He's started just three times for Argyle this season and come off the bench four times. He's scored once.
Plymouth head coach Paul Mariner said: "Ashley has got a lot of attributes that you want.
"He is mobile and aggressive, but, like all young players, he needs to work on his awareness and his first touch - you could say that about every player walking.
"He is at a stage where it is probably a good idea for him to go out and hopefully be a star down there. He's played in our first team and scored this season, so he's coming along."