The 27-year-old, who has missed nine of his 26 spot kicks in all competitions for United, failed to convert his penalty against Arsenal last weekend and almost missed from 12 yards against Sporting Braga in midweek.
"I think that Wayne has to accept it," said Ferguson. "He has to have a better strike rate with penalties.
"The penalty he took the other night, even though he slipped, it's still well hit and it's hit the target. You know, I think that's important to hit the target.
"I think he has to accept that he has to produce better. I mean he is capable of hitting them."
However, Ferguson insists that Rooney is mentally strong enough to take penalties under pressure.
"The one thing about Rooney is it wouldn't matter if it was the World Cup final or a first-round game against an amateur team, he would want to score, there's no doubt," said the 70-year-old.
"And his temperament is that, if he misses, it won't affect him. But that's important for a penalty-kick taker, that it doesn't affect them if he were to miss and that's an issue with a lot of people taking penalty kicks is if they miss it, how they handle it.
"Because of Wayne's temperament, it's good that way."
Rooney has scored three goals in 11 competitive matches so far this season.