Soybean rust was observed last week in Coffee County, Tennessee (south-central TN) last week. Dr. Heather Kelly with the University of Tennessee posted an on-line article about the find here.
Soybean rust has not yet been observed in Kentucky for the 2016 growing season, but considering the find in Tennessee last week and the weather systems that have occurred the last several weeks, it is highly likely that it will arrive in Kentucky soon. Although the soybean crop is well on its way to reaching maturity in Kentucky, there could potentially be some late-planted or late-maturing fields at risk. At this point, soybean growers can be cautious about soybean rust, but it is likely that no action is needed at this point. For late-planted or late-maturing fields, growers should consider yield potential and disease scouting observations when making a decision on whether a foliar fungicide should be applied (see July 19 KPN article for more information) –
Monitoring the distribution and northwardly progress of soybean rust in the U.S. can be done by going to the Soybean Rust IPM-PIPE website. If soybean plants with suspicious symptoms are observed, it is very important to work with your local county agent to submit a sample to the University of Kentucky Plant Disease Diagnostic Lab for diagnosis. Soybean rust can be difficult to identify, especially when it is at a low incidence and severity. Small, slightly-raised pustules can be observed on the underside of affected soybean leaflets. These pustules often are observed near a leaf vein, where dew or moisture may be retained (Figure 1). The use of a hand lens or a dissecting microscope makes it easier to observe these pustules (Figure 2).
By Carl A. Bradley, Extension Plant Pathologist