"I'm one-for-one defending titles, so that's a pretty good stat", said Berger, who claimed his first and previously only PGA tour victory at last year's St Jude Classic.
South African Charl Schwartzel shot a 66 and South Korean Whee Kim shot a 67 to finish in second, one shot back.
"It was nearly like I was a rookie today because I saw".
Schwartzel shot a woeful 4-over 74 Saturday, but bounced back with a 4-under 66 in Round 4.
"There's no way that I can change my mindset and go out there and try and make pars - I won't win the golf tournament if I do that", Reavie said.
He started on the back nine and birdied four of his first eight holes, going back-to-back on Nos. After one round in Iowa, he's tied with two golfers who've never won on the senior circuit.
A headache that came on at the 11th hole before her run of birdies had gone away by the time Sharp signed her scorecard.
"The good news is that my physical game is there and I should be able to find the mental toughness here soon", Mickelson said.
Phil Mickelson made a dramatic charge and grabbed a share of the lead following his fifth birdie of the day at No. 10, but he doused his momentum and his chances with a triple bogey at the par-4 12th.
"I identified the problem and switched putters, thought about all the things I did as a junior".
Scott, meanwhile, was closer to the cut line than the lead for much of the day, but he stormed home with an eagle and two birdies in the final five holes to jump to equal 11th. Following a win at the St. Jude Classic yet again, the Plantation, Fla., native is planning to use this victory as more of a relaxer than anything.
Money leader Bernhard Langer finished at 12 under, while Scott Verplank, Tom Lehman and Steve Flesch were another shot back.
Jodi Ewart Shadoff of England (69) was one shot back in fourth place.
Schwartzel, the 2011 Masters champion, surged into contention with birdies on his first three holes. South Korea's Mi Hyang Lee (68) and Laura Gonzalez Escallon of Belgium (67) were at 14 under.