Ko shot a first-round 2-over-par 74 to languish in a tie for 79th, six shots behind the leader, American Ally Ewing, who carded a 68 to finish at 4-under for a one-shot lead.
Ewing was part of a six-way tie atop the leaderboard heading into the final three holes but eagled the 16th to move clear of Lee Jeong-eun, Emily Pedersen, Perrine Delacour, Jaravee Boonchant and Amy Yang.
World No 5 Ko’s round included four birdies, four bogeys and a double bogey, continuing her poor form this year. It also all-but scuppers her chances of breaking her seven-year major drought