In the final round at Huntingdale in Melbourne, which he began only three shots from the lead, Barnes slammed his club into the ground after his first wayward tee shot on his way to a 78.
He also five-putted the 15th hole from about four feet, carelessly knocking the ball around with his putter without lining it up. After hitting a wayward shot off the 17th tee, he again slammed his club into the ground.
Barnes was also shown on television hitting a tree with his club in Saturday's third round.
'From the word go, from the first shot he was blowing up,' said Barnes' Sunday playing partner Richard Green, who went on to win the tournament on the first extra hole of a playoff. 'It was a shame that that sort of behavior was going on.'
Green, an Australian, said the 23-year-old Barnes did not offer an apology for his behavior.
'I've seen him play before and I've seen what sort of antics he does get up to. I just put it aside and focused on what I needed to do,' Green told Sydney radio station 2KY on Monday.
Barnes later apologized to tournament director Andrew Langford-Jones after receiving a reprimand. Langford-Jones said he fined Barnes a 'substantial' amount but would not disclose how much.
'I informed him that I thought that his conduct was unprofessional, and he received a fine for it,' Langford-Jones said Monday.
He said there had been complaints from members of the public 'who thought it wasn't the image the game should be portraying.'
Langford-Jones said other players had also been fined for showing their temper on the course during the tournament, but he would not name them.
'It's a normal occurrence,' he said. 'We don't condone it. It might happen once a week where someone loses the plot a bit on a shot they've played, but all in all they're pretty well behaved.'
He said Barnes understood why he had been reprimanded but was disappointed to be fined.
'He felt the fact that's four or five-putted from four feet had already cost him a decent whack of money and he was a little bit disappointed that he got fined again.'
Barnes finished tied for 40th Sunday and won 5,250 Australian dollars ($3,950).
Asked if Barnes would be welcome back in Australia, Langford-Jones said: 'Certainly. He's been great for the game out here. He's an exciting young player and the crowds love him.'
Barnes plays frequently on the Australasian tour. It was his third tournament in as many weeks, having earlier played in the Australian Open in Sydney, where he missed the cut, and the Australian PGA at Coolum in Queensland state, where he finished tied for 20th.
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