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March 2, 2015

Rio Grande do Sul Registers Most Cases of Soybean Rust in Brazil

The biggest problem for soybean producers in northwestern Rio Grande do Sul this growing season has been soybean rust. Normally, their main concern is a lack of rainfall during January, but this year, it was just the opposite. In the municipality of Santa Rosa in northwestern Rio Grande do Sul, which is considered the birthplace of soybean production in Brazil, the January rainfall totaled 300 mm (12 inches), which was the most rainfall in January in 30 years.

According to the director of the Copermil Cooperative, Sergio Schneider, the hot and wet weather during January was ideal for the spread of the disease. The cooperative has 5,000 members in 11 municipalities in the northwestern region of the state and the members averaged four applications of fungicides this growing season to control rust. Some farmers tried to save money by cutting back on fungicide applications only to see their soybean yields decline.

Those that sprayed only twice are looking at a decline of at least 5 sacks per hectare (4.3 bu/ac) due to the disease. Farmers who applied five applications are looking at very good yields in the range of 50 sacks per hectare or 43.5 bu/ac. Long term soybean yields in Rio Grande do Sul are some of the lowest in Brazil due to periodic droughts, so a yield of 50 sacks per hectare is very good. The soybean harvest in Rio Grande do Sul will start in mid-March.

Embrapa is now reporting 320 cases of soybean rust in Brazil. The state of Rio Grande do Sul leads with 110 cases followed by Parana with 88 cases, Goias with 40, Mato Grosso with 31, Mato Grosso do Sul with 19, Sao Paulo with 21, Santa Catarina with 11, and Minas Gerais with 1. The nine-year average for this date is 1,147, but if you look at just the last four years, the average is 420 cases. The worst year was the 2006/07 growing season with 2,129 cases and the best year was the 2011/12 growing season with 256 confirmed cases.

The only two states where rust has been a concern this year are Rio Grande do Sul with 110 cases and Parana with 88 cases. Last week there were 88 fewer cases than the four-year average and this week there are 100 cases fewer than the four-year average. If you look at the nine years for which data is available, last week the number of cases (280) was 27% of the nine-year average (1,023) and this week the number of cases (320) is also 27% of the nine-year average (1,147).

Outside of southern Brazil, soybean rust has not been a major concern for Brazilian farmers. The way it looks now, the 2014/15 growing season will end up with the third fewest cases of soybean rust in Brazil.