TORONTO (Bloomberg) — Canadian stocks tumbled the most in almost eight years, led by a record drop in raw-material shares, as tighter credit, rising unemployment and lower home prices threatened to tip the U.S. into a recession.

Potash Corp. of Saskatchewan Inc. fell the most since 1989 after rival Mosaic Co. posted profit that missed analysts' estimates and cut its sales forecast.

Barrick Gold Corp. plunged the most in two decades as bullion declined on speculation the US will approve a $700 billion plan to revive credit markets, reducing the metal's appeal.

Suncor Energy Inc. touched the lowest in 15 years, leading oil and gas producers lower as crude fell below $95 a barrel and Merrill Lynch & Co. said it may drop to $50. The Standard & Poor's/TSX Composite Index fell 7 percent to 10,900.54.

"Commodities are getting pummeled," said Martin Anstee, a fund manager at Stone Asset Management in Toronto, which oversees about $800 million.

"People are forecasting a wall of recession, which means lower commodity prices. We had a good run on higher commodities — now we're taking it in the neck."

Canada's main stock benchmark has slid 28 percent from its June 18 record to the lowest since November 2005, entering a bear market last month as slumping commodities dragged down the materials and energy shares that account for more than two- fifths of its value. The S&P/TSX is still trading 91 percent higher than in October 2002, when the last bull market began.

Energy, metals and agricultural commodities comprise more than half Canada's exports.

The US buys about three quarters of the total. A gauge of materials stocks slid 17 percent for its steepest intraday drop since the index's start in 1995.