Kaka was dangerous throughout the game and was hard to contain with ball in hand but it was a disappointing outing for the Magpies who have now lost four from five this year.
When wing Tim Cornforth scored in the 69th minute Southland's four points were locked up and despite Hawkes Bay's best endeavours they struggled to find a way back in to the game.
Replacement flanker Dion Bates also crossed in the 75th minute, which gave the home side a rare bonus point.
Southland halfback Jimmy Cowan, who was playing his 100th game for the province, enjoyed a busy afternoon and capped a solid outing with a try-saving tackle to deny Hawkes Bay No 8 Mike Coman in the final play of the game.
Southland's victory also leaves Harbour as the only team who are yet to have won a game this season.
Hawkes Bay host Bay of Plenty in Napier on Friday in what looms as a must-win game for both sides as they look to avoid relegation, while Southland travel to Harbour on Saturday.
Southland 35 (Jamie Mackintosh, Jason Rutledge, Tim Cornforth, Dion Bates tries; Scott Eade 3 pen, con, Marty McKenzie 2 con) Hawkes Bay 7 (Adrian Barone try; Dan Waenga con) HT: 9-7