Southern Corn Rust Hits Early and Growers Assess What to Do

Southern corn rust has arrived earlier and earlier in Georgia in recent years, but this year is the earliest in recent memory the yield-stealing disease has been confirmed in the state. Corn growers need to decide whether to make a fungicide treatment.

If southern corn rust is not spotted or treated quickly, it can be devastating to corn production in the Southeast, particularly in Georgia where yield losses can be as high as 80 bushels per acre if conditions are favorable for its spread, said Bob Kemerait, University of Georgia Extension plant pathologist.

“If you don’t protect against southern rust early enough and it starts to spread, it’s hard to stop. Once it escapes the bottle, it’s hard to put back in the bottle,” Kemerait said.

Southern corn rust was found June 1 in “very small amount in Seminole County on corn at the R2/blister stage, which is older than most corn in the state,” he says.

The disease was confirmed in the state last year on June 5.

The disease spreads rapidly in storms and with irrigation. And conditions in the region the previous week were favorable for development and spread of the disease, he said.

Kemerait sent an alert about the discovery of the disease to county UGA Extension agents. Growers are encouraged to contact their agents if they have questions or concerns about the disease.

“Now that we have found it, I have enough respect for the disease to say that growers in the southwestern part of the state whose corn has reached or is about to reach tassel apply a fungicide to protect the crop,” he says in an alert. “Growers in other areas removed from extreme southwest Georgia should monitor the spread of the disease. Some may want to make fungicide application either as a safeguard or because they are already making a trip across the field to spray something else.”

If northern corn leaf blight is not a problem in a field, he says, growers have many fungicide options including tebuconazole to manage rust. For longer protective windows or where NCLB is also a problem, growers should apply strobilurin or fungicides that include some combination of strobilurins, triazoles and SDHI active ingredients.

Asian soybean rust continues to spread in southwest Georgia. As of June 1, the disease has been found in small amounts on kudzu in Miller, Baker and Grady counties. “But we can assume that soybean rust is present in low amounts throughout southwest Georgia,” Kemerait said.

Source: Brad Haire, Southeast Farm Press

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