Canadian Rick Gibson maintained his good form from yesterday by shooting a two-under-par 68 with nine holes to play and a share of the lead with Erlandsson.
Paul Casey's woes continued on the front nine of his second round, dropping two shots and slipping to six over.
Birdies at the fourth and eighth left Thomas Bjorn, of Denmark, at two under as he moved to within five shots of the lead.
Gibson took the outright lead with birdies at the second and fifth in a round that, with four holes to play, had not witnessed a dropped shot.
A birdie at the 10th lifted Casey to five under par, while Bjorn picked up a shot at the same hole to move to three under.
Damien McGrane leads the Irish challenge, trailing Gibson by eight shots at one-under-par.
