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January 15, 2016

Soy Rust Control must be 85% Effective or Farmers will lose Money

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

Farmers in the state of Parana in southern Brazil continue to be worried about the high level of soybean rust infestation in their fields. Currently, Embrapa is reporting 121 confirmed cases of rust in the state or 47% of all the rust cases reported in Brazil (256). Persistent wet weather for the last several months has resulted in ideal conditions for the spread of the disease.

In recent years, these has been more evidence that the disease is quickly developing resistance to various fungicides resulting in less effective control of the disease. Since the disease became important in Brazil during the 2002/03 growing season, farmers have experimented with various fungicides in an effort to control the disease. Some of these fungicides were very effective and are used to this day, while others were less effective and were used for only a short period of time. The problem now is that the same chemicals have been used for a long period of time allowing the disease to develop resistance. Brazilian scientists estimate that if the fungicide is less than 85% effective in controlling the disease, farmers will actually lose money on their fungicide application through a combination of lower yields and higher costs.

As recently reported in Noticias Agricolas, agronomist Erlie Melo Reis from OR Sementes, stated that over the past five growing season, the effectiveness of various fungicides has been on the decline due to the development of resistance by the disease.

According to Reis, if all the costs of controlling the disease are compared to the a price of soybeans at R$ 80.00 per sack (approximately US$ 9.10 per bushel using an exchange rate of 4 Brazilian reals per dollar), if the disease control is less than 85% effective, a farmer will actually lose money on his fungicide applications because the added costs won't be compensated for by increased yields.

Unfortunately, there are no new fungicides that will be coming on the market for at least the next five years, so farmers are being urged to make better use of the existing fungicides. One important thing they can do is to rotate their fungicides and to use fungicides with different modes of action in order to slow down the development of further resistance. Farmers might even consider combining fungicides in the same application to get better control.

Since soybean rust was found in Brazil during the 2000/01 growing season, it has costs Brazilian farmers billions of dollars in lost yields and added costs.