Commodity speculation spread long ago from standard products like oil and gold to anything edible and available for trade on the Chicago Futures Exchange. These days there are futures contracts for everything from wheat to oranges to pork bellies. The futures market is a traditional tool for farmers to sell their harvests ahead of time. In a futures contract, quantities, prices and delivery dates are fixed, sometimes even before crops have been planted. Futures contracts allow farmers and grain wholesalers a measure of protection against adverse weather conditions and excessive price fluctuations. They can also help a farmer plan how much to plant for a given year.

But now speculators are taking advantage of this mechanism.