Jeff Karstens pitched seven crisp innings, Pedro Alvarez homered and the surging Pittsburgh Pirates beat the Miami Marlins 3-0 on Sunday for their fifth consecutive win.

Pittsburgh completed its fourth sweep of the season -- all at home -- while matching its longest winning streak since Sept. 17-22, 2010. The Pirates (54-40) remained a half-game behind NL Central-leading Cincinnati.

Miami has lost five straight, scoring a total of seven runs during the slide.

Alvarez's fourth homer in his last six games and No. 21 for the season came after Casey McGehee led off the seventh with a double, making it 3-0.

Karstens (3-2) allowed five hits. Jared Hughes worked a perfect eighth and Joel Hanrahan retired the Marlins in order for his 28th save in 31 opportunities.