Fears of lower demands for pork due to swine flu outbreaks caused soybean futures to slump the most in more than two months on Monday. Maize and wheat were also pulled into the scares.
Several US states have suspended imports of all meat from Mexico as well as Russia and other countries may follow soon, according to analysts.
Soybeans for July delivery dropped as much as 5.7% to $9.7525 a bushel in electronic trading on the Chicago Board of Trade, the biggest loss since Feb. 17. It was last down 21.25 cents, or 2.1%, at $10.1275.
The contract had been on the rise since early March and had climbed above $10.70 on April 17, the highest since late September, or up nearly 25% from March low.
Maize also down
Meanwhile, maize for July delivery lost as much as 4.1% to $3.70 a bushel, the lowest in a week. The contract was last down 5.25 cents, or 1.4%, at $3.805.
July wheat fell 13.5 cents, or 2.5%, to $5.2975.
Swine flu alert
In Mexico, an estimated 1,614 people have contracted swine flu and 103 people have died.
Dr Margaret Chan, Director-General of the world Health Organisation, has determined that the current events constitute a public health emergency of international concern, under the Regulations.
The Director-General has raised the level of influenza pandemic alert from the current phase 3 to phase 4.
The change to a higher phase of pandemic alert indicates that the likelihood of a pandemic has increased, but not that a pandemic is inevitable.