The 39-year-old was charged in relation to a breach of FA Rule E3 concerning media comments, which implied that the match referee and/or match officials in general are motivated by bias and/or brought the game into disrepute.
Martinez, who had requested a personal hearing, was also warned as to his future media conduct.
| WIGAN LATEST
|10/1||Wigan are 10/1 to beat Everton 1-0 with William Hill|
Martinez felt the England forward went down too easily under a challenge from Ali Al-Habsi to win a penalty for the home side (although the goalkeeper saved the resulting spot-kick), and thought the 21-year-old could have been sent off for a late challenge on Franco Di Santo.
"I have come to United three times before today and for whatever reason we don't seem to be measured in the same manner as the team at home," he told reporters.
"Today the penalty is as bad a decision as you are going to see in the Premier League. In many ways, you feel as though you are fighting against a mountain.
"There were tackles flying around that if they had been the other way round there would have been a couple of red cards."