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November 29, 2012

Wet Weather Increasing Risk of Soybean Rust in Central Brazil

As farmers in central Brazil complete the planting of the 2012/13 soybean crop, their attention is now directed to monitoring the newly planted fields for the presence of soybean rust. Soybean plants become more vulnerable to rust infection after they start to flower and during periods of prolonged wetness. Both of those conditions are expected to be present over the next two weeks in parts of Mato Grosso, which is the leading soybean producing state in Brazil.

The Brazilian Embrapa research service has confirmed four cases of rust in Mato Grosso and all four cases were on volunteer soybeans growing along the side of the highways. One case each was confirmed in the municipalities of Sapezal and Campo Novo do Parecis, which are located in western Mato Grosso, Lucas do Rio Verde located in central Mato Grosso and Alto Araguaia located in for southeastern Mato Grosso. With the disease already infecting soybeans along the side of the highways, it'Ns only a matter of time before it moves into commercial soybean fields.

Farmers in the western municipalities are especially concerned because the weather forecast for these two municipalities is for as much as 200 mm of rainfall (8 inches) over the next fifteen days. If that much rainfall materializes, it would be ideal for the spread of the rust spores into the newly planted soybean fields. Scientists are advising farmers to be prepared to make their first fungicide application as soon as the disease is confirmed in commercial soybeans in their region.

Soybean rust was first identified in Japan in 1903 and it is a common disease in Chinese soybean fields. The disease made its way to Brazil during the 200/01 growing season after first being identified in neighboring Paraguay. It is suspected that the disease was present in soybean hulls that were used as packing material for merchandise shipped from China to Paraguay, but that was never confirmed. In the intervening years, it has cost Brazilian farmers billions of dollars in increased control costs and lost production. If left unchecked, the disease can cause yield losses of up to 80%.