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November 19, 2018

Soybean Rust could be bigger Problem this Year in Brazil

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

Researchers in Brazil are concerned that the record early soybean planting could also result in higher costs for controlling soybean rust.

The disease spreads more easily during years when there is abundant rainfall and warm temperatures, which has been the case in southern Brazil. Rainfall in southern Brazil during September and October was above normal. Soybean planting in Parana started immediately after the soybean-free period ended on September 10th. This year, the concern is that the soybean planting was not uniform and that the early planted soybeans could harbor the disease which could then infect soybeans that are still being planted.

The continued spread of the disease will depend on the weather of course. If the weather remains wetter than normal, that would facilitate soybean growth as well as the spread of the disease. If the weather would turn dryer than normal, that would hinder the spread of the disease, but it would also be detrimental to soybean development.

Last year it was just the opposite because dry weather during September and early October delayed the soybean planting, which then delayed the onset of soybean rust.

Embrapa reported last week that there have been 17 confirmed cases of soybean rust in commercial soybean fields in Brazil. The state of Parana had the most with 13 followed by Sao Paulo with 3 and Santa Catarina with 1. What worries researchers is that this is the earliest that soybean rust has ever been confirmed in the state of Parana. Last year at this time, Brazil had confirmed 3 cases of soybean rust in commercial fields.

Soybean rust is the most expensive crop disease in Brazil. The cost of controlling the disease averages about 2 billion dollars per year. The majority of the costs come from fungicide applications, but there are also costs from reduced productivity as well.

Researchers are advising farmers to remain alert and be prepared to apply fungicides as soon as the first symptoms appear and not to schedule their spraying according to the "calendar date." The disease is very aggressive and the disease cycle is very fast, so farmers need to attack the disease as early as possible.