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?
Bulbapedia says “ From Generation III onwards, Transform also copies the base experience, and the EV yield of the target.”
After ditto transforms it will give the EV yield of the Pokemon it has transformed into rather than its own 1 hp EV
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!