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Southern Corn Rust in Terrell County

Southern Corn Rust has been found in Terrell County.  The disease was found at very low levels but growers need to be aware of this disease because it can explode quickly.

Here is a photo of the disease on a corn leaf:

SCR 2015

Dr. Bob Kemerait, UGA Extension Plant Pathologist, had the following comments regarding Southern Corn Rust in 2015:

Corn growers in south Georgia should be very much aware NOW that rust is here.

Current weather patterns increase the risk.

I believe that any irrigated field corn with good yield expectations and that is at tassel or beyond is a good candidate for treating with a fungicide.

 Corn approaching tassel is also certainly at risk.

 NOTE:  do not mix an aduvant or crop oil with the fungicide if prior to Tassel stage.

Also here are some recent Q&A’s with Dr. Kemerait about the Southern Corn Rust situation for this year

1)     I planted my corn back in March.  Its in the blister stage.  How long do I really need to protect my corn from southern rust?

ANSWER:  Blister stage is certainly at-risk.  Generally I feel you need to protect the crop until the hard dough stage, though some believe you need to protect until the black-layer.

2) There are some really high priced fungicides out there for rust.  How do you feel about tebuconazole compared to these other more expensive chemistries?

ANSWER:  Tebuconazole is a good rust material, but not so good on other diseases like northern corn leaf blight.  Additionally, it does not have the length of protective window that strobilurin and strobilurin/SDHI or strobilurin/triazole fungicides have (2 versus 3 weeks of anticipated protection).  Last season rust was especially bad in Georgia because it showed up so early.  Tebuconazole protected yield, but growers who were hard-hit were better off using better, more expensive fungicides.

3) I spayed my corn crop with a could strobilurin fungicide combination two weeks ago and now you report rust.  Should I go back out and spray at 2 weeks or wait until I reach the full 3 weeks?

ANSWER:  I would advise waiting another week before making a second application.  As you have already sprayed and with a good product and rust pressure is in the initial stages, better to take advantage of the full spray interval and be prepared for a long fight.

If you have any questions about Southern Rust, contact your local county agent for more information.