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December 13, 2012

Early Onset of Soybean Rust Worries Farmers in Brazil

Farmers in Brazil continue to be worried about the early onset of soybean rust in their newly planted soybean fields. Embrapa Soja now reports that there have been five cases of rust confirmed in Parana, seven in Mato Grosso, three in Sao Paulo, and one in Santa Catarina. The disease is arriving earlier than last growing season when this number of cases was not confirmed until the end of January.

Scientists have been warning farmers to be on the outlook for the disease due to the high number of volunteer soybeans found along the sides of the highways that were infected with the disease. During periods of hot and humid weather, it is very easy for the disease to spread from these volunteer soybeans into commercial fields. Once the disease has been confirmed in a field of soybeans, farmers must initiate control measures immediately in order to keep the disease from getting out of control.

During the last two growing season, the disease was not a major factor in Brazilian soybean production. For the 2011/12 growing season there were only 265 cases of the disease confirmed in Brazil, which was very low considering that more than ten times that many cases were recorded in 2006/07 and 2008/09.

In Mato Grosso farmers are concerned because the soybean planting was spread out over a long period of time due to the irregular nature of the showers during September and October. Farmers who were lucky enough to receive rainfall in September went ahead and planted their early maturing soybeans while other farmers had to wait up to a month before they received enough moisture to plant.

If the early maturing soybeans are infected with rust when the crop is being harvested, the spores can be spread easily during the harvest process to later planted fields where the soybeans are still susceptible to the disease. With this in mind, scientists have advised farmers to continue applying fungicides until the crop is mature and not to try to economize by skipping the last application. If they do that, it could make the disease worse for neighboring fields.

The disease first arrived in Brazil in 2001and since then has cost Brazilian farmers billions of dollars in lost production and control measures. Embrapa has reported that in 2009/10 control measures alone cost US$ 2 billion and that does not include lost productivity. Farmers can control the disease, but that cannot be achieved without multiple fungicide applications. In areas where the disease is most intense, generally three fungicide applications are required to keep the disease under control.