Nov 21, 2014

Farmers Warned Soy Rust may Arrive Early in Brazilian Soybeans

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

Scientists in Brazil are alerting farmers to the possibility that soybean rust may enter their commercial soybean fields earlier than normal this growing season. That is the assessment of researchers from the Fundacao Mato Grosso, which is a research agency associated with producers in the state of Mato Grosso.

The Brazilian research service Embrapa tracks the spread of the disease across Brazil and they have already reported 31 confirmed cases of soybean rust in Brazil with the majority of cases being reported in the state of Rio Grande do Sul and the second most in the state of Mato Grosso. During the two previous growing seasons, only three cases had been confirmed by this date. The most cases previously reported was during the 2009/10 growing season when 18 cases was confirmed by mid-November. By the end of the 2009/10 growing season, 2,110 cases of rust were reported in Brazil.

All the confirmed cases thus far have been on volunteer soybeans. These are soybeans that germinate in the field after harvest, along the side of roadways after being spilled out of trucks, or around storage and transportation facilities.

The number of volunteer soybeans in Rio Grande do Sul this year is more than normal because the state received very heavy rainfall during the period between soybean crops (May to September). This allowed the spilled soybeans to continually germinate and grow and it is these plants that harbored the disease and allowed the disease to survive from one growing season to the next. Rust spores can only survive about 55-60 days without a host plant, but unfortunately the continued germination of volunteer soybeans meant that host plants were always available for the disease.

Scientists are also warning that the disease could be worse than normal this year due to the delayed planting of the 2014/15 soybean crop. Soybean planting in the center-west region was delayed this year due to dry weather during the second half of September and the first half of October. The rainfall increased during the second half of October allowing planting to resume. As a result of the delayed planting, the soybeans in the region will be exposed to rust for 2-3 weeks longer than normal before the crop is ready for harvest.