CHICAGO -- Jake Arrieta overcame one bad inning to help the Chicago Cubs continue their dominance over the Pittsburgh Pirates.

Arrieta struck out a season-high 11 and allowed two runs and three hits in eight innings as the Cubs beat the Pirates 8-2 on Saturday afternoon.

The Cubs have outscored the Pirates 37-11 in winning all five games against their National League Central rival this season. Chicago owns baseball's largest run differential over opponents at 213-103.

Addison Russell and Anthony Rizzo homered for the Cubs, who also have the majors' best record at 27-8.

Arrieta (7-0) earned his 18th straight winning decision, and the Cubs have won his last 21 starts. The reigning NL Cy Young winner last lost on July 25, when the Philadelphia Phillies' Cole Hamels threw a no-hitter against the Cubs.

Arrieta most recently struck out 11 on Sept. 22, 2015, against Milwaukee.

Russell homered for the second straight day, hitting a two-run shot, and Dexter Fowler followed with an RBI single in the sixth for a 6-2 Cubs lead. Russell has four home runs this season.

Rizzo hit his 11th home run, a three-run shot, to put the Cubs ahead 3-2 in the fourth.

Francisco Cervelli's two-run single gave the Pirates a 2-0 lead in the top of the fourth. Arrieta allowed three hits and hit Jung Ho Kang with a pitch on the back before a double play got him out of the inning.

Kris Bryant and Rizzo added RBI singles off reliever A.J. Schugel in the eighth. Rizzo finished with four RBIs. Jason Heyward had three hits. Pirates starter Jeff Locke (1-3) allowed six runs and six hits and struck out three in 5 1/3 innings.

The Pirates finished with three hits and fell to 3-4 on their current road trip.

NOTES: The Cubs activated C Miguel Montero (lower back tightness) from the 15-day disabled list and designated OF Ryan Kalish for assignment before Saturday's game against the Pirates. Montero went on the DL on April 25. He was hitting .208. ... The Cubs now have three catchers with David Ross and Tim Federowicz, giving the team some flexibility for moves later in games, manager Joe Maddon said. Federowicz has been playing well, forcing the Cubs to keep him, Maddon added. ... Cubs OF Matt Szczur (mild right hamstring strain) is eligible to come off the 15-day DL on May 18. Maddon said Szczur is moving well. ... The temperature at first pitch was 44 degrees, with a wind-chill of 39 degrees. ... Pirates pitching coach Ray Searage was ejected during a mound visit in the fourth inning after Locke issued two walks.