Much of the field corn in the region is near or at the dent stage and no longer at risk for yield loss from foliar diseases. One disease I frequently receive questions about is southern corn rust. Southern corn rust is a potentially aggressive disease, but the fungus does not overwinter in Virginia and it is typically seen late in the growing season if at all. In 2014, southern corn rust was confirmed in Virginia on August 3, which is relatively early compared to other years. As of this week, southern corn rust has been confirmed from four North Carolina counties (Hyde, Lenior, Beaufort, and Camden) but it has not been observed in Virginia. We very well may see southern corn rust in southeastern Virginia within the next couple of weeks, but there is no need to panic. Yield of corn at or near the dent stage is unlikely to be impacted by the disease, but late planted corn in fields with good yield potential (120 bu/ac +) may need to be protected with a foliar fungicide. Strobilurins are good preventative fungicides whereas triazoles are recommended once sporulation is observed in a field due to their curative activity. A combination fungicide is a good option as long as a strobilurin fungicide has not been applied previously. Wet, warm weather favors disease development. Once sporulation occurs, symptoms of rust are relatively obvious. Lesions start out as raised, blister-like pustules then break open to reveal orange spores. Samples of corn plants with symptoms of southern rust can be submitted to the disease clinic at the Virginia Tech Tidewater AREC (contact Dr. Hillary Mehl, hlmehl@vt.edu).

Southern corn rust