March 22, 2011

Soybean Rust not a Major Concern in Mato Grosso in 2010/11

Author: Michael Cordonnier/Soybean & Corn Advisor, Inc.

Soybean farmers in Mato Grosso have registered 92% fewer cases of soybean rust during the current growing season compared to 2009/10. Embrapa is confirming that 707 cases of soybean rust have been confirmed in Brazil, but only 50 of those cases were confirmed in Mato Grosso. The state of Parana registered the most cases of soybean rust this growing season with 291.

Most researchers from Embrapa believe the reduced incidence of the disease is the result of the prolonged dry season in 2010 that delayed the onset of the rains until mid to late October. Soybean rust spores cannot survive for more than about sixty days without a host plant and the extended dry season helped to eliminate many of the potential host plants. The dryer than normal weather during November and December is also believed to help restrict the early spread of the disease in the state. Even though wet weather moved into the state late in the growing season, the rains probably came too late as far as the spread of soybean rust is concerned.

Soybean rust is not thought to have caused significant yield losses in Brazil this year, but it continues to increase the cost of producing soybeans in the state. Soybean farmers in the state applied on average 2 or 3 fungicide applications in order to keep the disease under control. Each application costs approximately R$ 30 per hectare or the equivalent of approximately US$ 7.50 per acre. With an average of 2 or 3 applications per year, farmers in the state are spending R$ 90 per hectare or US$ 22 per acre to control the disease. In the state of Goias, researchers estimate that soybean rust reduced yields an average of 1.3 sacks of soybeans per hectare or approximately 1.1 bu/ac.

Farmers realize the severity of the disease and the most successful farmers are proactive in combating the disease. Researchers recommend that the first fungicide application be made at the R1 growth phase or as soon as the soybeans start to flower. Successive applications are made every 25 to 35 days depending on the frequency of the rains.

Embrapa crop researchers have had some success in breeding improved tolerance for the disease and chemical companies such as Bayer Crop Science have developed more effective fungicides to control the disease.