Highlanders first five eighth Hayden Parker scored 20 points in Taieri's big win over Green Island in the derby, and Highlanders winger Ryan Tongia scored a brace of tries as Southern won the battle of the beach.
Dunedin is the third unbeaten team, but has not yet claimed a four try bonus point.
Two rounds, on Thursday and Monday, will be played over Easter.
Dunedin 15
Zingari Richmond 5
In a match which failed to reach any great heights, Dunedin did enough to beat Zingari Richmond at Montecillo.
Dunedin led 15 5 at halftime and no points were scored in the second half, despite both sides having chances.
Zingari, especially, was plagued by errors at just the wrong time and its ball security was not good enough to challenge.
Dunedin started with a rush and had 10 points on the board in as many minutes. Greg Dyer kicked a penalty and No 8 Gareth Evans _ on loan from the Highlanders _ came off the back of a scrum and crashed over from 5m out.
Zingari made too many sloppy errors and was not helped by two men, Tom Rowe and Steve Roberts, spending time in the bin.
The home team's kicking lacked accuracy while Dunedin rather fumbled its way through the second half. Home captain Joe Latta lost the ball in the act of scoring in the second half.
Best for Dunedin were second five eighth Callum Bruce and Evans, while hooker Sam Anderson Heather made some strong runs before leaving the field early in the second half.
Lachie Moore looked dangerous with the ball for Zingari while Latta and Blair Tweed got through plenty of work up front.
Southern 31
Pirates 3
Southern got the bonus point and the win in a messy match against Pirates at Bathgate Park.
The home team could have expected to win easily but made hard work of it at times, in a game that did not have a lot of flow in it.
There was plenty of vigour from the Pirates forwards, who threw in the towel, especially around the breakdown.
Highlanders winger Ryan Tongia scored two tries for Southern _ giving him five in two matches _ and his second one, where he split the defence up the middle, got his side the bonus point near the end of the game. Tongia had scored the first try of the game and Southern led 17 0 at the break.
Adam Knight got through plenty of work in the Southern pack, and front rowers Warren Moffat and Cameron Keach were energetic.
Pirates props Craig Millar and Hisa Sasagi worked hard and got round the field and Josh Clark was tigerish in the loose.
Alhambra Union 48
Kaikorai 13
The home team made no race of it at the North Ground with a convincing win over Kaikorai.
Kaikorai was looking to bounce back after a disappointing effort last week but it never looked likely and was down 22 3 at the break.
Alhambra Union worked hard in the rucks to get the ball to its backs and Highlander Kurt Baker, playing in the No 10 jersey, found plenty of holes for himself and those outside him.
Noah Cooper ran well at fullback and Alhambra Union was too wise for a young Kaikorai side.
Caleb Gray fed his backs well from halfback, and Tom Frood and Ben Tuiomanufili worked hard up front. Locks Mike Colville and Sean Boult got through plenty of work.
The scrums were relatively even but the home team won the breakdown battle and that helped its expansive game.
Kaikorai hooker Lachlan Landels and halfback Josh Renton tried hard but the side needs some experienced players back to try to find some form and confidence.
Taieri 65
Green Island 7
The skill of first five eighth Hayden Parker was the catalyst for Taieri's 11 try romp over Green Island at Miller Park.
Parker broke through the stubborn Green Island defence with a jinky 18m angled run to the line for the second Taieri try. He scored 20 points with two tries and five conversions.
The floodgates opened after Parker's try, as the Taieri backs and forwards attacked from all parts of the paddock with precision support play and slick passing.
Parker's second try, midway through the second spell, was the best of the game. It started behind the Taieri goal line and the ball went through 10 pairs of hands.
Winger Glen Beadle took every opportunity and used his speed and anticipation to score three tries.
Other Taieri backs to impress were halfback Will Cosgriff and midfield back Michael Collins. The best Taieri forwards were No 8 Charlie O'Connell and flanker Willis Scott.
The best Green Island players were lock Jamie Waller and hard tackling centre Tino Elisara.
Harbour 24
University A 13
A 30m break by Seko T Pole in the 12th minute and deft finishing touches by Aleki Morris set Harbour up for its win over University A at Watson Park .
T Pole's run exposed weaknesses in University A's defence, leading to Morris receiving the ball and breaking through three defenders for an elusive 20m run to score under the crossbar.
From that moment, despite having plenty of ball, University A was kept on the back foot by a committed Harbour defensive pattern. This paved the way for two further tries to the home side for a 24 10 lead at the break.
Harbour's only blip in an otherwise faultless defensive effort came on the stroke of halftime, when University A halfback Kaide Whiting exploited space around the fringes to score near the posts.
An intense battle ensued throughout the second half, but the only scoring came minutes after the restart, through a Stephen Fenemor penalty.
Harbour was well served by its loose forward trio, and Morris and Logan Allen featured prominently in the backs.
For University A, Whiting cleared the ball well at halfback behind a pack that was beaten despite a high workload put in by David Simpson and Ed Elvin.