On a 0-1 pitch, Ludwick hit his first homer of spring, a liner that landed on the grassy berm in left field.
The Padres' Opening Day starter, Edinson Volquez allowed just one run and two hits in his five-plus-inning start. But in typical Volquez fashion, he labored with a lot of pitches throughout his final spring outing and walked six while striking out one.
"He had a no-hitter into the fifth," Padres manager Bud Black said. "His stuff was good, but his command got away from him a little. But he came back to get the out when he needed to. I think he's ready for Monday."
Mike Leake, the Reds' No. 5 starter, completed six innings and allowed one run and five hits with no walks and four strikeouts.
With two outs in the top of the second against Leake, Cameron Maybin hit a single to center field and scored on Kyle Blanks' RBI double off of the wall in right-center field for a 1-0 lead.
Facing Volquez in the fifth with one out, Choo became the first Reds batter to notch a hit with his second homer of the spring, a solo shot the opposite way to left field.
The Reds added three runs in the eighth with a run-scoring single from Brandon Phillips and a two-run homer by Votto.
Padres Up Next: The Padres play their final Cactus League game at 12:05 p.m. PT on Thursday against the Indians at the Peoria Sports Complex, available on Gameday Audio. Clayton Richard, the No. 2 starter in the rotation, makes his final exhibition appearance. He will most likely work in upward of seven innings. The next time Richard pitches in a game will be April 3 against the Mets at Citi Field in the second game of the regular season. So far this spring, Richard has a 6.59 ERA in 13 2/3 innings.
Mark Sheldon is a reporter for MLB.com. Read his blog, Mark My Word, and follow him on Twitter @m_sheldon. This story was not subject to the approval of Major League Baseball or its clubs.