This was followed by a disappointing 3-2 loss to North Harbour on Day 2 as temperatures hit 30 degrees.
North Habour's leading player Jason Gulasekharam defeated Munn on the final hole in their game.
"He gave me a hiding last year. Josh went scuba diving he was shooting so low, but I was always looking forward to this match and hoping to get one back at him," said Gulasekharam.
After spraying his drive on the 18th hole, Gulasekharam produced a spectacular up-and-down from 71m and stuck it to four feet and halved the hole.
"I have never been so nervous over a four foot putt in my life," said Gulasekharam.
Manawatu-Wanganui rebounded to beat Poverty Bay-East Coast 4-1 on Wednesday afternoon, with only Ring not getting on the winners sheet against Peter Kerekere, while McDonald defeated William Brown 5/4.
But yesterday the team was defeated 3-2 by Bay of Plenty and were looking at a hard road to hoe for the remainder of the tournament after McDonald was beaten by Landyn Edwards 3/1 and Ring lost to Sam Davis 8/7.
Manawatu-Wanganui will now play Canterbury this morning and then title contenders Waikato this afternoon to see if they can scrape through to the final four.
-Results
Round 2 - Manawatu-Wanganui bt Aorangi 3.5-1.5: Lachie McDonald square with Jordan Green; Hayden Ring square with Garth Simpson; Regan Cording bt Daniel Perham 1up; Josh Sedgwick square with Jeff Hewitt; Junior Tatana bt Jeremy Goodman 2/1.
Round 3 - Manawatu-Wanganui lost to North Harbour 3-2: Josh Munn lost to Jason Gulasekharam 1up; Lachie McDonald bt Mark Hutson 5/4; Hayden Ring lost to Chang-gi Lee 2/1; Regan Cording bt Jake Meenhorst 1up; Josh Sedgwick lost to Cameron Jones 2up.
Round 4 - Manawatu-Wanganui bt Poverty Bay-East Coast 4-1: Josh Munn bt Nathaniel Cassidy 3/1; Lachie McDonald bt William Brown 4/3; Hayden Ring lost to Peter Kerekere 5/4; Regan Cording bt Tony Akroyd 1up; Josh Sedgwick bt Andrew Higham 5/3.
Round 5 - Manawatu-Wanganui lost to Bay of Plenty 3-2: Josh Munn bt William Howard 1up; Lachie McDonald lost to Landyn Edwards 3/1; Hayden Ring lost to Sam Davis 8/7; Regan Cording lost to Jordan Golding 5/4; Josh Sedgwick def Henry Spring 2up.