It was only the second goal this season from the Gortnahoe native.
Following that 1-0 win the Saints will welcome Arsenal to St. Mary's in the next round.
Meanwhile a first goal in seven years for Lucas gave Liverpool a 1-nil win over Plymouth in their replay at Home Park.
Liverpool will take on Wolves at Anfield in round 4
Matt Ritchie struck twice for Newcastle, who claimed a first FA Cup win in 5-years.
Rafa Benitez's side were 3-1 winners at home to Birmingham, and will be away to Oxford in the next round.
