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Tuesday, March 1, 2022

Organic Solution to Slugs - Iron Phosphate

(Updated and re-printed from June 2012) The Monroe Sharing Gardens is located on ground that stays marshy well into the spring - even on a dry year. For the last few years since we've been here, we've had exceptionally wet springs so it can be downright boggy. Add to this the fact that some years we add - literally - tons of leaves, straw, grass and other kinds of organic matter and you've got the perfect environment for slugs to thrive. 
Slug eggs - if you find these in your garden, get rid of them (not in your compost pile!)
In 2011 we had a bad infestation--they decimated lettuce, kale, broccoli, peas -- all the cool-weather crops but even in the heat of summer they never died back and some tomato plants were basically just slug apartment dwellings; all you can eat buffets for the gastropods that make the Pacific NW famous. Buckets of potatoes were too slug-eaten to save and went straight to the compost. We knew that this year would be even worse as we came across underground deposits of hundreds of their small, pearly white eggs, just waiting for the perfect spring conditions for them to hatch.
We moved forward in good faith, figuring that somehow their numbers would balance out and they would join in the spirit of sharing that the gardens are famous for - a little for them, a lot for everyone else. But when we came to the gardens just a day after a team of four OSU students did a massive planting of literally hundreds of lettuce, spinach and broccoli and found two out of the four, seventy-foot rows practically disappeared overnight, we knew we had to find  a solution, and find it fast.

Whole rows of lettuce and broccoli, eaten overnight.
Chris went on-line and searched for organic solutions. We needed to find something that would get the slugs under control without endangering humans or our healthy earth-worm population, the snakes who feed on the slugs, the birds who frequent the gardens, or any other wildlife. There are a lot of folk-remedies out there such as coffee grounds, eggshells, citrus peels and beer-traps. All with only moderate success rates, or unpleasant side-effects (emptying beer traps with decomposing slugs is not a pleasant task!)

So, imagine our great joy when Chris discovered that iron phosphate, commercially know as "Sluggo", is a mineral naturally found in the soil and is non-toxic to humans, worms and other wildlife. The iron phosphate is coated with something that is appealing to slugs, and keeps the pellets from dissolving in the rain (it can last up to two weeks for each application. It's also very easy to use -- you just sprinkle a little at the base of each plant, or in the spaces between the plants. When the slugs eat it, it makes them lose their appetites, or binds up their digestion and they die within a few days of eating it. This also disrupts their reproductive cycle as the slugs aren't around long enough to mature and lay eggs so, theoretically, once we bring the population back into balance, we will need to use far less of the product (or none at all) in future years.

Healthy rows of lettuce.
We have been applying it now for about six weeks and are having fantastic results. In the beginning we had to reapply it every few days to keep up with all the slugs being hatched. Now, the applications are staying uneaten until the product naturally dissolves into the ground.

If you buy the product "retail" you can expect to pay $6.00 - $7.00 (or even more) per pound. So, if you need a lot, look for a wholesale sorce of iron phosphate with a coating. It will be less expensive than buying name-brand products such as Sluggo.

Kept in balance, slugs can be integrated into the garden's natural fauna.
Here is info from another organic farming site (Green Methods)attesting to the safety and effectiveness of Iron Phosphate:  
Iron phosphate (brand name Sluggo), is an organic slug and snail controlling compound that breaks down into fertilizer which has proven itself extremely safe and amazingly effective, even in the wettest of conditions where slugs and snails tend to be most problematic. In fact, based on the copious amounts of positive feedback we’ve gotten over the years, we can say with conviction that this product last longer, works better, and is much safer than the industry standard, highly toxic, metaldehyde. 
This product can be used just about anywhere, and up to the day of harvest on crops. To use it, towards evening simply scatter the plastic-like granules on the ground or in the pots/benches where slugs and snails are found feeding (even in wet conditions). Once they have eaten the bait, they’ll find cover and slowly die. And it is literally as simple as that.

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  1. Iron Phosphate is way better than the old pellets BUT it contains a toxin. (A compound in the "inert ingredients" mixes with the active ingredient). That is how it kills slugs and snails. It is irksome to me that they get into the fold with gardeners who think it's 100% organic. There are some university studies that indicate Iron Phosphate hurts other organisms. And there's Sluggo PLUS that also has spinosad - if you don't apply it according to the fine print instructions then it is highly TOXIC to BEES. Again, it is better than the old stuff but you might want to read into it.

    There is some info at slugshield.com (bottom of page).

  2. Sharing Gardens reply: We have not found any other solutions to the slug problem that are sufficient for the needs of a large-scale garden. There are other garden practices that also damage worms: tilling and digging take their toll as well (for example). That said, 1) We only use the basic formula with iron phosphate, which does not appear to be as toxic to worms as the trials quoted in the comment and 2) our gardens, with the deep-mulch method provide SO much great habitat (food and shelter) for the worms that our populations are very strong; and 3) Slugs are surface feeders. Worms feed mostly under-ground so they get very little exposure to the Sluggo pellets. (There are some forms of worms - Nightcrawlers- that come above ground and pull material into their holes. These types would be most likely to be effected by the application of Sluggo.) We apply Sluggo very judicially around the base of the plants, not randomly over the whole garden. Until we find a better alternative. We'll continue to use Sluggo.

  3. I've been using a vinegar spray with some success when it comes to the smaller slugs(Deroceras reticulatum) . Though, it only seems to annoy the banana slugs(Ariolimax columbianus), japanese slugs(Limax maximus) and the Black slug (Arion ater) unless it's nice and sunny out.. It will kill the babies and eggs and works on snails too. The night crawlers don't like it, but it doesn't seem to harm them..

    1. Thanks for your comment. Good to know. One thing we've noticed is that we have snails that don't seem interested in our veggie-starts. We guess they must be a native variety that only eats decomposing matter and isn't interested in living plants. This is true for Banana Slugs BTW. They are native to the Pacific NW and, if they find their way into your garden should not be systematically killed. They will help your composting without harming your plants.

  4. As far as I am aware Iron Phosphate 111 is an inorganic compound.

    1. "Organic" -- in the sense that it is approved/legal for use on organic farms.

  5. 2014 Update: After two years of consistent use of Iron Phosphate/Sluggo, we seem to have brought the slug population into balance. We use the pellets primarily in the spring when transplanting out our lettuce and brassica "starts". Here in the Pacific NW, conditions are very wet and cool at that time of year --perfect slug weather. The trick is to break their cycle of reproduction by eliminating the egg-laying grown-ups.


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