. . . "(B) reimbursement of 50 percent of the cost of pruning, removal, and other costs incurred by an eligible orchardist or nursery tree grower to salvage existing trees or, in the case of tree mortality, to prepare the land to replant trees as a result of damage or tree mortality due to a natural disaster, as determined by the Secretary, in excess of 15 percent damage or mortality (adjusted for normal" .