The 2004 hurricanes brought more then high winds and rain to the United States – they brought Soybean Rust. If conditions are right this fungus may have the potential to damage a large part of the acres in the United States with it’s potential to reduce yields from 10%-80%.
Rust does its damage by causing premature leaf drop. If pod set is far along and the soybean plant is close to reaching maturity, yield loss will be at a minimum. However, if rust strikes early in the season then yield loss will be catastrophic if left untreated. Planting soybeans early is a good cultural practice that can make the plant be more fully developed when the rust strikes to reduce its yield damage. Early planting of soybeans is a good practice in general, as it normally increases yield over later plantings.
Control may be problematic. Preventative treatment of fungicide is the recommended treatment. Once rust is in your field it may be too late for fungicides to control its growth. Growers should be paying attention to extensions and researchers monitoring the area and if rust is found to be moving into the area, preventative fungicides should be applied. Current products that work on soybean rust are Bravo, Echo, Quadris and Headline.
As of now, no resistant varieties of soybeans have been developed to combat rust. Researchers in Brazil have isolated some resistant varieties, but the fungus quickly overcame them within the year. However, rust has been contained in other species and so there is hope. If a resistant line is developed, it normally takes 6-8 years before we see commercially viable varieties on the market. For the short term fungicide is going to be the way to go
What will this mean to us sitting in the heart of the Midwest? The answers may not be all bad. The fungus is spread by spores floating on the wind, which do not over winter in the Midwest. This means that the highest risk areas for rust attacks will be in the Southern and Eastern areas of the United States. With prevailing Western winds, it will be much harder for rust to move into the Midwest, although it can occur. Rust attacks and treatment cost may make soybean production in the south and east uneconomical, which has the potential to put some profitability back into remaining acres.
So far because it has not been condusive for Soybean Rust even in the deep south Rust has not had an impact here like it has in other countries. The Midwest should be pretty insulated from rust and the threat level grows as you move south. Let's hope it remains that way.
By Alex Renk