Rory McIlroy has made a disappointing start to his challenge at the Honda Classic

The world number one carded a double-bogey for his first hole in Florida and has now slumped to 3-over par after eight holes.

Earlier, Graeme McDowell laboured his way to a 4-over par 74 at Palm Beach.

In contrast, Padraig Harrington is tied for fourth place and just 2 shots off the lead on 3-under par after shooting a 67 for his opening round.

Jim Herman leads on 5-under after completing his round.

On the European Tour, Peter Lawrie is three shots off the lead on 5-under after a 66 on day one of the Joburg Open in South Africa.

Kevin Phelan is 4-under and Gareth Maybin is another shot back.