If you are killing and clearing a large area of horsetail, use this concentrated weed killer, rather than the sprays. Instructions for best way to apply liquid Glyphosate weed killer to the waxy stem and leaves in the article above.
To purchase Concentrated (360g/l) glyphosate weed killer click on the amazon picture
for more product info. Visit the shop for weedliller
Symptoms of Horsetail poisoning in Horses are: