Landicho played the first 10 holes with a one-under card but collapsed with a maze of six bogeys on the last eight holes, finishing the round just two strokes clear of Taiwan bet Shih Huei Ju and two other local campaigners.
Also scoring 78s were 1988 winner Ruby Chico Walker and jungolfer Sarah Jane Esguerra.
Aileen Yao, who once reigned as a world age-group champion, and jungolfer Jayvee Agojo fell three strokes behind with their contrasting rounds of 79.
"Mahaba ang course, kailangan talaga malakas ang drive mo," said Landicho-Sales, who became a member of the national pool last year but still waiting for her first stint in an international competition.
Ex-titlists, Carmelette Villaroman-Calimag (1993) and Grace Ebalde (1980) both struggled under the tough conditions of the same course where the Philippine Open will be played. Ebalde carded a 90 while Carmelette slipped with an 83.
Landicho actually hit just two greens in regulation, the third and the 10th, but birdied both of them. Her brilliant putting touch saw Landicho salvage par nine times.
"I just got lucky on some putts, my putter saved me at least nine strokes today," said Landicho. "I wasn’t really feeling well when I teed off, may lagnat ako but I just tried to keep my focus."
Landicho added that her early tee-off also helped her a lot.
The event lost one of its top favorites when Lina de Guzman failed to show up due to an injured knee.