Most agricultural chemical companies, such as BASF, expect Asian soybean rust to show up in the near future in the United States. If and when it does, preventive fungicides should play a pivotal role in farmers' efforts to manage the windblown disease.

Markus Heldt, BASF group vice president for agricultural products in Latin America, said rust disease “has transformed our business model in Brazil,” where farmers have been fighting the disease for several years.

In South America, the BASF fungicide, F500, has emerged as one of the preferred fungicides for Brazilian soybean farmers, after the application morphed from what was initially designated to boost winter cereals production.

Heldt said that since 2001, when Asian rust first emerged in Paraguay and then led to billions of dollars in soybean yield losses, F500 — used as a preventive treatment — has protected more than 40 million acres.

Also, according to Heldt's estimates, average yield levels in the late 1990s in Brazil were about 35 bushels per acre, but increased to 42 bushels per acre in 2004, thanks, in part, to fungicide applications.

He noted that on average farmers are now spraying fungicide — depending on disease pressures, varieties and climatic conditions — one and a half to two times per season.