November 23, 2016
First Cases of Rust Confirmed on Commercial Soybeans in Brazil
Embrapa reported last week that the first case of soybean rust in commercial soybeans in Brazil was confirmed on November 15th in the state of Sao Paulo. The infected soybeans were planted in late September. A second case was confirmed in the state of Parana on November 18th. In 2015, the first case of soybean rust in commercial soybeans was confirmed on November 6th, also in the state of Sao Paulo.
Scientists in Brazil are not too concerned about soybean rust, at least not yet, but they are advising farmers in the region to start monitoring their more advanced soybean fields and to take leaf samples if they suspect rust is present in their fields. Rust usually starts at the bottom of the soybean plant where the relative humidity is higher, especially after the canopy has closed. That is why it is important that the fungicides penetrate the leaf canopy down to the base of the plant. The fungicides that are used to control rust are contact fungicides, which means that repeat treatments are needed as new leaves are exposed to the disease.
The total number of rust cases in Brazil is unknown at this time because Embrapa's web site that tracks the disease is being redesigned and it is not completely functioning. What we can say is that there were 69 cases last year at this time and the 5-year average is 23 confirmed cases.