Asian soybean rust hits Georgia early and corn disease concerns rise

As Georgia’s corn crop enters the tassel stage, farmers are weighing whether to make a fungicide application. And Asian soybean rust is in the state now, the earliest the troubling disease has been detected in Georgia in more than a decade.

The Asian soybean rust was confirmed in Miller County, Ga, located in southwest Georgia May 17, and this means the disease will likely be problematic for Georgia soybean producers this year, said Bob Kemerait, University of Georgia Extension plant pathologist. Growers are advised to stay alert and scout soybean fields. Current conditions favor the spread of the disease within kudzu.

And as Georgia corn progresses, rapidly entering the tassel stage, Kemerait advises growers, at the least the more disease aggressive growers, to consider a protective fungicide application. “This is especially true if southern corn rust has been detected in the area, if northern corn leaf BLIGHT is problematic in a field (typically with a less-resistant hybrid), conditions have been favorable for disease (very wet), the corn was planted LATE or if the grower is aggressive in a disease management program and wants to make sure the crop is protected,” he said.

Kemerait’s further thoughts on corn disease management at this time for Georgia are:

  • As of May 17, we have not found SOUTHERN CORN RUST in Georgia and conditions have not been especially favorable for southern rust.
  • As of May 17, we have had one report of common corn rust from Mitchell County. Common rust typically forms pustules on both sides of the leaf and does NOT need a fungicide application.
  • As of May 17, the only report of northern corn leaf BLIGHT in Georgia is from Ty Torrance in Decatur County. Northern corn leaf blight can be an important problem that requires a fungicide treatment IF it is severe (e.g., a susceptible variety and favorable weather). The NCLB in Decatur County was confined to the bottom leaves and there were only a few lesions on about one plant out of 15. The grower is right to be aware of the problem but I do not think a fungicide is needed for NCLB in that particular field.
  • Northern corn leaf SPOT has been found in Mitchell County by Andy Shirley.  Typically we do not spray for this disease, except in severe cases. The northern corn leaf spot in this field was confined to the lower leaves and did not appear to be spreading.
  • We have not detected southern corn rust in Georgia yet. Conditions over the next few days are more favorable for disease spread, but (overall) conditions have been unfavorable. I would not argue with a grower who wants to apply a fungicide at this time (to corn) as it reaches the tasseling growth stage; HOWEVER I think the grower is better advised to DELAY a fungicide application at this point and wait at least a week or so.

Information in this article courtesy of Andrew Sawyer, UGA Extension agent in Thomas County, at Thomas County Ag.

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