Evans added to Dean Kelly’s first-half lead within a minute of coming on in the 71st minute, side-footing home Kelly’s cross from the right for his third goal of the season.
A solid start, in which David O’Sullivan and Pat Sullivan had openings, counted for nothing for Longford were to be punished at the game’s first corner on 23 minutes.
Lorcan Fitzgerald’s delivery picked out the unmarked Kelly and the Bohs striker scored with a simple downward header.
Longford lost midfielder Stephen Rice eight minutes before half-time
. Initially injured in a collision with Roberto Lopes in the ninth minute, Rice played on after treatment.
But he was replaced on 37 minutes, put on a stretcher and taken to hospital.
A patchy second half didn’t come alive until the 69th minute when Dean Delany saved O’Sullivan’s shot.
Delany; Pender, Lopes, A. Murphy, Fitzgerald; Kavanagh, Dillon, Creevy, Moore (Evans, 71); Buckley (O‘Brien, 79); Kelly (Griffin, 87).
Hunt; Mulhall, Sullivan, Tyrell, Powell; Ben Mohamed, Rice (Salmon, 37), Gorman, O’Connor (Simon, 57); O’Sullivan, Shaw.
Sean Grant (Wexford).