Like most things in life there's no simple answer. While I agree with Lou about the turn being "built in" for most aircraft there are always exceptions. Pattern and hardcore aerobatic sport models or the hot pylon racers mentioned above that are trimed to dead on neutral stability do not have even the most basic decalage or longitudinal dihedral (as in up trim) to produce the basic turn once banked. Without that built in pitch stability or application of up elevator the model will side slip right into the ground. But in reality that is a very special case that applies to a very small percentage of aircraft be they models or full sized. For the rest there's enough built in decalage to provide at least a minimum of the up elevator trim to "climb" around the turn even if that turn is a spiral dive.

I say there's no one single control that turns the plane. The aileron or rudder plus dihedral is neccesary to bank the craft and then the positive pitch stability or elevator input is used to make the airplane pitch up around the turn. So it takes TWO controls or factors to provide even a basic spiral dive type turn.