Dumatrait surrendered one run on four hits and a walk while striking out four in seven innings. The 26-year-old left-hander is 2-0 with a 1.89 ERA in his last three starts.
Bill Bray (1-1) allowed one hit and fanned one in the eighth for the win and Gary Majewski tossed a perfect ninth for his third save.
Mark Bellhorn ripped a solo homer, his 11th, in the eighth and Ryan Hanigan and Joey Votto hit RBI singles for the Bats (49-45).
Scranton/Wilkes-Barre starter Matt DeSalvo (6-2) allowed two runs on three hits and two walks while striking out six in 7 1/3 frames.
Andy Cannizaro singled in the third to extend his hitting streak to 10 games and scored the lone run for the Yankees (50-42) on an error.