Dunedin also secured a bonus-point 43-35 victory against Zingari-Richmond.
Kaikorai consolidated its place in the top four with a crucial 25-17 win against Harbour, while Green Island and Taieri drew 15-15.
Dunedin: 43
Zingari-Richmond: 35
Both sides will want to hit the tackle bags a little harder this week.
Dunedin outscored Zingari-Richmond seven tries to five in its 43-35 win at Kettle Park.
It will keep the Challenge Shield for another two weeks and picked up five points.
That part would have been satisfying but the Sharks were not as clinical as they will need to be against better teams.
They started both halves strongly but faded and let Zingari back into the game.
Dunedin scored three tries in the opening 15 minutes. Tim Cossens went over for the first and almost had a second when he gathered in a chip kick and made a long, angled run towards the corner. Impressive winger Mone Samate-Palu finished off what was a sweeping 80m counterattack.
But Dunedin handed over possession and Zingari replied with a try to winger Zayden Tane and then a second to prop Chris Preddy.
Dunedin led 22-14 at the break but struck twice in the next 10 minutes. Zingari scored next to stay in the hunt but, when replacement halfback Angus Vincent scooped up the ball from a 5m scrum and dived over, the game was basically over.
Dunedin openside Jamie Mowat could not be faulted for his defensive effort, while loosie Ashley Craig linked well and made some good bursts.
For Zingari, centre Ciaran Gaffney carried strongly and first five-eighth Thomas Johnson drilled all five conversions.
Southern: 41
Alhambra-Union: 5
Southern continued its reign at the top of the table through a convincing 41-5 victory over a budding Alhambra-Union at Bathgate Park.
Playing an expansive running game, Southern took control through its big forward pack to dominate from the outset. Openside flanker Josh Clark and locks Andrew Sanders and Axel Hohneck maintained a high work rate to kept Alhambra-Union on the back foot.
With Southern controlling the opening exchanges, it was prop Craig Millar's charge through the Alhambra-Union defence that led to the first of his side's five tries when right wing Ben Leggett dived over in the corner.
His try announced the entry into the game of first five-eighth Josh Ioane, who landed the sideline conversion and went on to land seven from seven attempts at goal and score one of Southern's two second-half tries for a tally of 21 points.
Despite a high percentage of territory and possession, it was to the Broncos' credit that the home side was unable to cross into the end zone again until the final minutes of the first half. But these two for Southern were ones to savour and came as just reward for the support play of blindside flanker Kyle Harris and Sanders.
Up 27-0 at the break, Southern was slow to get going in the second half.
Its final two tries did not come until the 20th and 35th minutes, due to Alhambra-Union replacements Harley Iraia, Max Aitkenhead, Sione Latu and John Tapueluluheu lifting the side. Tapueluluheu proved a menace down the right flank and fullback Poasa Cama proved dangerous on the counterattack.
Green Island: 15
Taieri: 15
Green Island was a touchline conversion away from recording its first win for the season.
It trailed Taieri 15-3 at halftime at Miller Park but rallied with two second-half tries.
Replacement winger Shane McNoe scored right on fulltime, leaving the scores tied and first five-eighth Ben Patston with a difficult shot from the sideline to win the game.
Patston pulled it to the right of the posts but the draw broke a string of nine losses this season.
Taieri dominated the opening 40 minutes, the Eels scoring through loose forward Nick Henderson.
The visiting side had barged the ball up field and spun it wide for Henderson to score in the right-hand corner in the eighth minute.
Elusive centre Christian Kelly crossed following more pressure and Matt Whaanga banged over a penalty to make it 15-0.
But right at the end of the half, Green Island got on the scoreboard through a Patston penalty.
Green Island enjoyed long periods on attack in the second half but took 20 minutes before it could add to its tally.
Hooker Peter Mirrielees made a dab down the short side following a lineout drive and crashed over about 5m in from touch.
Patston drilled that conversion and his side continued to pile pressure on Taieri.
It battered away at the line in the final moments and McNoe eventually crossed in the corner to draw the game.
Second five-eighth Latu Siaki was arguably Green Island's best player, while openside Josh Brown had a fine game for Taieri.
Taieri halfback Ryan Hammer played his 50th game for the premier side.
Kaikorai: 25
Harbour: 17
A clinical Kaikorai XV dominated the first spell, but Harbour came back strongly and ruffled its feathers after the break.
Kaikorai played precision rugby to score three tries at Bishopscourt and led 22-0 at the break.
The inside pairing of Josh Renton and Ben Miller gave the Kaikorai backs space and the forwards played with aggression. Miller kicked four goals to take his season's points to 113.
Miller demonstrated tactical kicking skills with an accurate kick into the corner and wing Matt Jones grabbed the ball for the try.
A rearranged backline gave Harbour spark in the second spell. Tala Fagasoaia was moved to halfback and Sio Tomkinson to first five-eighth.
The backline had more fluency and the forwards more aggression as Harbour scored three tries to reduce the gap to five points after 25 minutes.
Sio Tomkinson added sparkle and scored the best second-half try when he ran out of his own 22m, kicked ahead and won the race to the ball.
No8 Ben Whale, the best Harbour forward, made six clean lineout takes and James Tomkinson tackled his heart out. Replacement loose forward Charles Elton added stability in the second spell.
Openside flanker Slade McDowall's work at the breakdown made him the best Kaikorai forward. He was backed by prop Jonah Aoina who scored his ninth try of the season and lock Pita Sinamoni.
