If a wild ditto is battled and killed, will its EV yield be that of the Pokemon it was transformed into, or will it be 1 HP no matter what?
Ditto gives off 1 HP EV, but when he transforms, he still keeps his own yield, meaning he still gives off the same one HP EV when he is transformed into another Pokemon.
Simple as that! ~(.^_^.)~
SOURCE: Personal experience and a conformation with bulbapedia!
After ditto transforms it will give the EV yield of the Pokemon it has transformed into rather than its own 1 hp EV