September 19, 2014
Brazilian Farmers Average 3 Sprays for Rust at US$ 14 per/acre/app
Brazilian farmers are now actively planting their 2014/15 soybean crop in the states where the 90-day soybean free period ended on September 15th. The 90-day prohibition on any live soybean plants was put in place in the mid-2000s as a way to slow the spread of the disease from one growing season to the next. Scientists and farmers alike in Brazil credit this prohibition with delaying the introduction of the disease during each new growing season.
Soybean rust was first discovered in Brazil in 2001 and scientists from Embrapa estimate that the disease costs Brazilian farmers approximately US$ 2 billion per year in a combination of chemical costs and lost production.
During the 2013/14 growing season an average of approximately three fungicide applications were made on the soybean fields in Brazil at a cost of US$ 35 per hectare per application or approximately US$ 14 per acre per application. The fungicides used to combat the disease are contact fungicides which means they must be reapplied as new foliage emerges.
Scientists have advised farmers that the best way to avoid excessive losses from rust is to plant early maturing soybeans as early as possible in order to reduce the time that the crop is exposed to the disease. Before the 90-day prohibition was put in place, soybean rust was being found in Brazilian soybean fields as early as late October or early November. Since the prohibition has been implemented, the first cases of rust now generally start to appear in December and then increase rapidly in January.
The increased incidences of rust in January are associated with the increasing amount of rainfall that occurs during December and January. Therefore, if an early maturing soybean variety (95 day maturity) is planted before the end of September, the crop could be approaching maturity before the disease becomes a major concern, thus saving on control costs.
Over the years Brazilian scientists have noticed that the fungicides used to combat the disease have been losing some of their effectiveness due to the disease developing resistance, which is a natural occurrence. Scientists advise farmers to monitor the effectiveness of their fungicides and to apply the most effective fungicides on their later maturing soybeans in order to minimize losses as much as possible. They also advise farmers to plant soybean varieties that are more resistant to the disease and to rotate their fungicides in order to delay as much as possible the development of resistant rust spores.