Soybean rust is a new threat to soybean production in the U.S. The disease was first reported in 2004 and was a problem in the southern production areas in the U.S. in 2005 and 2006. In 2007, the disease was found for the first time in Oklahoma.

In the 1970's and early 1980's benzimidazole fungicides were tested. Generally, yield responses were not sufficient to offset the cost of application. In trials at two locations in 2004-2006, single applications of a fungicide at the R3 growth stage did not increase yields of dryland or irrigated soybeans. None of these trials had pressure from soybean rust or frogeye leaf spot.

In 2007, early maturing (MG3) and full-season (MG5)...