Giants 5, Astros 1: Buster Posey homered and Madison Bumgarner tossed seven solid innings as host San Francisco opened the second half with a win over Houston.

Bumgarner (11-5) rebounded from his worst outing of the season by giving up one run on two hits. Santiago Casilla struck out the only two batters he faced with two runners on in the ninth for his 22nd save.

Posey gave the Giants an early lead in the first with a two-run blast measured at 448 feet off Wandy Rodriguez (7-7), who allowed four runs over six innings.

San Francisco opened the second inning with back-to-back singles before Joaquin Arias drove in Angel Pagan. The Giants added another run when Brandon Belt scored on Justin Christian’s grounder.

Chris Snyder ruined the Giants’ shutout in the seventh with a two-out solo blast off Bumgarner, who gave up a season-high seven runs in five innings against Washington last Wednesday.

Pablo Sandoval, who tripled in Tuesday’s All-Star game, hit a triple to deep right field in the eighth inning and scored on Pagan’s sacrifice fly when he barreled into Snyder and knocked the ball loose.

San Francisco won for the third time in its last 10 games, while Houston has one victory in its last 12 games and owns the majors’ worst record.

GAME NOTEBOOK: Astros CF Justin Maxwell (ankle) was activated from the 15-day disabled list prior to the game and went 0-for-3. … Bumgarner has given up one run on three hits with 13 strikeouts in his last two home starts covering 16 innings. …Rodriguez has gone five or more innings in his last 48 starts, which is the longest active streak in the National League. …The Giants improved to 27-16 at AT&T Park.