What was that about?...

This is how weird rumors get started.

Shares of farm equipment-maker Deere & Co. fell hard for a second straight session Thursday as investors, after driving agribusiness stocks to astronomical heights over the past several months, reversed course and launched a sell-off of companies that produce products used down on the farm.

Until the reversal, Wall Street had been treating ag-related stocks as if the sector, which is benefiting from high grain prices sparked by the ethanol boom, would remain largely immune from the economic turbulence that has pulled down some parts of the economy. But suddenly, and with no obvious triggering event, companies that serve the farm sector have lost their luster.

Of course, the overall stock market stumbled badly Thursday, with the Dow Jones industrial average falling more than 300 points, but for Deere and other farm-oriented companies such as Monsanto Co. and CNH Global NV, the damage was several times as bad. [More]

Pick your favorite conspiracy theory. I made these up myself. You try, too - with a little luck you could be on CNBC. (Call me, Maria!!):

1. Commodity index fund managers also have big agribusiness holdings, and they know they are going to lighten up soon on their heavily long position.
2. The checks from the Russians bounced.
3. Wildcat strikes are being whispered as machinery factories run full out, and UAW workers finally smell leverage.
4. Several thousand investors made simultaneous foolish decisions in the ag sector.
5. Investors are wisely monetizing their biggest profit positions.

The strange thing is nobody seems to have a plausible story, let alone a verifiable cause for the sell-off. How bad must it be when you can force TV experts to say "I don't know"?

One parting note: If the US stock market matches the plunge today in the non-MLK-celebrating world, stocks could drop 600-700 points tomorrow.

Anybody besides me gonna check how grains open this evening?