Interesting that some folks find crushing the stems help, technically it shouldn't.
You have to remember that it is a Xerophyte or conifer which, as with all conifers, has evolved to cope with the the lack of available water in frozen areas of the planet.
The needles , like all conifers, have the stomata on the inside of the 'leaf'....if you were to cut a cross section of a leaf or needle and magnify the section you would find it is horse shoe shaped with the stomata around the inside of the 'horshorse' - this makes herbicide entry very difficult.
Further more it has silicon deposits around the Guard cells that protect the Stomata which have been called by weed researchers rather colourfully 'Iron gates'.
The physiolgy of the weed is such that damaging the stems will not increase translocation. This has been demonstrated by researchers adding isotope tracer to to herbicide sprays and growing it in tall glass troughs, you can then image how far down the stem the herbicide actually goes and its not far!
Products that contain Glufoinate-Ammonium such as Finale or Kurtail seem to work quite well but this active ingredient has a contact or translamminar mode of activity rather than relying on translocation like Glyphosate for example.
I always think there is confusion between Horsetails & Mare's tail (I often mix up the names..). I suspect we are all really talking about Horsetails as real Mare's tail is an Aquatic based weed ?
If so, the issue of bruising or crushing stems comes about from direct product instructions from Monsanto when dealing with it using Roundup and therefore all (?) similar based products.
Use a Biactive formulation of Roundup with its superior wetters and consider adding up to 2% Mixture B NF or Ethoxylated Tallow Amine wetter.
Wait until the vegetative shoots have reached maximum height (60cm), usually July.
Bruise the stems lightly immediately before treatment. This will break the waxy layer and allow much better penetration of the glyphosate. To achieve this small areas can be brushed with a stiff broom, field areas are best with a Cambridge roller. The bruising must not be severe enough to break off the stems.
Apply the highest rate of Roundup Pro Biactive recommended."
We have site infested with the dammed plant (even piercing mylex) and this approach seems to have worked without using expensive products.