Upon Further Review…Iron Phosphate for Slugs and Snails

I’m not going to sugar coat it – I’ve been too cavalier in recommending iron phosphate for slugs and snails. 

A few days ago Erin Harris put a comment in my post about dandelions asking whether those iron phosphate baits you can buy for slugs might also be toxic to earthworms.  The answer is yes – they might.  And not only that, these iron phosphate baits can also be toxic to other animals such as dogs.

How bad might these products be for dogs and earthworms you ask?  I don’t think anyone knows exactly, but to my knowledge this is the most recent paper on the subject.  And here’s an abstract on dog poisonings.

Now, based on the data I’ve seen on poisoning incidents, iron phosphate is less likely to poison your dog than its closest competitor, metaldehyde (though the iron phosphate seems more likely to hurt earthworms than the metaldehyde).  I’m not going to stop recommending iron phosphate – Still, I can’t recommend it quite as freely as I have been in my talks — I need to add some real caveats. 

So then the question is, how did I not know about the potential problems of iron phosphate?  Simple.  I assumed that the compounds listed on the active ingredient list were really the only ingredients I needed to think about.  Silly me.  Just like Round-up, and almost any other pesticide you can name, there are other ingredients that help the active ingredients work — and that could cause issues.  For Round-up, the soaps mixed in there to help the product stick can hurt frogs or other amphibians.  For Iron phosphate, the extra ingredient that could do some damage is EDTA.

So, you’re asking, what is EDTA?  EDTA is a chemical which makes metals more soluble, called a chelate.  In iron phosphate products EDTA helps the iron to be taken up into the body of the snail or slug making it work much better than it might otherwise.  EDTA is also used in fertilizers so that elements (usually iron) are taken up more readily (because they’re soluble).  But because EDTA makes metals more soluble, it also helps them get to places they shouldn’t go – like into an earthworms body.

Now don’t go thinking EDTA is bad.  It’s not.  In fact, if you ever ingest lead or some other metal you’ll be thankful for EDTA because it is used to help clear potentially toxic metals from the body.  EDTA is even present in some of our foods for various reasons.  That said, as with any chemical (including water!), it is possible for EDTA to do things we don’t want it to do in the wrong circumstances.   And that’s why we need to be more careful with its use.

As I said before, I’m still OK with iron phosphate products, especially as they compare to metaldehyde products, but you can bet I’ll be spending more time stressing its drawbacks.  I’ll also be spending more time touting beer.

For slugs of course!

Now, a question for you.  These iron phosphate products are currently listed by the OMRI (Organic Materials Review Institute) and some labels list it as being safe to use around pets and wildlife.  If the products include EDTA, should that be the case?  (You can look up EDTA in Wikipedia if you want to see how it’s made.)  Are you comfortable with using EDTA in organic production?  Does it matter to you if it’s used as a fertilizer vs. as an ingredient in a pesticide?

49 thoughts on “Upon Further Review…Iron Phosphate for Slugs and Snails”

  1. Interesting. Does anyone know the quantity of iron phosphate bait consumed that caused the dog problems? In the abstract it said “large amounts”.

  2. Knowing the amounts would allow for a better understanding of the risks. The Sluggo label rate is one teaspoon per square yard, dispersed evenly, which is pretty light. I wonder if the applied product presents a toxic dosage likelihood. I certainly appreciate this cautionary information, particularly about a product that is typically spoken of in such “safe” ways.

  3. There is a Material Safety Data Sheet.
    (MSDS) page on EDTA. I don’t know how to link to it. Google ~ MSDS EDTA ~ will take you to a clickable pdf link.

  4. Frankly, I don’t trust Wikipedia on something like this. The editors have an agenda. The entry for permethrin, for example emphasizes its toxicity to cats. That’s as useful a piece of information as an entry on chocolate emphasizing its toxicity to dogs.

