Angel Pagan hit a three-run home run in San Francisco's five-run eighth inning and the Giants beat Arizona 8-5 on Thursday in a game that was halted briefly in the top of the first due to a swarm of bees in the outfield.
Paul Goldschmidt and Mark Trumbo each hit two-run homers and Arizona led 5-3 after seven, but the Giants teed off on reliever Will Harris (0-1) in the eighth to take three of four games from the Diamondbacks.
"We're just trying to be patient, not panicking when we're trailing on the scoreboard," Pagan said. "And it's been working. Everybody's putting the best at-bat possible for the next guy to get the job done. It happened to me in that at-bat."
Belt, who had no home runs and only two RBI in the spring, joined Barry Bonds, Willie Mays and Kevin Mitchell as the only Giants with three home runs in the first four games of a season.
"I said before the season I would hit 74 home runs," he quipped. "So we'll see what happens."
Goldschmidt homered in the first inning off Tim Lincecum, his sixth home run in 21 career at-bats against the Giants right-hander.
"I'm going to start throwing underhand to him," Lincecum said. "I don't know, I've just got to figure out something."
Jean Machi (2-0) got one out for the victory.
Machi also got the victory in the season opener.
Goldschmidt extended his hitting streak to 25 games, second-longest in franchise history. He also doubled to improve to 12 of 23 against Lincecum with 13 RBI.
With a pair of season-opening losses to the Los Angeles Dodgers in Australia, Arizona has started the season 1-5.
Bronson Arroyo, sidelined most of the spring with a sore back, was lifted after 4 1/3 innings in his Diamondbacks' debut.
Pagan, who had three hits, homered on the first pitch after the Giants tied it at 5.
"It was down and over the plate," Arizona manager Kirk Gibson said. "He is very aggressive and he smoked it."
With the Diamondbacks leading 5-3, Hunter Pence drew a one-out walk in the eighth and scored on Hector Sanchez's double. Pinch-hitter Buster Posey was walked intentionally and Michael Morse's pinch-hit single up the middle tied it. That brought up Pagan, who hit the first pitch into the swimming pool area in right field to put San Francisco on top.
Arizona's Aaron Hill had three hits, including an RBI double, and scored twice.
Belt's two-out homer off Arroyo in the first inning, his third in his first 14 at-bats this season, put the Giants up 1-0.
Hill singled with one out in the Arizona first to bring up Golsdschmidt, who hit the first pitch he saw into the pool area.
San Francisco tied it at 2 in the fourth. Pablo Sandoval led off with a double down the left field line, advanced to third on Pence's single and scored on Sanchez's sacrifice fly to center.
Arroyo gave up a leadoff double to Pagan to start the fifth. Pagan took third on Gregor Blanco's sacrifice bunt and Arroyo's day was over. Left-hander Oliver Perez got Belt and Sandoval to pop out to end the threat.
Hicks' shot to left off Josh Collmenter with one out in the seventh cut the lead to 4-3. It was his fourth career home run, first as a pinch hitter.
Arizona added a run with two outs in the seventh, Hill doubling to the wall in left off Machi to score Gerardo Parra from first.
The Diamondbacks' franchise-record hitting streak is 30 games by Luis Gonzalez from April 11-May 18, 1999. ... The Giants will play a weekend series with the Dodgers in Los Angeles, sending RHP Ryan Voglesong to the mound Friday night. LHP Hyun-Jin Ryu goes for the Dodgers. Arizona opens a three-game series in Colorado Friday, going with RH Randall Delgado against Rockies RH Juan Nicasio.