The 23-year-old Delariarte, playing out of Southwoods, barely missed tying the course record when he bogeyed the 17th from the deep right bunker and his birdie try from 18 feet on the last hole lipping out of the cup.
Dizon made a grievous bogey on the par-5 fourth of the Wack Wack west course where he went for the green but landed on a tough lie in the bunker instead. He settled for an even-par round.
He was tied with ex-pro Dave Hernandez and Erwin Vinluan, who teamed up with Noli Kempis to win the National pro am at Riviera last year, as the top guns hardly created a stir on a hot, humid day.
Reigning Philippine amateur champ Angelo Que, feeling tired after playing six straight rounds last week, could only score a 73 like veteran Tommy Manotoc.
Jong Laput was alone at 74, a stroke ahead of Juvic Pagunsan, the Southeast Asian Games hero who was joined at 75 by national teammate Boyet Zaragosa, Antolin Victoria and Ronnie Torrecampo.
The tournament is sponsored by Northwest Airlines, Bridgestone/Tourstage, Cleveland, Hogan, Adams, Never Compromise, Ogio, Kasco, Greg Norman Apparel, Discovery Suites and Le Soleil in Boracay.
Jungolfer Judson Eustaquio also gave a good account of himself with a 76 that left him tied for 12th with three others.
The other notables who had struggling starts were Jingy Tuason (77), Cookie LaO (78) and Artemio Murakami (79).
"I felt very comfortable with my swing and my game as a whole. I made a big putt on the 11th and my round could have been better if not for that late bogey," said Delariarte, son of an Indonesia-based financial analyst.
Delariarte started his round with a birdie from 12 feet and had an easy birdie on the seventh for a 34 in the front nine. He two putted from 60 feet on the 10th for his third birdie, buried another from 30 feet on the next hole then sank a 12-footer on the 14th to go five under.