Question
There is a single, long, rust colored mushroom coming out in my back yard. If touched powder falls off. Is it poisonous

Answer
Hi Trevor, Making an identification of a mushroom without seeing it is tough and the best I can do is make a guess.  From your description of it being long (I'm assuming no prominent cap) and rust colored that it may be Cordyceps militaris and it is not edible.
This is the correct time of the year for it.  Jim