The U.S. Agriculture Department this week announced it HAD found the first case of soybean rust in the mainland United States in two small plots of a research farm near Baton Rouge, Louisiana.

Soybean rust is a wind-borne disease characterized by reddish brown lesions on soybean plants as they drop their leaves. The disease can seriously erode crop yields.

Fungicides are the only short-term way to protect U.S. soybean fields. Soybean varieties resistant to the fungal disease are five to 10 years away, industry experts said.

With most of the U.S. soybean crop already harvested this year, the farm group said Bayer, Syngenta and other chemical companies have time to produce an ample supply of fungicides for 2005.

The Environmental Protection Agency said it has approved four types of fungicides in 25 states, including Louisiana, for farmers to use.

The discovery of rust in Louisiana is likely to speed up the EPA's approval of several more types of fungicides, an EPA spokeswoman said. Under federal law, states can petition the EPA requesting the emergency use of an unapproved fungicide.

"We recommend that soybean producers not panic and run out and buy a whole bunch of fungicides," said David Wright, soybean expert with the farm group.

The USDA estimated fungicides to combat the disease could add $25 an acre, or 15 percent to 20 percent, to the cost of growing soybeans. If fungicides were applied to all U.S. fields planted with soybeans in 2004, it would cost farmers a total of about $1.87 billion.