    1. “The editors” are the general public. That includes you. As long as you have a reliable source to cite, you can edit any article yourself. If you put in crap, somebody will come along quickly and remove it. If spreading information is “an agenda” then they have an agenda. That’s the point of an encyclopedia.

  5. Thanks for the great post Jeff. I assume this caveat goes for the FeHEDTA product for dandelion control too? Or would it be ok because it doesn’t have a bait component?Perhaps encouraging people to spot treat instead of broadcast would be a compromise for dandelions. I definitely won’t be using it in my garden anymore. This may be a silly question but is there any brand of beer slugs prefer? Mine don’t seem to like Michelob (Ha Ha). Perhaps a different concentration would work better? If it is the yeast they are attracted to I could just do yeast water? Would they just crawl back out? Has anyone made a study of trying different things to see what works best?

    1. Dandelions are a symptom of a calcium deficiency in the soil. I farmed hundreds of acres and applied feed grade calcium carbonate 80% of which goes through 200 mesh at a rate of 200# of actual calcium per acre. The first year you will see a diminishing and by the second year if the calcium rate is sufficient for the soil, the dandelion seeds will be there but not germinate. These wonderful plants are telling us something we really need to understand. If the nutrients are not in the soil they can’t be in our food.

      1. Dandelions will grow in any level of calcium. They aren’t an indicator of nutrient deficiency. The only sure way to know if you need calcium or any other plant nutrient is to do a soil test.

      2. The dandelions grow just fine in Texas caliche. I’ve never see a study that would indicate calcium inhibits dandelions.

    2. I’ve tried sluggo with no luck. Coffee grounds around and directly in the stalks of the hostas doesn’t work either. Neither does ground egg shells or epsom salts. I shouldn’t say it doesn’t work…maybe it deterred quite a few but there were about 100 i picked off of my plants and tossed in salt water. I know that kills em.

  6. Erin,

    The FeHEDTA for dandelion control isn’t likely to be attractive to the dogs so it’s much less likely to cause problems. In terms of the beer that slugs prefer, I’ve heard of one group that did a study and found that they prefer darker beer — and another group that found they prefer lighter beer — I guess it just depends on how sophisticated your slugs are!

  7. Oops… I meant caveat for the earthworms. I’ll take it to mean the FeHEDTA would not be attractive to earthworms. I was assuming if it was broadcast onto the lawn it would be difficult for a dog to find a significant amount to eat anyway. Thanks!

  8. I do know of a case where some chickens died from eating Sluggo, but it was because they found the open bag and gorged themselves on it, sadly. I doubt that chickens would manage to overdose on Sluggo if it has been lightly sprinkled on a garden as directed.

  9. I have been using aniron phosphate product for strawberries and hostas. Last winter mice ate the box and bait in storage. Haven’t noticed a decrease in mice — but don’t usually get a chance to count them.

    1. I bought a bottle of slug go, put out a little,and saw squirrels trying to eat it. I think they or the raccoons would have chewed up the plastic bottle if I’d left it outside. I wondered about birds eating it. So I took old beer bottles and put the slug go in them, on their sides. I have seen the slugs go in to eat, but I don’t think even a mouse could get in there. I keep five bottles near my beans and peppers and maybe a half teaspoon in each. This doesn’t get to the earthworms either, except by the decomposing slug I guess. I do not have outdoor pets or kids. I am ok with the risk of this. I would use slug bait stations but when I put beer in those? The raccoons drank the beer. Hilarious. I wish they made ceramic heavy raccoon proof slug stations but honestly, I doubt anything is raccoon proof.

      Anyone want to get rich by making a slug bait station for people with raccoons?? I’ll buy!!

  10. The adage: pick your poison comes to mind. Using new products as badly as we’ve used the old products is only likely to keep creating the same problems.

    Slugs have areas where they live, then go out to feed. Putting baits near plants you want to protect only draws them to where you don’t want them. Confine baits to areas likely harbor slugs, such as among groundcovers, along the lawn edges, wood piles and such.

