The risk to corn growers in Georgia from southern corn rust, and perhaps northern corn leaf blight, has increased significantly over the past few weeks. Although the crop continues to progress towards maturity, recent weather patterns coupled with the discovery of southern corn rust in two fields in Seminole County should put corn growers on high alert.
Tropical storm Beryl brought much needed rains to some, but not, all areas of south Georgia. It also brought winds, the winds to carry rust spores over long distances or to move spores of northern corn leaf blight within a field. The southern rust in Seminole County, and very likely elsewhere in southwestern Georgia, is a result of Beryl. Now, with another 10 days of scattered rain, strong winds, high humidity, and prolonged leaf wetness, the conditions are PERFECT for the spread of the fungal diseases. I expect that the potential for spread of rust is widespread over southern Georgia and has certainly occurred beyond Seminole County.
Northern corn leaf blight will not spread long distances but will further develop within fields. Every field of corn in Georgia doesn't need to be sprayed with a fungicide at this time, but conditions are important enough that every grower should weigh the costs and benefits of a fungicide at this time. The most important objective is to prevent development of southern rust in a field and to insure that northern corn leaf blight does not develop and progress above the third true leaf, or so.