A useful word, albeit specialist, being principally of interest to arboriculturists. Many have no doubt undertaken the task this word identifies, though it is certain that almost none among them have thought to apply the term to the chore. This is an exception:
The most infallible art of emuscation, is taking away the cause, (which is superfluous moisture in clayey and spewing grounds) by dressing with lime.
Sylva: A Discourse of Forest Trees & the Propagation of Timber, by John Evelyn, 1664.
Mr Evelyn precedes these sage remarks by a description of various methods of emuscation, which will serve to explain it:
Moss, (which is an adnascent plant) is to be rubb’d and scrap’d off with some fit instrument of wood, which may not excorticate the tree, or with a piece of hair-cloth after a sobbing rain; or by setting it on fire with a wisp of straw, about the end of December, if the season be dry, as they practise it in Staffordshire.
Sylva, ibid. Sobbing here is not from our usual sob but from another of unknown origin that means “soaking, saturated”, which seems to be unconnected with sopping.
So, emuscation means to remove moss from the bark of a tree. Its source is Latin muscus, moss, preceded by e, meaning “out”.
A plain English equivalent would be de-moss, but Evelyn was never one for the brief and homely term when a Latinate extravagancy was possible. In the second quotation above he has adnascent, meaning something that grows upon something else, and excorticate, remove the bark from a tree. Elsewhere in the same work — among many other examples — are ablaqueation, removal or loosening of soil around the roots of a tree or vine; decubation, the act of lying down; introsume, to take internally or absorb nourishment; perflatile, exposed to the wind or well ventilated; and stercoration, the action of manuring with dung.