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Corn+Soybean Digest

In-Field Rust Detector

At first, the microscopic specs are invisible to the naked eye. And by the time Asian soybean rust is easily detectable, controlling the aggressive disease is more challenging.

Rust infestations begin stealthily and mimic several other soybean diseases. That's why the United Soybean Board (USB) and the Iowa Soybean Promotion Board (ISPB) are funding a research project led by Anne Dorrance, an Ohio State University (OSU) soybean pathologist. Their goal: to develop a quick, in-field test to help growers confirm the presence of Asian soybean rust in their fields.

According to David Wright, director of the North Central Soybean Research Program, USB, ISPB and OSU are working with the Department of the Navy to develop the test. He says the Navy has a proven track record of successfully developing this type of test.

Dorrance says the test will be a small handheld device. The grower will smash up soybean leaves and deposit the extract from the crushed leaves on a test strip. If the strip turns color, rust is present in the field. If not, there is no rust.

Currently, Dorrance has been working to develop antibodies that detect rust, and the first indications are that those efforts have been successful. She says the antibodies are now being tested to make sure they are specific to Asian soybean rust and don't cross-react with other diseases.

“This will be good technology for soybean producers who want to refine their management programs,” says Wright. “Fungicides only have so many days of residual activity. If a Midwestern grower sprays fungicide June 6 and the spores are in Kentucky, they've probably lost the benefit of the entire application. This test would provide growers with much better means of managing soybean rust.”

Dorrance adds, “Flowering to R6 encompass much different time spans from region to region. If we can delay the first application until there are a few lesions in a field or a neighboring field, growers will be able to maximize their fungicide applications.”

Accuracy is also a must

“If the test isn't accurate, we won't move forward. We'll have to go back and look for another alternative,” says Dorrance. “This test must be specific to Asian soybean rust and must be able to detect very early lesions.”

Both Dorrance and Wright agree that keeping the cost of the test within reason is crucial. “Compared to the misapplication of fungicides at $12-15/acre, we're hoping the cost of the test will be considered negligible,” says Wright.

The goal is to be able to offer the test to growers in 2006. As Dorrance says, “anything can happen in science,” but she is optimistic that a test will be available next year.

In-Field Test Available This Year

A private company, EnviroLogix, Inc., Portland, ME, has announced that it is in the final stages of developing a quick test for Asian soybean rust.

According to the company, its test is called QuickStix, a 10-minute test strip for in-field testing. EnviroLogix anticipates that the QuickStix test will be available for this year's planting season.

Dean Layton, vice president of marketing and sales for EnviroLogix, says the company is refining the protocol for the test, but he expects that the test will be similar to its ELISA plate format test already available for lab use. Growers will mix leaf tissue with a liquid in a vial and drop in a test strip.

The sensitivity will approach that of the ELISA test, which he says can detect spores even before spots or discoloration appear on the soybean leaf, and which do not cross-react with other soy fungal, bacterial or viral diseases. For more information, visit and go to the section on plant pathogens.

Dorrance wouldn't comment on the EnviroLogix test, but Wright says it's a positive that there will be more than one test on the market.

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