Although Rooney scored from the spot in United's 3-1 win at Braga in midweek, he missed in last weekend's 2-1 win over Arsenal.
And Ferguson has told the United star that he cannot afford any more slip-ups.
"Wayne has to accept he has to have a better strike rate with penalties,' said the United boss. 'He has to produce better, but he's capable. His penalty the other night, even though he slipped, hit the target and that's important," the Daily Mail quoted Ferguson, as saying.
"You need to make sure the keeper has to make a great save. If he does, full marks to him. The one thing about Rooney is that it wouldn't matter if it was a World Cup final or a League Cup first round game against an amateur team, he would still want to score," he added.
Rooney has missed four penalties from nine in 2012 but the United boss said there was no question of him relinquishing his spot-kick duties.
"No chance. But he will not want to miss another one," he said. (ANI )