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.
Click to access Ferric%20Phosphate%20to%20be%20removed%20Formal%20Rec.pdf
Click to access Crop%20Protection%2028.pdf
Swiss Investigation for Organic Certification:
Click to access FIBL_FeP_Jan06_E.pdf
Sluggo Label and Advertising:
Click to access sluggo_03_bilingual.pdf
Click to access ferramol%20brochure.pdf
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:
Hello Ann. The best slug baiters IMO can be made by melting 1-2 small holes in the side of a plastic container (cottage cheese, yogurt, etc). Put less than an inch of the cheapest beer, pop on the the lid and set out. They are waterproof. My hens love the marinated slugs. When my yard was part of the Manette Edible Garden Tour, I set out all those saved plastic containers&lids, a small butane lighter, and directions as a Make&Take. It was a big hit.
Thanks, Paula Wood
Great craft project, Paula, sounds like fun for kids, too…maybe with skewers instead if flame though…hmm, maybe adults make the holes and kids can decorate the traps…
I tried to weigh through all the links you posted and the research was not as cut and dry as your post makes it seem. The Ohio State research showed that, “These data together provide clear evidence that molluscicides containing iron phosphate combined with either EDTA or EDDS can have adverse effects on earthworm activity or growth and may possibly be toxic to them.” It did not say it outright killed earthworms.
Can you point me to the research that supports that notion? Maybe I just missed it.
I am a Master Gardeners and always want to be up to date with the latest research. Personally, I do not believe in using any pesticides.
Thank you for providing all the links.
I’d always rather be safe (and keep critters, water, soil, and air safer) than sorry, and I have indeed observed dead worms around baited sites, which I’ve also heard from several organic growers who no longer use slug baits of this type. Here’s some more recent info:
Hope this is helpful!
Chemical companies run the USA’s agricultural policy. Remember when they made videos showing kids in pools being sprayed with DDT? Nothing has changed.
Thank you Ann, for disabusing me of the notion that Sluggo use is ok! Even permaculture people have told me it’s an acceptable last resort. I was going to start deploying it this year, but think I will instead add to and enhance existing protections.
I’m pretty pleased with the beer traps, but sometimes use ground clam shells as well. It’s very annoying to lose plants to slugs but it feels worse to use poison (to me anyway). If you find something that works well, please let me know!
I am glad I read this! Trusting regulators seems foolish at best but I continue to think times have changed…. *smacks forehead* I have massive slug issues being on the very wet west coast. I will try beer bait and hope for the best.
Hi Raya, Sadly, trusting regulators is not always wise, as we have seen with the steady breakdown/destruction of the EPA, FDA, DNR and so much more in recent years. I am hopeful that we are once again moving in a positive direction but there’s so much to make up for, it’s no small or simple task. Sigh. But onward, right?
I was reading up on the ferric sodium EDTA bait research and the risk to non target species etc.
I did speed read but the most recent research from published scientific papers would seem to suggest that at the recommended rates and loading of a.i. the risk was perhaps not dangerous to other species.
Interested in your thoughts as you say in your article that this is not the case.
Clearly if the EDTA bait is ok to use then it is more efficacious vs a straight Iron Phosphate bait.
When we don’t really know and information changes from country to country, I favor being extremely cautious.
We find the “cheap beer in a cat food can” works very well to remove the offending slugs. A morning stroll in the garden with a plastic baggie covered hand, ready to pick up the munchers and plop them into a garbage bag helps too. No chemicals needed. 🙂
Thanks, as always, for your thoughtful ideas.
Excellent idea, and cat food cans are in good supply around here, as my daughter and I each have an aging female kitty (in two years, they’ve moved to wary detante). Onward!
I have resorted to Sluggo (and, of course NOT Sluggo Plus) because the natural control methods never seemed to do the trick. I’d lose whole youngish lupines in one or two days. Copper is also expensive if used in the garden (not just around pots) and I’ve seen reports that it doesn’t discourage all the snails, although it probably diminishes the number who make it their prize. I’ve tried crushed eggshells and of course beer… etc.
I also wonder if the natural methods work that well for you. You say, “I used to pay my kids a penny a slug and they easily made a dollar before breakfast each morning.” Hmmm. … For how long did that go on?
My biggest concern with Sluggo concerns the impact the birds. I don’t need to worry about dogs or cats, and I feel I have loads of earthworms in my soil, so that is of lower concern.
Although I’ve never had success with beer, I may give the enclosed plastic containers with holes a try, as suggested by one of your readers. However, I’m not expecting much.
My kids caught hundreds of slugs back in the day, but soon aged out of that. I switched back to beer because it’s cheap and quite effective in my last few gardens, which have been smaller and more easily managed. The downside is having to clean the traps each day, but again in smaller spaces, that’s not too hard. I’ve also started using a bit of fresh sourdough starter in traps, and that seems to be pretty effective as well. Thick, sticky and rapidly fermenting, what’s not to love?
My Beagle (dog) was rooting around outside one night and came back with the worst FACIAL of slugs I had ever seen. It was such a turn-off, I started to use Sluggo again. Sluggo turns white and gooey after rain or watering, so it isn’t all that effective to stop slug facials on my purebred Beagle 🙁
Can someone please come up with a cruelty free method of keeping slugs out of plants. One that doesn’t hurt or kill them please? They are living creatures that were here long before we were and are beneficial to the environment whereas humans are harmful to it.
Great idea, and I also wish that, but as far as I know, the only effective detterents are probably very painful for slugs and snails, which are indeed sensitive to pain. My own solution is not to grow plants that are especially susceptible to damage, so I mainly plant blue, crinkled hostas rather than delicious golden ones, and start lilies in pots, then transplant them once the shoots are large enough to outgrow nibbling. Also, growing extras of tender lettuces so you can replace any lost to molusc hunger. You can pick up snails that find the edible beds and place them in other parts of the garden where they won’t do any particular harm, but I admit that slugs are more difficult to spot and relocate.
Thank you for the research!
I was considering trying Sluggo again, after finding a new squash plant nibbled down to a nub today.
I use the “search at night with a flashlight/relocate” method for my own garden. I also have plants in a community garden a few hundred feet down the lane, but don’t want to disturb the neighbor’s dog, thus the thought of using Sluggo.
I decided to check about toxicity before ordering it, and I’m so glad I came across your article. Back to other methods.
That’s a great point
My problem is earwigs. I’ve tried everything and they are voracious eaters and reproduce quickly. I’ve looked at Sluggo Plus with a longing eye, but it seems like a bad option after reading through the comments. I’ve used peppermint spray on the earwigs but it doesn’t seem to deter them. Any advice?
Yes, earwigs can be tricky to get rid of. I’ve had the most success with light traps, which also work well for tent caterpillar moths. Here’s a good list of natural deterrents to try;
In researching plants that deter slugs as well as slug poisons, I came across your article. In the past, I had roughly crushed egg shells to sprinkle around the base of my plants. While slugs love calcium, the larger sharp pieces seemed to do a good job at keeping them away, but I have to continually keep up on it, and with egg prices I don’t go through as many as I once did, roughly 10 dozen each month previously. I have yet to try beer traps but will start initiating those within the next few days as well as growing plants that will help keep them out of my garden.