Iowa Farmer Today
06-17-06
Tests offer rapid rust ID
By Tim Hoskins, Iowa Farmer Today
ALGONA -- Iowa farmers have more options to test for Asian soybean rust.
Two private entities offer three tests for the pathogen, which will provide results
in 10 minutes to two hours. The private tests add to the tests conducted by
Extension and the USDA.
Michael McNeill, a crop consultant with AgAdvisory in Kossuth County has set up
a a private diagnostic field lab.
“We are a field lab. We want to be as accurate as possible, as fast as possible,”
he says.
McNeill, who had the lab operating last year, uses a microscope to look for
soybean rust, comparing with photos what he sees.
He says after working with rust for a number of years, including traveling to
Brazil, he is able to visually identify soybean rust.
Other private tests for Asian rust have been developed by EnviroLogix in
Portland, Maine.
The company offers a 10-minute strip test and a two-hour test. Both are antibody
tests that reacts to presence of rust.
“We have been able to detect soybean rust before symptoms appeared,” says
Dean Layton, vice president of marketing and sales for EnviroLogix.
The 10-minute strip test can be performed in a field. After taking a leaf sample
and adding a buffer solution, the strip is inserted into the solution, which changes
color, depending on the presence of rust.
X.B. Yang, Iowa State University plant pathologist, says chemical tests are
more reliable than visual observation.
However, he says both tests are not as reliable as USDA molecular testing for
the disease, which is used for official confirmation.
ISU’s fast-track system uses a network of first detectors and Extension to forward
a suspected soybean sample to the USDA for testing.
McNeill is not able to officially confirm soybean rust. The official identification is
done by the USDA.
However, he compares that to knowing a person by recognizing their voice and
what they look like and asking for a DNA test to confirm it is the correct person.
The cost to test a sample is $25. Last year, he partnered with Bayer CropScience
to offer free testing.
For treatment options, farmers are referred to their crop consultant and Extension
staff.
“We are strictly a diagnostic lab,” he says.
The cost of EnviroLogix’s strip is $4 per strip.
Layton says they have replicated the validation studies on the strip test and are
working with rust experts and Extension personnel to further validate the test.
The 10-minute strip test should be available for purchase within a month or two.
The two-hour test is now available. With this test, plates of up to 96 samples are
sent to a lab.
The cost of the plate for the two-hour test is $295.
Layton says the two-hour test is more sensitive than the filter strip test. However,
the filter strip test does not require any lab set up or lab training.
“I think the strip tests will be a more efficient tool for field scouts,” he says.