Asian rust is close enough to the Equator that a significant weather system (i.e. -- hurricane) could bring spores into North America and the U.S. losses of 80+% of soybean production have been recorded from infected fields. Computer models suggest that 40% losses could be anticipated in U.S. soybean production areas.
No adapted commercial soybean varieties have yet been found that have resistance to rust. Varieties do vary in their response to the disease and some wild varieties show strong tolerance or resistance. Germplasm lines are currently being aggressively screened for resistance in a secure containment greenhouse at the Foreign Disease - Weed Science Research Unit at Ft. Detrick, Maryland. Resistant lines will be developed through conventional cross-breeding methods.
Soybean rust should not be able to withstand winters in the GROWMARK trade area. However, some wild legume species could theoretically serve as overwintering reservoirs. The anticipated mode of infection is expected to be windblown spores from the south. This should be similar to what we currently face with other rust diseases.
Several fungicides provide good control of soybean rust. Manufacturers are already moving to add the disease to labels, where appropriate. Unfortunately, three or more fungicide applications have been necessary to provide adequate control. At current soybean prices, this is prohibitively expensive. There may be some cultural measures that could be taken to minimize the effects of the rust and possibly reduce the number of necessary fungicide applications.
We can't even begin to guess if, or when, Asian soybean rust will strike the U.S. The threat is real and immediate. Bioterrorism is also not out of the realm of possibility. Since we cannot experiment with the pathogen in Midwestern fields, we have limited ability to predict its behavior and impact. If soybean rust hits the GROWMARK trade area in the next few seasons, our ability to respond will be limited to fungicide application. Barring federal cost coverage assistance or the mercy of fungicide manufacturers, soybean rust could be devastating to soybean production in our area.
Note: Leaf symptoms from soybean rust can be confused with other, common soybean diseases (Bacterial Pustule, Bacterial Blight, Brown Spot). We have already had some nervous individuals report suspected incidences of soybean rust. There have been no confirmed cases of soybean rust in U.S. soybeans. All suspected cases have been reviewed and dismissed.