Crops' rally stumbled over a stronger dollar and weaker oil, plus improved forecasts for US weather, reducing the prospect of a significant downgrade to estimates for bumper corn and soybean harvests.
Corn led the retreat, tumbling 5.0% to $3.78 a bushel in Chicago for December delivery, wiping out all but a handful last week's gains.
But investors weren't in much of a buying mood across the farm commodities spectrum, with most softs – bar orange juice – also out of favour.
The backdrop was set by a rush by investors back to the safety of the dollar, which rebounded strongly from 14-month lows, so making US exports, such as crops, less competitive.
Against the euro, the greenback strengthened from above $1.50 to $1.4849, while gaining 1.4% against the Canadian dollar.
Several reasons were raised for the dollar's revival, including the prospect of an end to tax credits which have supported the US housing markets to reports that American authorities are to unveil proposals to facilitate government takeovers of failing financial institutions.
The flight to safety was also evident in falling equity markets, with the Dow Jones Industrial average left well below the 10,000 mark.
And oil proved surprising weak against the selling spree, shooting back 2.4% to $78.57 a barrel, a negative sign for crops, many of which are used in making biofuels.
With the US also facing the prospect of better harvesting conditions next week, the scene was set for a sell-off which materialised with gusto.
Wheat for December lost 3.8% to $5.27 a bushel, with November soybeans down 1.9% at $9.86 ½ a bushel.
In quieter days, the market might have take some cheer at official data showing US weekly export inspections for soybeans at a robust 43.8m bushels. (Corn's figure of 24m bushels and wheat's 14.3m bushels came in below traders' forecasts.)
But the weather and the dollar left little scope for bulls. Indeed, funds were estimated sellers of 13,000 corn contracts and 6,000 wheat lots in Chicago.
Among soft commodities too, fundamental news appeared to hold little sway – although a report that Ivory Coast's marketing arm may revise bean arrivals data upwards will have done little to help the mood.
The revision could add 50,000 tonnes to forecasts for cocoa supplies from Ivory Coast, the world's biggest producer of the bean.
Cocoa ended down $11 at $3,354 a tonne in New York for December delivery. London did better, adding £1 to £2,208 a tonne, helped by weaker sterling.
Continued strength, prompted by US forecasts of a drop in Florida's citrus crop in 2009-10, was credited for a 0.75 cent rise to $1.154 a pound in January orange juice.