Risk of soybean rust for 2008

Even though soybean rust was found in Iowa in 2007, the pathogen cannot survive in Iowa. The pathogen can only survive on living plant tissue of susceptible plants. Likely overwintering sites are in Florida and Texas on kudzu and in Central America on legumes, such as jicama and soybean. This means the risk of rust getting to Iowa in 2008 is the same as it was at the beginning of past years. For rust to get to Iowa, it will need to successfully overwinter somewhere in the South and retrace the path it traveled in 2007.

What happens if soybean rust gets to Iowa earlier in the season?

There are no resistant cultivars available for soybean rust and there may not be for several years. The main management strategy is well-timed foliar fungicide applications. In 2007, several fungicides that received Section 18 labels for soybean rust in 2004 were granted Section 3 labels for use on soybean. Also, a few additional Section 18 fungicides were approved by the EPA in 2007. Section 18 labels for Folicur® and Headline® SBR expired in November, so they will need to be renewed if these fungicides will be available in Iowa in 2008. Below are two lists of fungicides available (or potentially available) for soybean rust.

Table 1. Available fungicides for management of soybean rust in Iowa.

Table 2. Fungicides that may be available for management of soybean rust pending a decision by the EPA.

*Section 18 label may be extended.

Daren Mueller is an extension plant pathologist with the Iowa State University Corn and Soybean Initiative and the Pest Management and the Environment Program.