    What effect does beer have on pets? The effects on humans symptoms similar to some pesticides, yet we imbibe it freely.

    Lastly, I did test the dregs of Henry Winehard and Generic beer, (two catfood cans of each). Sadly, slugs have expensive taste – they did like Henry’s better.

  11. Hand warmers and toe warmers too say on the packet that they are just iron phosphates. Can you take the contents of these packets, when their ability to produce heat is over, and sprinkle them where the slugs “hang out”

    1. No. Slugs have no reason to munch on that. You need to mix it with their favorite foods, at the right dosage, to see any positive effect — other than serving as a general fertilizer.

  12. Questions were asked about the level of toxicity of iron to dogs, etc. Or in cereal, etc. Humans have the ability to metabolize small amounts of iron; to expel what they don’t use. Dogs do not have this ability. The Iron continues to build up in their system over time so they may consume just a little each day, but it stays in their system. Obviously small dogs will be impacted sooner than large dogs. Here is an unvalidated information link from 2010 you may find helpful: http://www.hostalibrary.org/firstlook/RRIronPhosphate.htm

  13. For the record, I have determined that SLUGGO brand snail and slug bait does not contain EDTA. Some other, newer, baits, such as Ferroxx or Slugexx do. I will continue to use SLUGGO, sprinkled thinly, and only as an occasional backup for handpicking and habitat management.

    1. Cheap beer kills my slugs but not my snails, I think this is because the traps I laid were too shallow and the snails were able to climb out, while the slugs gorged themselves and drowned presumably in a blissful drunken stupor. Or it could be that slugs don’t mind cheap beer, and snails have more sophisticated tastes. I am now using a deeper beer trap and plopping snails in there when I spot them. There is also the option to only grow flowers that these slimy creatures do not find attractive to eat, and then the need for war with them is over. For example, they don’t want my rocket and the spicier of the salads, or pelagoniums, geraniums, herbs and aquiligia, which can be planted low down, while my tender seedlings and pots of mild lettuce are protected on a high shelf.

    2. Pam,

      Your comment is two years old so you may not see this, but how exactly did you determine Slugglo does not contain EDTA?

  14. If I had a choice, I’d give up worms to be rid of slugs also. I’d rather have neither, than both! Like it or not, while worms are helpful in compost, I think most people give the worms to much credit for making compost. Most of the work is done by beneficial bacteria, fungi, etc.

  15. I live in an area that teems with a variety of birds that visit regularly, as well as magpies, blackbirds, and larks which visit every day – or rather, they were until recently. One day I got fed up and felt like I was losing the battle with the slugs and snails (picking them up by hand and bagging them – anything from 100 to 500 at a time of the munching mongrels – or stomping on them) so I bought the iron phosphate type slug and snail pellets which are marketed as safe for cats, dogs, children, lizards, frogs, BIRDS, and earth worms etc. Within a few days I began to notice a large drop in the number of birds around my immediate area. About 5 days after laying the pellets the bird life had dropped to 3 magpies (out of 2 dozen usual visitors) and one blackbird(out of the usual 6 or so).
    Yesterday, there were no blackbirds to be seen or heard and only one magpie which was sitting quietly and forlornly. He looked lonely and either sad or sick, so I tested his appetite with some bread, which he ate. I suspected the snail pellets for the rapid disappearance of birdlife so I have been going round the gardens picking up every little bit that I can see. I don’t know how long it will take before a normal population of birds, earthworms and wildlife will be restored to the area. I am very sad and very cross that manufacturers are marketing these pellets as safe to wildlife when clearly it is NOT SAFE!!

  16. That’s very interesting Janet. I don’t know much about the toxicity of these baits to birds. It is certainly possible that the baits are poisonous to birds, but I want to caution you that correlation does not necessarily indicate causation. I hope things turn around for your birds soon!

