Overwintering soybean rust and the big question

Don Hershman, University of Kentucky plant pathologist, addresses the question:

Will the fact that Asian soybean rust (ASR) overwintered in several Southern states make any difference in how the disease moves in 2009?

Hershman, quoted at length in an article distributed by UK this week, looks at all the factors and arrives at the only plausible answer:

Who knows?

Those aren't his exact words, just a quick summation.

This isn't to deride Hershman, a respected plant pathologist. The article does illustrate that people have generally quit guessing about what will finally happen with ASR, if anything much at all. It does have potential to cause destructive crop loss, as witnessed in South America and other places where it's run rampant. One veteran plant pathologist, Billy Moore of Mississippi, said almost from the beginning that maybe 2 years out of 10 could turn into a bad year for ASR.

Why haven't we had one of those years yet? Theories vary, having to do with weather movement, regional droughts, cropping patterns, heavy spraying in Dixie for other diseases and maybe the influence of fairies. (Okay, I made up that last one.)

Botton line: it's never emerged as the expected threat here. Certainly, preventive ASR treatments were needed and were made in recent years, mainly in the lower South. But nothing like the widescale applications once predicted. Chemical companies started betting 5 years ago that nearly every acre of beans in the U.S. would have to be sprayed at least once with a fungicide. The idea was that this Godzilla-like force would push up the Mississippi Valley and bully its way into all those states that start with the letter "I". Factories geared up to turn out fungicides. Web sites sprang to life with all manner of predictive models and chatter. Vast amounts of forestry resources were channeled into the production of paper to carry all the promotional pieces that touted one fungicide over another.

And the demand, so far, has not come to pass. ASR continues to show up too late to matter. It's a factor in areas where an alligator can spend the winter, but not much north of there.

Still, there are plenty of reasons to spray fungicides on soybeans.

The air teems with spores that can reduce yields. On a localized basis, plenty of farmers have lost small fortunes to common pathogens that, compared to ASR, have caused more net damage but need better press agents. The decisions to treat these maladies are typically made on a field-by-field basis without benefit of early-warning systems. Eventually, we'll be to that point with ASR, too.

Hershman's observations are worth reading. He's not saying to let your guard down, nor is he telling anybody to panic.

Like other top plant pathologists dealing with ASR (or the lack of it), I figure that he's learning as he goes. Maybe there will be new lessons this year.

Who knows?

-- Owen Taylor