SAN FRANCISCO -- Travis Wood held the San Francisco Giants to four hits in seven innings and helped his own cause with a home run, and batterymate Welington Castillo broke a seventh-inning tie with a solo shot as the Chicago Cubs completed a three-game sweep of the defending champions with a 2-1 victory Sunday.
The Cubs finished a 6-4 Western trip by wrapping up their first series sweep in San Francisco since September 1993. Chicago began the trip by going 1-2 at Colorado and 2-2 at Arizona.
Meanwhile, the defeat saddled the Giants with a four-game losing streak as they prepared to fly cross-country for Monday's annual champions' visit to the White House. It will be the Giants' second up-close-and-personal with President Barack Obama in the past three years.
Wood, the Cubs' lone All-Star representative earlier this month, turned in his 18th quality start in 21 outings. He walked four and struck out seven. The only run he allowed was unearned.
Two of the four hits permitted by Wood (7-7) were by counterpart Tim Lincecum (5-11), who entered the game with an .056 batting average.
After the teams traded fifth-inning runs, Castillo provided the difference-maker with two outs in the seventh. The blast into the left field bleachers came on a 3-1 pitch as Lincecum chose to challenge the No. 8 hitter rather than walk him and deal with Wood, who already had two hits, including his third homer of the season.
The home run also was Castillo's third of the year.
Pedro Strop pitched a scoreless eighth inning before turning the ball over to closer Kevin Gregg, who recorded his third save in three nights and 22nd of the season. The Cubs (48-55) improved to 33-27 outside the National League Central.
Lincecum, two starts removed from a no-hitter in San Diego on July 13, allowed only four hits in seven innings. However, he fell victim to the two home runs, the 14th and 15th he's allowed this season, including five in his past two games.
The former two-time Cy Young Award winner walked two and struck out 10, his third double-digit strikeout effort of the season and the 36th of his career.
Wood's home run came with two outs and two strikes in a scoreless game in the top of the fifth. He leads all major league pitchers with three home runs, and the RBI was his eighth, tied with former teammate Scott Feldman for the major league high by a pitcher.
San Francisco got even in the bottom of the inning. Lincecum singled off Wood, and he eventually was tagged out at the plate on a double-play grounder by Buster Posey, but Pablo Sandoval followed with an RBI double to left field to score Marco Scutaro.
The Giants, who began the day having recorded two or fewer hits with runners in scoring position in 26 of their previous 32 contests, went 2-for-8 under those circumstances, with Hunter Pence three times ending innings with two teammates on base.
Fittingly, the game ended when pinch hitter Gregor Blanco popped out to shortstop one pitch after Kensuke Tanaka stole second base and took third on a throwing error by Castillo.
Cubs rookie sensation Junior Lake went 0-for-4 to complete an 0-for-12 series. He began his major league career with a seven-game hitting streak earlier in the trip at Colorado and Arizona, recording 15 hits in those games.
NOTES: Only one other pitcher -- Milwaukee's RHP Yovani Gallardo -- has hit more than one home run this season. Gallardo has two. ... The last-place Giants (46-58) fell to a season-worst 12 games under .500. ... Giants 1B Brandon Belt, whose two-out, ninth-inning error allowed the tying and winning runs to score for the Cubs in Chicago's 3-2 win Friday, went 0-for-4 with four strikeouts Sunday. ... While the Giants are visiting the White House, the Cubs will be opening a seven-day, eight-game homestand Monday. Lake is expected to make his Wrigley Field debut Monday in the opener of a four-game series against Milwaukee. ... Neither team took batting practice before the game, but that didn't stop the Cubs from cheering a morning home run. Many Chicago players were watching on television in the clubhouse when former teammate Alfonso Soriano belted his first homer for the New York Yankees.