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December 28, 2011

White Mold and Soybean Rust Worry Farmers in Central Brazil

While the majority of the news in recent days has been about the dry weather in southern Brazil, farmers in Goias and Minas Gerais in central Brazil have the opposite problem - too much rainy and cloudy weather. Their concern is that the wet weather could increase disease pressure on the soybean crop. For the last several weeks a frontal system has been sitting over the region with nearly constant cloudy conditions. The concern is that the lack of sunshine and dryer conditions will promote the growth and spread of fungal diseases.

White mold has already been identified in the soybean fields of Goias and continued wet weather could help the spread of the disease. The other disease they are worried about is soybean rust. Thus far, there have only been three cases of rust reported in the state of Goias, but that could change quickly.

The problem with wet weather and the control of rust is the fact that contact fungicides used to keep the disease in check, which means they must be reapplied at definite intervals, usually 20 to 30 days apart. During periods of rainy weather, the intervals between applications need to be reduced to in some cases as little as 15 days apart. The reduced interval is due to the heavy rains washing off the fungicide. If a farmer cannot apply the fungicide at the correct time due to wet conditions, the disease could get out of control resulting in yield losses.

At the current time, rust is not a major concern in Brazil with only 15 cases of the disease being reported in Brazil.