Southern rust has been found in Colquitt County today (6/16/22) in a field that is currently in the early R5 (dent) stage of development. Currently corn ranges from VT to R5 stage of development in Colquitt County. If you have questions about how to manage Southern Corn Rust in your area please contact your local county Extension agent.
Here are some thoughts from Dr. Bob Kemerait as far as spraying for southern corn rust:
• Single mode-of-action products are “good” but have a two-week protective window.
• Mixed mode-of-action products have a three-week protective window and better efficacy than do single
mode of action products. Products like these work well, especially when risk is heightened but fields are
sprayed before rust is established in a field.
Will we need to spray twice- now and 3 weeks later?
Possibly. But if you get the fungicide out in a timely manner, a second application may not be needed and, if it is, you may be able to use a less expensive product,
What should our growers spray?
I prefer they use a fungicide that is a mixed mode of action product combining different fungicides. Yes, I have had very good success with Trivapro, Headline Amp, and Veltyma. But I have also seen strong results from other products like Aproach Prima, Stratego YLD, Delano, Fortix, Lucento, etc.
Bob, do you expect the spread of southern rust to continue?
Absolutely I do. Southern rust loves hot. It is dry, but irrigated corn will certainly be a good habitat for
southern rust. UV radiation from clear blue skies could thwart survival of spores in long-range spread, but
certainly spread will continue in Georgia and the southeast.
Bob, you sure like to spend my money. Your fungicide applications are cutting into my profits that are already crippled by diesel prices. How sure are you that spraying my corn at tassel is going to make me money?
Obviously I can’t be 100% sure and ultimately to spray or not to spray is your decision. But I can tell you 3
things. 1) we have now found southern rust earlier than I have ever found it. 2) I believe conditions are quite favorable now for spread. 3) the key to controlling rust is to protect against it before it is present, or at least well-established in a field. Never has a grower who has lots of southern rust in his field late in the season but who didn’t spray tell me he will do that again.
So Bob, you tell us who “should spray”. Is there anyone who can wait to spray?
I would not spray non-irrigated corn if yield potential is low. I would not spray corn in South Georgia that is not at least starting to tassel. I would not spray corn in the Piedmont or northern Georgia. I would hesitate to spray corn where you have a good scout in the field who has not found rust.
