Sapping

She kept hurtful weeds from growing beneath her trees and sapping the earth-food required by her charges.

There have been many reports about the 'brain drain' sapping the intellectual strength of developing countries by drawing the best and the brightest to higher paying jobs abroad.

December 22, 1821, Joseph Story, Address Delivered Before the Members of the New-England Society, in Charleston [The government] may be destroyed by popular violence, or the madness of party, or the deeper sappings of corruption.

And when he had me up there he would sap me again and I wouldn't remember anything that happened in between the two sappings.