The Posh goal scorer was Jonson Clarke-Harris, who put away a Siriki Dembele pass four minutes before half time. An ankle injury brought a premature end to Clarke-Harris's game, but one goal proved to be enough to see off a Plymouth side that is still searching for away success this season.
After the match, Ferguson said: "Football is so fickle. We've had two defeats and justifiably taken criticism for how we played in those games.
"It was important not to let that run get to three and our performance was very good as we played our system as well as we have ever done.
"We produced our best first half of the season and just needed the second goal to relax us a bit and kill it off. We had so many opportunities to get it and on another night we could have scored four or five quite comfortably, but it didn't happen.
"That gave Plymouth hope when the game should have been over but the clean sheet was very important and overall I'm delighted.
"We're picking up two points per game, which is always our target, and we’re ticking over nicely. Nine wins out of 14 games is a very good start."
Posh remain in second place in the Sky Bet League One table after Hull City won their match at Ipswich.