The Cubs have lost five in a row to fall below .500 for the first time since May 28.
Davies (4-2) pitched four-hit ball into the seventh inning, helping Atlanta pull within 4½ games of first-place Washington in the NL East. He walked four but held an opponent scoreless for the fourth time in nine major-league starts.
The rookie has provided a big boost to a Braves rotation that has three starters on the disabled list, but manager Bobby Cox said, "LaRoche has got to get the star of the game tonight."
LaRoche hit .302 with 10 homers after the All-Star break last season to finish with a .278 mark, 13 homers and 45 RBI.
Still sharing time with Julio Franco at first base, LaRoche already has 11 homers and 50 RBI this season. He has three home runs in the first four days of July after hitting two in June.
"I've been feeling good the last couple weeks," LaRoche said. "It's been nice to come out of the funk I've been in."
All-Star outfielder Andruw Jones is the only Braves player with more homers or RBI than LaRoche.
A Turner Field regular-season record crowd of 52,274 saw the Braves win for the 14th time in 20 games.
LaRoche's two-run shot off Wood (1-2) highlighted Atlanta's three-run first inning. He added his 11th homer in the eighth inning for his second career two-homer game.
With one out in the sixth, Davies walked Jeromy Burnitz and gave up a sharp single to Aramis Ramirez. He pitched out of the jam by retiring Todd Hollandsworth and Neifi Perez, but was lifted after issuing a walk with two outs in the seventh.
Davies said he received a tip from John Smoltz between starts.
"He said my front leg was a little weak," Davies said, adding that he tried to finish his follow-through stronger on his landing leg this time.
"That's why my balls have been up," Davies said.
Making his second start since coming off the disabled list, Wood gave up six hits and three runs in five innings. He walked three and struck out six.
LaRoche followed with his two-run homer to center for a 3-0 lead.
"I made a few mistakes, and they hurt me," Wood said. "The hit by Jones was up the middle and then the home run. After that, I made better pitches. ... I felt strong. I thought I threw the ball pretty well after the first inning."
Cubs manager Dusty Baker said Wood "found the heart of the plate" on LaRoche's homer.
The Cubs wasted a scoring opportunity in the eighth. Burnitz walked with one out but was thrown out by Jones in center after taking a big turn at second and then trying to return to the bag on Hollandsworth's single.
LaRoche led off the eighth with his second homer, another shot to center, off Will Ohman.
Told that he was Cox's star of the game, LaRoche passed the honor on to Davies.
"That was very nice of him, but I'm going to give it to Kyle," LaRoche said. "For him to do what he did against that lineup, with as little experience as he's had, I can't say enough about him."
Baker said Davies "was pretty good."
"He kept the ball away, like Braves pitchers always do," Baker said.
- Cubs reliever Mike Remlinger plunked Johnny Estrada with a pitch in the sixth inning. The pitch hit Estrada's shoulder and then his helmet. Estrada, who suffered a concussion in a home-plate collision on June 6, stayed in the game.
- LaRoche's other two-homer game was Aug. 11, 2004, against Milwaukee.
- Davies began his major-league career by winning his first two starts, pitching a combined 10 1/3 innings in wins over Boston and the New York Mets.