Bubba Watson shot a second successive 64 to win the Northern Trust Open in California, his first title since lifting the 2012 Masters.

The American carded seven birdies - five of which came in the opening eight holes - during a blemish-free final round to finish the tournament on 15 under par and win by two shots from compatriot Dustin Johnson.

Johnson finished with a 66, while Jason Allred and Brian Harman were tied for third place on 12 under after both recorded final-round 68s.

South Africa's former Masters champion Charl Schwartzel, the only non-American in the top 10, was fifth on 11 under after he signed for a third consecutive 68.

Watson, whose win was his fifth on the PGA Tour, put his victory down to avoiding any dropped shots in his final two rounds after starting off with a 70 and 71 on the opening two days.

"I was bogey free on the weekend and that was the key," the 35-year-old said.

"I made the cut I think at one under and just went into the weekend trying to play solid golf and trying to build on it.

"I went out and went bogey free and made seven birdies so jumped up there and had a chance. (Today) I got hot early, holed a bunker shot on six to really get it going and went bogey free again. So it was a nice."

FULL RESULTS

Runner-up Johnson admitted it was difficult to compete when somebody produces scores like Watson managed.

"When you shoot 14 under on the weekend, it's tough to beat that," he said.

Overnight leader William McGirt, who started the final day with a two-shot lead over George McNeill and Charlie Beljan, was among a group of four players on 10 under after seeing his challenge ended by a disappointing two-over-par 73.

McGirt started well with a birdie on the first but then dropped shots at the second, ninth and 16th as he finished five shots adrift of Watson.

McNeil also ended on 10 under after closing with a level-par 71, while Beljan was two shots further back after a 73.

Of the European contingent, England's Lee Westwood was the best-placed finisher after a closing 71 left him on six under.

Padraig Harrington missed Friday's cut by two shots and Darren Clark did not appear on Friday because of a chest injury, after an opening 78.