Some trainers may be familiar with EV training already, but what if you wanted to train a pokemon from scratch and you wanted to reset the EVs? With the help of EV reducing berries this becomes possible and it saves time so you don't have to go around looking for the right pokemon.
Each Berry reduces its respective EV value(Check the description)by 10 EVs. So its basically the opposite of proteins, calcium, etc. The first berry of use will reduce the number of EVs to a max of 100(if it was above 100 to start with). If it was below 100, then the berries reduce the EV points by 10. So you would essentially need 11 berries of a kind to fully reduce the EVs to zero. These berries also increase the happiness of your pokemon.
Here is a list of the EV reducing berries:
#21 Pomeg Berry (HP)
#22 Kelpsy Berry (Atk)
#23 Qualot Berry (Def)
#24 Hondew Berry (SpA)
#25 Grepa Berry (SpD)
#26 Tamato Berry (Spe)