A game of few chances saw both sides struggle to carve out clear opportunities at goal before Wylde settled matters 11 minutes from time with a goal from outside the area worthy of winning any game.
The home side enjoyed a lot of early possession and forced a succession of early corners after Kenny McLean’s long-range effort was saved by Ross County goalkeeper Mark Brown.
Brown’s intervention was necessary again prior to the midway point in the half, saving efforts from McLean and Paul McGowan.
Chances were at a premium for the away side in the first 45 minutes with the best falling to Melvin De Leeuw who had his shot blocked.
Richard Brittain also went close for County before the break but his effort went wide of Christopher Dilo’s right-hand post.
St Mirren began the second half the way they had done the first with Steven Thompson and McGowan spurning early chances.
But County almost took a surprise lead when a right-footed free-kick from Brittain thundered off the crossbar.
The near-miss seemed to give the away side confidence and on three occasions Alex Cooper went close to putting them in front only to be denied by Dilo.
But Wylde made the all-important breakthrough for St Mirren after a stunning long-range strike which beat Brown to his top left corner in the 79th minute.
McLean had chances to extend St Mirren’s lead but was denied, once by a save from Brown, and once by the keeper’s right post.
Rocco Quinn almost got an unlikely equaliser for County in the 89th minute but saw his shot thunder off the crossbar as the game ended in defeat for Derek Adams’ side.