BOONE, N.C. — Jamal Jackson threw for three touchdowns and Appalachian State’s defense stood firm in the fourth quarter in a 24-17 victory over previously unbeaten Georgia Southern on Saturday.

Jackson found Brian Quick for a 15-yard touchdown pass with 9:24 remaining, their second scoring connection of the game. The Mountaineers (6-2, 4-1 Southern Conference) then stopped the Eagles (7-1, 5-1) three times in Appalachian State territory, including once after an interception gave Georgia Southern a first-and-goal at the 9.

Former Flowery Branch quarterback Jaybo Shaw struggled in the game, throwing two interceptions in the first half after not throwing one in his previous 63 passes over the first seven games of the season.

The Eagles, who came in ranked first in the Football Championship Subdivision coaches poll and had been averaging 369.7 rushing yards a game — best in the FCS — were held to 135 on the ground and 201 yards total offense by Appalachian State.

The Mountaineers, who have won or shared the last six conference titles, avenged last year’s 21-14 overtime loss to the Eagles, which ended their 26-game conference winning streak.

Georgia Southern, Appalachian State and Wofford all have one conference loss, with Appalachian State’s coming to Wofford. The Terriers, who host Georgia Southern on Nov. 12, have lost to Furman.

Two of Jackson’s touchdown passes came in the first half, including a 56-yarder to Quick with 17 seconds remaining, as the Mountaineers took a 17-3 halftime lead. Jackson, who took over as the starter three games ago, finished 13-of-26 for 222 yards, his third straight game of 200 or more yards passing.

Georgia Southern rallied to tie the game 17-17 in the second half. JJ Wilcox’s 3-yard touchdown run ended a 60-yard, 12-play drive in the third quarter and Darreion Robinson returned a punt 46 yards for a score on the third play of the fourth quarter.

Appalachian State responded with a 67-yard, nine-play drive that ended with Quick’s second scoring reception. Quick, the Mountaineers’ career leader in touchdown catches, finished with four receptions for 119 yards.

After Georgia Southern reached the Mountaineers 48 and punted to the 2, Laron Scott gave the Eagles a big opportunity by intercepting Jackson’s pass at the 35 and returning it to the 9. But a run by Jerick McKinnon was stopped for no gain, Shaw threw incomplete twice and McKinnon’s fourth-down pass was broken up by DeAndre Presley, now at cornerback after losing his quarterback job to Jackson.

Georgia Southern held Appalachian State on its ensuing possession and got the ball at its 45 after a punt, but was unable to pick up a first down.