  17. I had a similar experience as Janet’s. My very busy and bird filled back yard in town was treated with a very light sprinkling of Sluggo on the bare soil in a flower bed, and the birds absolutely vanished for 4 days. That was 5 days ago. Today, a few sparrows came back to the feeder. One Junco came later. I have had a steady stream of birds all winter until this event. Flocks of goldfinches and pine siskins are gone. Towhees left as well as the song sparrows. The hanging feeder has not needed to be refilled.
    I wonder if the Sluggo has a noxious odor that only birds can smell that drives them out and away from their food source. It has not rained here to wash it away.
    Next time I will put the Sluggo just under my pots and under a piece of board, so birds cannot ingest it.

  18. I live in the Pacific Northwest and have used Sluggo in the past for my garden. This year, 2015, I have caught the birds eating the Sluggo. That can’t be good for them. I’ve never seen the birds do that before. Does anyone know anything about this? They are eating every spot of Sluggo I put in the garden…very worrisome.

    1. I’m in the PNW and concerned, also. I have noticed that when I put it out, it has mostly disappeared by the next day. Today I have twice witnessed a Junco taking a pellet of Sluggo from my garden and feed it to his fledgling! I’m trying to wash it away and will not be using it again… 🙁
      I never would have used Sluggo if I had known that birds would eat it. That makes it unsafe for organic gardening, IMO!

  19. I was assured by the manager of a exclusive chain of garden centres, that, ferric phosphates did no harm to garden birds, I hope he is correct. or I will have his guts for garters,
    signed : a trusting gardener.

  20. I haven’t read through all the posts above so don’t know if anyone has mentioned this already but the report the report being referenced is sponsored by Lonza who produce Meta, a Metaldehyde product sold to companies that produce Metaldehyde containing slug pellets. Being of a cynical mind one might question whether the research is entirely unbiased….

  21. Well thank you everyone for the informative comments, I was about to go to the shop to buy some organic slug palets but I will not. I Guess that when gowing organically we just have to accept some crop loss. I will consider it my duty stamp to nature from now on, a small price to pay for everything it gives us.

  22. has anyone tried a spray with neem oil? tobacco,? hot pepper? garlic? these all should be effective, and also distasteful though not poisonous to animals, except perhaps tobacco. (worms keep away!)

  23. A bit confusing, but it seems iron phosphate is not safe (it also contains EDTA to make it effective- but not mentioned by the manufacturer…)
    Surely all those home remedies ARE the answer

    1. Home remedies are never the answer. They may help guide scientists towards experiments that can support the use of alternative materials, but they certainly don’t take the place of science.

  24. I did a research article on this in 2010, interviewing vets and vet toxicologists and looking at the online patent for Sluggo. Up until then, the company was publicly evasive to downright mendacious about the EDTA content, but as word got out swiftly in spring of 2010, the company sent a rep to come clean on the EDTA to the organic standards board. The extreme toxicity of metaldehyde has long been documented. Toxic dosage to some extent depends upon pounds of dog, and for most dogs access to the container would be required for a lethal dose. But there had as of 2010 been plenty of documented illnesses, and it was clear that the product was not a health food, as the PR had virtually suggested.
    I sent my article to a major magazine with a section on gardening; I sent them links to the patent, etc.- which they refused to read, and insisted that obviously I was lying about the EDTA. The article is still online; I have not kept up with stats on poisoning or further developments with the product’s image problem. I use it- carefully. I have found that a very tiny amount works. But I have seen people who owned dogs piling pounds of Sluggo around every plant, as if mulching.

  25. Hello from New Zealand! I recently used iron EDTA to check the impact of slugs on seedlings, It may have had an impact on the Slugs, However, after 8-10 days I did notice that some of those iron edta baits got covered in Fungus. So now we have bits of fungus around the potted plants. Is there any solution for this or workaround to avoid fungus covered baits?

  26. I wish someone would invent a “trap” where you put the bait that makes it less accessible to pets! Doesn’t that make sense?

Leave a Reply to Olen Cancel reply