Jan 12, 2010
Brazilian Scientists Advise Farmers To Be Alert For Soybean Rust
Author: Michael Cordonnier/Soybean & Corn Advisor, Inc.
The heavy rainfall this year in Brazil is resulting in very good growing conditions for the soybean crop as well as for soybean rust, a severe fungal disease caused by Phakopsora pachyrhizi. If left untreated, the disease can decimate a soybean crop. The number of confirmed cases of the disease in Brazil is rising at a very rapid rate and it is already the most cases in at least five years. After two growing season of relatively little rust, scientists in Brazil are advising farmers to be extra alert for the disease.
The disease arrived earlier than normal this growing season and farmers are advised to check their fields as frequently as possible with a minimum of two visits per week. They are also advised to monitor their immediate region for news that can alert them to the presence of the disease before it is evident in their fields.
The fungicides used to control the disease are systemic, which means that they need to be reapplied at regular intervals in order to control the disease. Scientists feel that the interval between applications needs to shorter this year due to the frequent rains. Normally, one application every 25-35 days would be sufficient, but this year scientists are recommending a shorter interval between applications. They also advise farmers to make sure they are applying enough water and chemical for good coverage. The traditional fungicides used to control the disease are loosing some of their effectiveness against the disease so scientist are now recommend a combination of fungicides.
Plant breeders in Brazil have developed new soybean varieties are are tolerant to the disease, but there was only a limited amount of seed available to plant in 2009-10. These new tolerant soybeans are called Inox soybeans. Inox soybeans are not resistant to the disease, but they can tolerate a higher incidence of the disease with less yield loss. These tolerant soybeans are not the salvation to the disease, but just another tool used to keep the disease in check. Even with these tolerant varieties, fungicide applications are still recommended, but at a lessor frequency. Soybean varieties with wider resistance to the disease are in development, but they won't be on the market for several more years.