Asian rust's foray into the major soybean growing regions of Argentina and Uruguay this year might be a harbinger of things to come for US farmers this summer.

Laura Karlen of Ag Advisory, an Algona, Iowa, crop consulting firm, returned in early April after visiting Argentina and Uruguay. "They were going through many of the same things (before their growing season) that we're going through now," she says.

As in the US, Asian rust had been detected in a handful of spots in both of the countries before planting. Asian rust then moved in during the growing season and blanketed Uruguay and central Argentina, where much of that nation's soybean production occurs. Excellent preparation by farmers, agronomists, plant pathologists and others has helped them weather Asian rust.

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"When it started popping up, they were so well prepared that they caught it early on and treated it," says Karlen.

Farmers in Uruguay incorporated Asian rust monitoring into an already rigorous soybean scouting program that existed for other pests. In Argentina, a rapid detection system was established where farmers send leaf samples in plastic bags also containing water to diagnostic labs. The moisture aids detection by speeding proliferation of rust in infected leaves.

"It's important to keep in mind we can't use them as an exact model for what may happen here," says Karlen. "They have a different climate and wind patterns. But we can definitely learn from them."

The growing climate of these countries more closely resembles the US than does the steamy tropical environment of Brazil. "It's more like Arkansas and Missouri, where frost occurs in the winter," says Karlen.

Similarities also include spore arrival via wind. Last fall, hurricanes blew Asian rust spores northward into the US. It was the opposite situation in Argentina and Uruguay, where northern winds blew spores from the Asian rust hotbed of Brazil.

Once Asian rust was initially detected in Uruguay and central Argentina, it quickly surfaced all over. Soybeans double-cropped after wheat in Uruguay were the most prone to infection, as they were in the R4 (full pod) and R5 (beginning seed) stages. These fields were more likely to be infected and treated than early-planted soybeans that were further along in the R6 (full seed) stage.

For the most part, farmers are successfully battling Asian rust with a strategy of scouting and spraying with fungicides immediately after leaf pustules surface in a field, says Karlen.

In both nations, farmers treat infected fields with curative fungicides or a mixture of curative and preventive fungicides. These mixtures include fungicides from both the triazole and strobilurin families, which also are approved for use in the US.

"They seem to be the popular trend in Brazil, and that's following through in Argentina and Uruguay," says Michael McNeill, Ag Advisory president.

Few market surprises

Grain market watchers have closely watched developments in South America like these. In February, concern over deceased South American soybean yields helped rally the market. It's possible rust rallies may predominate.

However, one factor that may reduce market surprises is the educational effort that's been done among US farmers in recent months.

"Everyone knows about rust," says Ron Mortensen, president of Advantage Ag Strategies, Fort Dodge, Iowa. "It is not a surprise."

Rallies also will hinge on if and how quickly Asian rust moves northward and how farmers respond.

"It depends on how everyone responds when we're in the trenches," adds Mortensen. "Two years ago, Asian rust would have been a big surprise and caused a big panic. That probably isn't the case now."

StopSoybeanRust.com is a Web site with news, information and resources about Asian soybean rust, created by the Greenbook, Dealer & Applicator magazine and Successful Farming magazine. It is sponsored by Bayer CropScience US. Cooperating partners include the United Soybean Board and the Crop Advisor Institute.