Originally Posted by ecoguy
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.)
My numbers were based on Fiesta concentrate. I did not look up mixing directions because as I discovered, the concentrate itself is not particularly harmful. So just multiply those numbers by 25 for the final mixed product (i.e. it would take 25x as much to cause damage).
Also, from the sounds of the response, they're using EDTA, not necessarily NTA as the chelating agent. Off the top of my head, EDTA is much less toxic than NTA, and with NTA being the worst component, it sounds like it is actually far safer than I assumed.
So yeah "your customer is full of crap". But at least you now have an official response from the manufacturer so you can break it to them lightly.