January 25, 2011

Parana Records Half of all Soybean Rust Cases in Brazil

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

During the 2009/10 growing season, the state of Mato Grosso ended up with the most cases of soybean rust followed by Goias, Rio Grande do Sul, Mato Grosso do Sul, and Parana. This growing season the ranking has changed with Parana registering 50% of all the confirmed cases of rust thus far in Brazil followed by Rio Grande do Sul, Goias, Mato Grosso do Sul, and Mato Grosso. Embrapa has confirmed 208 cases of rust in Brazil with 102 of those cases in the state of Parana.

Parana records 102 cases of soybean rust - Researchers at Embrapa feel there are several reasons why the state of Parana has the highest amount of rust cases this growing season. First of all, the winter/dry season months were not as dry as they were in central Brazil and this allowed some of the volunteer soybean plants to remain alive and serve as host plants for the rust spores. That allowed the rust spores to move into the soybean fields of Parana earlier than in other states further north where the dry season was extremely dry.

Scientists feel another source of the disease are the soybean fields right across the border in Paraguay. The Paraguayan government has not instituted a 90-day soybean free period similar to what has been instituted in Brazil, and therefore rust spores can stay viable on volunteer soybeans growing in Paraguay and then just blow across the border into Parana. Lastly, the rainfall in Parana has been very regular thus far this growing season and that has been conducive for the spread of the disease.

Researchers are recommending to the soybean producers in Parana to start spraying their fields immediately in an attempt to keep the disease out of their fields and that they need to be sure to apply enough water and chemicals to penetrate all the way through the soybean canopy in order to reach the leaves at the base of the plant where the disease starts.

Mato Grosso records 4 cases of soybean rust - Embrapa indicated that four cases of soybean rust have been confirmed in Mato Grosso and that all four cases were in the municipality of Sorriso, which is the largest soybean producing municipality in Brazil. Researchers feel there are more than four cases and it's just a matter of time before more are confirmed.

The disease has entered into the soybean fields of Mato Grosso later than normal and the late start is being accredited to the extended dry season and below normal rainfall during October to December. After the dryer start, the rainfall intensity in Mato Grosso has increased during January. During the first 20 days of January, the city of Sorriso received 227 mm of rain (9 inches), which was more than the 215 mm recorded during all of January 2010.

The most susceptible time for soybean rust is when the plants are flowering and setting pods and the increased rainfall is occurring as the soybean crop is entering that phase. As a result, researchers are expecting the number of confirmed rust cases in Mato Grosso to increase rapidly.

Four years ago, the state of Mato Grosso, in conjunction with the Mato Grosso Soybean Producers Association, set up a series of 16 mini-laboratories around the state where leaf samples could be analyzed for the presence of soybean rust. In addition to soybean rust, these labs are also equipped to identify many other types of soybean diseases as well.

During the last growing season, all the soybean fields in the state were affected by the disease and more than 600 cases of the disease was confirmed. The medium maturity soybeans were the most affected last growing season. The average soybean field in Mato Grosso received three fungicide applications last year with the hardest hit fields receiving four applications.