[Plantoid]

Ammonium sulfamate aka Ammonium sulphamate ( not to be comfused with ammonium sulphate ) is apparently one of the very few effective chemicals that kills it ( horsetail ) off but at the cost of having to leave the ground uncultivated for a couple of months.
 It is easily available and reasonably cheap in the UK and as it decays it leaves nitrogen as a fertilizer in the ground.

It is not sold as a weed killer because it is not licenced for such purposes because of the Irish EA's  request for it to be dog friendly tested but it is sold as a compost maker instead and does not need a licence for this purpose.

 Google the words and there is quite a decent blurb about it. It appears to be good for erradicating several other persistant weeds including japanese knot weed

I found out about this on another site I occasionally frequent there are several agri chemists and agri contractor businesss people on the site .. its been an interesting time reading about it all.

[SallyintNorth]

It was amicide the nice ladies at the HDRA told me to use if I really really had to use chemicals - I think I rememnber that an example was to kill off a tree stump that couldn't be dug out.  But to be careful it couldn't leach into a water course.

[Plantoid]

Yep thats a trade name me thinks ..the names I've given are the chemical name , are available on ebay and via the net so should  be cheaper even with delivery..

[harry]

got some yesterday waiting for rain to stop to use it

[Rosemary]

Will animals graze horsetail? We have it in one paddock that hasn't been grazed but not in another (right beside it) that has sheep in it?

Do you need to exclude livestock if you are using amicide?

[harry]

if they do graze it it comes back double