I call fake.
Although I didn't play around with it yet in photoshop, I don't think that very banana-like stem is in the original photo. I can see where the body of the banana might come from, but not the stem. Also, I can't see where the highlight along the body of the banana would come from either. To me, it looks like sanddrag superimposed a slightly translucent banana on top of an already (mostly) yellow backround, and matched it up nicely with the existing "banana-like" curves and lines in the photo.
Nice try, though.