Rory McIlroy and Tiger Woods are six shots off the pace at the halfway stage of the Farmers Insurnce Open at Torey Pines.

McIlroy shot two birdies and three bogeys on Friday for a one-over round of 73, putting him on four-under-par alongside Woods, who posted an up-and-down 71 in his second round.

Ryan Palmer fired a sensational 10-under-par 62 to seize the lead.

The American had been worried about missing the cut at the PGA tournament after slipping to three-over through his first eight holes of Thursday. He recovered to make an even-par 72 but was still six shots off the first-round lead.

Ryan Palmer has taken a two-shot lead

On Friday, however, he set the course alight with a superb display, which would have been even better but for a bogey on the final hole.

"I knew today when I got out here, the low rounds were out here," said Palmer. "A good five- or six-under-par round was to be had. I just took what I had and it turned into a 62."

Palmer earned a two-shot lead over compatriot Brandt Snedeker, who fired a 67 on Friday.

American JB Holmes sat third, a further shot away following opening rounds of 68 and 69.