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January 12, 2012

Increased Cases of Rust in Mato Grosso Worries Producers

While farmers in southern Brazil continue to be very worried about the prolonged drought and its impact on their soybean and corn production, farmers in Mato Grosso and central Brazil are starting to be concerned about the presence of soybean rust in their fields. Embrapa has confirmed 38 cases of rust in Brazil with 14 of those cases registered in Mato Grosso. The total number of rust cases in Brazil is still at the lowest level since Embrapa has been tracking the disease seven years ago, but the number of cases in Mato Grosso is high compared to the last several years.

Generally, the state of Parana leads the way in the number of confirmed cases of rust, but dry weather in the state has helped to limit the spread of the disease in the state, at least thus far. Currently, there are 11 confirmed cases of rust in Parana.

Farmers in Mato Grosso are concerned because the recent heavy rains in the state are helping the spread of the disease. Since the disease is present 20 to 30 days before symptoms appear, researchers are concerned that the number of confirmed cases will increase very rapidly over next few days.

Another factor that will help to spread the disease is the fact that the early soybean harvest has begun in the state. According to the Mato Grosso Institute of Agricultural Economics (Imea), 0.4% of the crop was harvested as of January 5th, and currently about 1% is now harvested. The actual process of harvesting the soybeans helps to disperse the disease spores to nearby fields that have not yet matured.

The soybean plant is most at risk for infection when it is flowering and starting to set pods. Therefore, the soybeans that are the most at risk are the later maturing soybeans that are in close proximity to early maturing soybeans that are being harvested. The spores from the harvested field could easily drift onto the later maturing soybeans that are now setting pods.

The area most at risk in Brazil are the fields in Mato Grosso and Goias where the disease is already present and the hot and humid conditions have been persistent over the last several weeks. If the heavy rains continue in the region, it could make it difficult for the spraying equipment to enter the field and the rains could wash off some of the fungicide, requiring repeated applications. Farmers in the state are being told to stay alert to any announcement of the disease in their area and to be prepared to apply fungicide immediately upon notification of the disease's presence.