Hey all. Just received this official response from the Neudorff, the Fiesta Manufacturer.
It’s unfortunate that this customer lost his fish; however, it is very unlikely that it was related to the Fiesta application. In this scenario Fiesta wouldn’t have reached the pond, and even if it did, FeHEDTA is not toxic to fish.
1. Fiesta is diluted 1 in 25 prior to use, which means that the bulk of the end-use product is water.
2. Fiesta was applied 5-6 feet from the pond. Nearly all of the FeHEDTA applied is immediately absorbed by the grass and weeds and doesn’t reach the soil layer. The FeHEDTA is then degraded by light and/or metabolized by the grass within a day or two. It has a very low potential for leaching (does not travel through soil to runoff into water.)
3. Even if it did somehow reach the water, FeHEDTA is soluble in water and is rapidly degraded by natural light.
4. The regulatory authorities do consider the potential impact to fish and aquatic organisms when evaluating a pesticide. I’ll attached the Canada and US evaluations.
From the Canada PRD: “FeHEDTA is expected to pose negligible risk to terrestrial and aquatic organisms under conditions of use for application to turf.” The toxicological studies found no toxicity at the highest concentration tested for fish (rainbow trout) and aquatic invertebrates (Daphnia).
From the EPA BRAD: “Studies indicate that iron HEDTA will not cause adverse effects to mammals, birds, fish and aquatic invertebrates, other non-target insects, or plants.” The toxicological studies concluded that iron HEDTA is “practically non-toxic”, which is the safest EPA level of classification, to fish or aquatic invertebrates.
Let me know if you have any more questions.