Ma’aser Sheini 5:7

Let’s say that nowadays (i.e., after the destruction of the Temple), one has produce that in Temple times would have been eaten in Jerusalem and the time for removal arrives; how is he to proceed? Beis Shammai say that the produce must be redeemed with money. Beis Hillel say that even if he did so, the money would then need to be removed! Therefore, the produce should simply be left to rot.

Ma’aser Sheini 5:8

Rabbi Yehuda says that they used to send messengers to alert people that the time for removal was approaching so that they could remove the various tithes and portions and distribute them to the appropriate recipients. When Rabbi Akiva came, he taught that produce that had not yet reached its tithing time need not be removed.