The loss of key players and changes in personnel have left both sides a shadow of those that reached the play-offs last season, when Reading were beaten finalists at Wembley.
Creating clear-cut chances was a struggle. Forest had a goal chalked off and Reading fortuitously hit the bar in the early stages.
It looked destined for a goalless draw until Tudgay's control and shot on the turn settled the game in the 67th minute.
Substitute Noel Hunt would have snatched a point for Reading but for a superb injury-time save from Forest goalkeeper Lee Camp.
Guy Moussi returned to the Forest starting XI after suspension in one of two changes made by Steve Cotterill following his first defeat as Reds boss to Hull on Saturday the French midfielder replacing Jonathan Greening.
A hernia complaint that requires surgery kept Ishmael Miller, fined by the Football Association today for comments made on social networking site Twitter, out of the squad so Robbie Findley was recalled in attack.
Mathieu Manset came in for Simon Church in the only change made by Reading.
Forest had the ball in the net after 11 minutes when Radoslaw Majewski's cross ricocheted into the path of Tudgay.
The former Derby and Sheffield Wednesday striker finished superbly into the roof of the net from eight yards out but the referee's assistant had his flag raised for offside.
Reading's nearest effort came four minutes later when Jobi McAnuff's cross from the left curled over Camp and struck the bar.
The visitors threatened again in the 20th minute when Mikele Leigertwood's header back across goal found Adam Le Fondre at the back post, but the summer signing from Rotherham blazed over from a very acute angle.
Forest almost caught Reading out with a well-worked corner on the half-hour. Lewis McGugan drilled in a low ball around the penalty spot where Majewski had found space, but the Pole sent his shot wide.
McGugan created another opportunity five minutes before the break when his driven, low free-kick saw Tudgay benefit from another ricochet, but this time the 28-year-old's effort went over.
Another McGugan free-kick at the start of the second half caused Reading problems.
Goalkeeper Adam Federici, presumably distracted by players running across the flight of the ball, fumbled the inswinging cross before smothering the danger at the second attempt.
McGugan and Tudgay managed to get shots away from the edge of the area but Federici barely had to move to save either effort.
The breakthrough arrived just before the midway point of the second half. Reds captain Luke Chambers crossed from the right-hand side and, after killing the ball with his right foot 10 yards out at the near post, Tudgay turned and sent a shot with his left in off the far upright.
McGugan and substitute Andy Reid worked Federici from outside the area late on, before Tudgay did likewise in injury time.
Hunt came close to rescuing a draw for Reading but his header from eight yards produced a brilliant one-handed save from Camp.