Ryan Dempster’s new, authoritative approach has paid off.He struck out a season-high 11 and snapped a six-game Wrigley Field losing streak to help the Cubs beat the San Francisco Giants 11-4 Friday.Dempster (2-4) allowed two runs and six hits in six innings and the Cubs ended San Francisco’s six-game winning streak. Reed Johnson went 3 for 5 and drove in four runs, three on a bases-loaded triple in the seventh. Darwin Barney was 3 for 5 with 3 RBI and Starlin Castro also had three hits, and drove in two runs.Giants left-hander Madison Bumgarner (0-6) gave up two earned runs on five hits through six innings, struck out six and walked two. He hasn’t won since Sept. 30, 2010.Cody Ross hit a two-run homer in the eighth that cut the margin to 8-4. But in the bottom half, the Cubs added three more runs on Castro’s double, Barney’s single and Johnson’s two-out blooper to left field.Dempster struck out Ross his first two times up.Barney’s RBI double off Jeremy Affeldt in the seventh kicked off a five-run outburst. Affeldt then hit Marlon Byrd with a pitch to load the bases before departing. Jeff Baker singled off Guillermo Mota and Johnson followed with a two-out triple.Aubrey Huff drove in the Giants’ first two runs, on a single in the first inning and a double in the fifth. In between the Cubs scored three runs in the bottom of the second. Koyie Hill had a sacrifice bunt, and then came home on Castro’s single with two outs. Barney added a single.

NOTES—A first-inning infield single extended Cubs Byrd’s hitting streak to 14 games….Until Friday, each of the Giants’ previous 19 games had been decided by three or fewer runs, and they led the league in one-run games with 15…..Saturday’s night game against the Giants will be the first Saturday night game at Wrigley Field in nine years…..Cubs right-hander Randy Wells, on the disabled list with a forearm strain, is scheduled to make a rehab start against Quad Cities next Tuesday at Class A Peoria…..Giants right-hander Ryan Vogelsong (2-0) will make his fourth start of the season on Saturday night against Cubs left-hander Doug Davis, who is making his first career start after being promoted from Triple-A Iowa.