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Southern Corn Rust1

On Friday Andrew Shirley found Southern Corn Rust in a field in Mitchell County.

Remember Southern Corn Rust is the most important disease on corn! Rain is back in the forecast for next week, which will be favorable for development of rust. Any corn that is approaching (or has passed) the tassel growth stage is worth protecting if the yield potential is there.

Here are some comments from UGA Pathologist Dr. Bob Kemerait:

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.

Here are some comments from UGA Agronomist Dr. Dewey Lee:

“Even though this southern rust infection is earlier than usual, most of our corn crop is a little ahead of schedule.  While this might not be much comfort, it does mean we might have saved at least one spraying.  Last year, it was extremely difficult to stay ahead of southern rust because the infectious time was longer than normal due to favorable conditions for infection.  Some corn in the southern areas of the state is as far along as the R3/R4 stage.  This makes it easier to control rust and reduce the impact since it is much closer to maturity.  Much of the corn crop though, is silking to early ear development (R2/R3) which adds roughly 2 to 3 weeks of time to our potential spraying.

If you have good yield potential (and most irrigated growers do), I would consider spraying a combination of fungicides to provide both a curative and preventative type of action.  There are great choices today from lots of sources.  You may not have a current infection taking place, but spores are active and an application of a combination of fungicides will be great insurance and likely prevent yield loss.  As long as southern rust is active, I would consider staying on a 14 day spray schedule or shorter.  This disease can certainly undermine all your efforts this year and significantly reduce corn yields.”




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