Rooney score twice in England's World Cup qualifier win in Belarus on Wednesday and says he is in the best form of his international career.
Ferguson said: "What we have noticed is when he goes on one of his bursts, his performances improve with it."
"That is how it has been since he has been with us. We know he can score. It is a matter of getting consistency."
Both Ferguson and England coach Fabio Capello have tried to tinker with Rooney's game this season in a bid to get him to adopt a more selfish approach.
He has now hit a hot scoring streak, but Sir Alex Ferguson admits Rooney will never be a goal-poacher in the Gary Lineker mould.
"Some goalscorers I have seen, like Lineker, never kicked a ball in the game but score two goals," he said.
"Other players do not accept that. They feel they have to play well. Wayne Rooney is one of them. But he will get to a period when he scores goals even though he is not particulary playing well."
Source: BBC Sports.
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