Tullo's birdie on the par-3 helped him finish at 4-under 68 for the day, one shot ahead of Peter Uihlein (69) and Craig Lee (70).
The trio had been playing neck-and-neck until 17 when Tullo sank a clutch 10-foot putt to take the lead for good. Lee parred his last seven holes and Uihlen parred the final five holes after a bogey and three birdies to start the back nine.
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