What does soybean rust look like?
The most common symptom of infection of Phakopsora pachyrhizi is gray to tan or reddish-brown lesions or spots, with raised pustules within the lesion. Premature defoliation occurs as the disease progresses.

It is easy to confuse the symptoms of soybean rust with symptoms of other foliar soybean diseases like brown spot, bacterial pustule and bacterial blight, especially in the early stages of the disease.

Can I see soybean rust in the field?
Identification of the disease in the field at low incidence with less than 10 percent of the leaves infected is very difficult. To improve chances of identifying low levels of soybean rust, leaf samples must be incubated and observed in the laboratory using a microscope, not observed for lesions and pustules in the field. If soybean rust has become severe enough in a field, it may be identified by examining the underside of leaves and looking for raised pustules using a hand lens.

How can I gauge the risk of soybean rust getting to Iowa? 
The national Integrated Pest Management Pest Information Platform for Extension and Education (ipmPIPE) web page helps soybean farmers track the movement of soybean rust and gauge the risk of soybean rust entering Iowa. Another useful tool is the Drought Monitor web site, which indicates what parts of the United States are experiencing rain shortages. These two resources can provide information on where soybean rust is currently and the weather conditions conducive for rapid spread – soybean rust thrives in rainy conditions. Iowa State scientists will continue to monitor the risk of soybean rust and make appropriate announcements when those risks are elevated.

What are ideal weather conditions for soybean rust development?
Soybean rust thrives in cool, moist weather. In 2004, the frequent rain, cloudy and cooler weather was an example of the ideal conditions. Any deviation from those conditions will slow the development of the disease. The disease will progress slower in warmer weather and may not develop at all during dryer periods.

Will increased hurricane activity spread rust more?
Hurricane Ivan is thought to have brought soybean rust to the United States. Hurricanes are now associated with the movement of soybean rust. The soybean rust pathogen needs a susceptible host, such as the soybean plant, and faborable environmental conditions for disease development. If P. pachyrhizi spores are transferred due to hurricane activity, they still need to land on soybean plants at a susceptible growth stage with periods of extended leaf wetness. It is possible that one particular hurricane will disperse rust spores at a time and to a place that favors disease development. If rust spores are carried to an area that is hot and dry, the disease may not develop.

If soybean rust spores are found in Iowa, does that mean that the disease is here as well?
Each year there is a nationwide effort to track the movement of soybean rust spores. To identify spores rain is filtered and tested for the pathogen’s DNA. If soybean rust spores are found in Iowa, it does not necessarily mean the disease is present but is an indicator that soybean rust may follow. Soybean rust spores are very sensitive to solar radiation, so spores moving in little to no cloud cover may not be alive when they arrive. Because spores are sensitive to environment (mostly light), movement of viable spores is limited to specific situations, such as heavy cloud cover.

Does soybean rust affect any other crop in Iowa?
More than 90 other plant species have been reported to be susceptible to the soybean rust pathogen. Of these susceptible hosts, 20 species are found in the southern United States, according the Plant Health Initiative (http://www.planthealth.info/rust_basics.htm) website.  These plants include kudzu, jicama (yam bean), coral bean, yellow sweet clover, vetch, medic, lupine, along with green, kidney, lima and butter beans. Some of these are grown in Iowa. The good news about alternate hosts is that corn and other grain crops are not hosts to the soybean rust pathogen.

Will the soybean rust pathogen survive the winter in northern climates?
No, the pathogen needs living tissue to survive and a hard frost will kill the foliar tissue of susceptible plants, including alternative host species. Areas that are likely to support year-round occurrence of P. pachyrhizi are the very southernmost areas of the United States and countries to the south where freezing temperatures are rare. The presence of kudzu, jicama and other alternative hosts in these southern regions allow survival of the soybean rust fungus.