Iowa State University researchers have developed a way to use satellite images to find Asian soybean rust.

"What we did on the ground 10-15 years ago, we can do now with satellites," says Forrest Nutter, professor of plant pathology.

Using remote sensing, Global Positioning System and Geographical Information System technologies, scientists can measure the green leaf area of soybeans to detect and identify diseases down to the area of a square meter, about 1.2 square yards.

"Plant pathogens and pests impact the green leaf area index of crop canopies in different ways and those changes can be detected and quantified using remote sensing," Nutter says.

The footprints of early soybean rust infection are oval-shaped. The way it spreads over time in a field helps identify it from other diseases.

Nutter envisions the technology being used to narrow the search for soybean rust or other diseases. Plant disease detection using satellites would provide the GPS coordinates for spotters on the ground to pinpoint locations to collect disease diagnoses field samples. The samples would then be taken in for laboratory tests to confirm the identity of the plant disease at that location.

Tests conducted last year in South Africa demonstrated the technology. Nutter has been working on the project with plant pathologist Neil van Rij of Cedara, South Africa; John Basart, Iowa State engineering professor; and Khalil Ahmad, engineering graduate student.

Nutter says USDA and the Department of Homeland Security are interested in using the technology to alert officials to a soybean rust infection during the crop season. Being able to monitor the movement of soybean rust could help reduce the impact of the devastating disease.

The Department of Defense and Army have helped fund the research in the hope that it could be used to determine a deliberate introduction of a plant pathogen.

The use of commercial satellite services has been a limiting factor for this technology, Nutter says. It can take two weeks to two months to receive images after ordering. Basart is helping the group develop methods of capturing their own images using aircraft and balloons that would reduce the time to obtain images to one or two days.

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