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Asian Soybean Rust Strategies
By Jim Gleason, Regional Vice President, St. John, Kan
With the discovery of soybean rust in Louisiana in November, U. S. soybean farmers are faced
with the reality of contending with this disease next year.
Asian soybean rust will overwinter on plants in the southern areas where it was first identified, but it
will not be able to survive through the winter in the more northern parts of the United States. For it
to infect the bean crop, the spores will have to be windblown from the south by next summer. When the
disease spores move up, the right environmental conditions will be needed to infect the bean crop. The
disease will need warm temperatures and the bean leaves need to stay wet for 6 to 8 hours after infection
for the disease to get started.
USDA is predicting less than a 50% chance of having a rust outbreak in Kansas for next year. Prevailing
winds from the south or southwest during the summer should blow the rust away from us. The lower humidity
levels we have during the summer, compared to the Corn Belt, lowers our chances of having soybean rust
for 2005.
We don't want to assume that we are completely safe from this problem. This is a very aggressive organism
and can develop into a huge problem in a matter of days. We need to have a strategy in mind if it does
show up. Early detection is the first step.
If rust is found in a field, be prepared to treat with a fungicide. Several chemicals are currently
labeled and more are expected to be approved by spring. The cost, usually between $15 and $20 per acre,
will easily pay for itself when rust is found. In South America, Asian soybean rust has caused 80% to
100% yield loss when left untreated.
The surest way to avoid rust is to not plant soybeans next season. However, with the odds of not
having a problem in our favor, we may be able to grow them more profitably in Kansas than in other
parts of the country.
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