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?

20 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.

  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?

  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.

  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”

  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.

  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.

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