"Hi All, I Have completetly ridded myself of Mares tail and am now 2 years free. Amonium Sulphamate crystals are what you need. Dilute in water and spray on, wait 2 weeks then go again. The ones sprayed wont be seen again and the ryzomes will be heavily weakened. Keep an eye out the following spring - they will be back but barely, then repeat".
We have horsetail in our garden as well. I tried spraying the stalks with "Simple Green All-Purpose cleaner and it seems to be killing it. The stems turn brown and die. Not sure why it seems to work and would like someone with scientific knowledge to tell me if I am correct, and if I risk killing other plants near by when I spray.Kimmer