ETDA( ethylenediaminetetraacetate ) is a chelating agent That is widely used in fertilizers as well as snail baits. Its purpose is to aid in the break down of ferric compounds in to ions. Iron is a micronutrient for plants and is poison for slugs and snails. Low probability that you used enough of either Ferric Sodium EDTA or Ferric Phosphate EDTA to harm plants. Ferric Phosphate has been documented as killing dogs.

Question? It is bait that attracts slugs, they come to it and it it. Why should you use more than is needed? It is also expensive.

No, it's cheap. A 2# box of Corry's is about $8.

Why do I want to use more than they say is needed? Because, as I said, if you distribute half a teaspoon of pellets across a yard of soil, a snail will almost never encounter one. This was my experience with bok choy. I sprinkled the stuff as directed, and my plants eventually got demolished. Maybe I killed one snail. The rest waltzed right in. They're supposed to be bait, but I guess the snails liked the bok choy better. I want to sprinkle a barrier. Maybe half a teaspoon around each plant. That's about four times denser spread than they call for.

I guess what I don't understand is that if EDTA grabs iron, is that iron going to be unavailable to plants?