Ranked No. 536 and a regular on the second-tier Challenge Tour, Moriarty birdied three of the final four holes to help set the pace in Killarney.
Defending champion Ross Fisher of England, Sweden’s Niklas Lemke, Australia’s Richard Green and former winner Soren Hansen of Denmark joined Moriarty atop the leaderboard, but McIlroy dropped down the field by double-bogeying the par-4 last hole to cap a disappointing back nine.
The US Open champion, who made four birdies in the first 10 holes but finished with a 70, pulled off a spectacular shot from the thick rough at No. 14.
Bending a wedge shot round a huge oak tree, the Northern Irish star managed to hook the ball 50 yards (meters) to land it within 12 feet of the pin. Two putts salvaged a par.
“All I was trying to do was get it in the front bunker,” said McIlroy, who was playing his first event since a disappointing British Open, where he finished tied for 25th at Royal St. George’s.
McDowell, the 2010 US Open champion, shot 72 and was five shots off the pace.
British Open champion Darren Clarke of Northern Ireland and Ireland’s three-time major winner Padraig Harrington were among the afternoon starters.
The 32-year-old Moriarty, who received an invitation to play in the tournament, had six birdies.
“I played lovely all day. It’s the tournament you want to do well,” said Moriarty, who is playing his seventh event on the European Tour this season. “This is where you want to be playing week in, week out.”
A winner by two shots last year, Fisher had a bogey-free round featuring two birdies.
“I have fond memories of what I did last year and my game is in pretty good shape,” said Fisher, a member of the 2010 Europe Ryder Cup team.
Hansen, who won the tournament in 2002, bounced back from a bogey at the first hole with an otherwise error-free round, while Lemke would have held the outright early lead if he hadn’t bogeyed the last after hitting into the water off the tee.
McIlroy found the same stretch of water from a fairway bunker.
“I didn’t drive it great all day and I played some scrappy golf coming in,” the 22-year-old said.
In Carnoustie, Scotland, Brittany Lincicome shot a 5-under 67 to take the early clubhouse lead in the first round of the Women’s British Open on Thursday.
Five birdies and an eagle propelled the American to the top of the early leaderboard, despite picking up a couple of bogeys along the way.
“I didn’t take advantage of some chances on the front nine, but then really got going from the 12th,” she said. “This is a great golf course and it seems top suit my game really well so I’m looking forward to the next three days.”
Lincicome birdied the 2nd when she hit a gap-wedge to 15 feet and holed it. She dropped a shot at the long 6th when her drive was just an inch in bounds and she had to take a drop, before hitting her third into a greenside bunker and failing to get up and down.
She birdied the short 8th by holing from 40 feet just off the green, but then bogeyed the 10th.
The fireworks started with consecutive birdies at 12 and 13 before Lincicome hit a long drive on 14 and followed up with a 6-iron to 10 feet and holed that for an eagle before birdying the long 17th.
Fellow American Kristy McPherson got off to a flying start when she moved to 5-under within the first six holes.
McPherson birdied the 2nd, 4th and 5th holes before adding an eagle at the par-5 6th, and then parred the last three to be out in 31.
Compatriot Angela Stanford leapfrogged three players on 69 to take over the early lead with a 68. She picked up four birdies in the first seven holes, dropped a shot at the 9th, and then had three more birdies and two bogeys on the way home.
Sweden’s Caroline Hedwall hit the first tee shot of the day and then proceeded to card a 69, matched within the hour by Japan’s Momoko Ueda, then later by South Korea’s Na Yeon Choi.
The 22-year-old Hedwall, twice a winner on the European Tour this season and lying third in the tour rankings, dropped shots at 3 and 8 on the way out but picked up three birdies. She got to 2-under at the 10th, only to drop shots at 12 and 13 to go back to level. She finished with a flourish, however, with birdies at 14, 15 and 17.
Last year’s winner of the Evian Masters, Ai Miyazato, had a disastrous start by bogeying the first five holes on her way to a 76, while three-time former champion, American Sherri Steinhauer slumped to a 78.
