (because who wants to say Ethylenediaminetetraacetic acid?). In itself also largely harmless, in combination with iron phosphate, EDTA creates iron toxicity not just in slugs and snails but in cats, dogs, birds, and more. Worse yet, it kills worms outright.
Recognizing this, some countries insist that EDTA be labeled as an active rather than inert ingredient, making these baits ineligible for organic certification. In the US, there have been several unsuccessful attempts to get such baits de-listed, but when they encountered significant push back from manufacturers, they were dropped.
Our native slugs are nature’s composters, feeding mainly on decaying foliage and important in the forest biocycle. Most garden damage is done by Euro-trash, since about 16 slug species and 28 snail species have invaded the maritime Northwest. Since commercial slug baits are no longer a safe option, we can fall back on the time tested techniques we all used to use. All those old tricks still work, from letting ducks and chickens forage in the garden to spreading diatomaceous earth around susceptible plants.
It has also been discovered that strong coffee can deter the highly destructive baby slugs, which are hard to control since they are not attracted to baits of any kind. As little as 0.01 percent (1 part per ten thousand) caffeine keeps slugs off foliage plants. Higher concentrations of 1 to 2 percent (1-2 parts per hundred) kill slugs and snails outright. The average teaspoon of instant coffee contains about 0.05 percent caffeine, which works great for sluicing off tender foliage. To pick off slugs, make a lethal house blend with cheap-o instant coffee and fill a squirt gun. I used to pay my kids a penny a slug and they easily made a dollar before breakfast each morning.
Zapping Also Works
Copper strips can also ward off slugs because a biochemical reaction between the copper and the salts and acids in slug slime electrocutes them. Keep slugs out of large pots by wrapping the pot base in copper sheathing. In the garden setting, it’s less of an option, since slugs and their eggs may be almost anywhere. BY surrounding raised bed with copper strips, we may simply be keeping slugs and/or their potential offspring IN the garden we want to protect.
Perhaps the simplest slug controls are halved grapefruit rinds set in the ground and filled with beer. Independent tests (mine) showed that St. Pauli Girl dark is the most slug-attractive, but pretty much any kind will do. Small jars set into the ground at an angle and partly filled with beer (even flat dregs) also work, drowning slugs in presumable bliss. Teetotalers can make an attractive bait using simple kitchen ingredients as well:
Safe Liquid Slug Bait
1/4 cup sugar
1 teaspoon baker’s yeast
1 cup warm water
Mix ingredients in a jar and let stand 20 minutes before using. Makes about 1 cup.
Swiss Investigation for Organic Certification:
Sluggo Label and Advertising:
NY Department of Environmental Conservation Statement:
Australian Article with Mode of Action for Iron Chelate products:
Dr. T’s Nature Products Slug and Snail Killer:
National Organic Standards Board review of product: