I have been finding Southern Rust in many area corn fields the last several days. The picture included shows Southern rust in a field that was sprayed with a fungicide 10 days prior. Southern rust is an aggressive disease and we have a long time to maturity/black layer of our corn crops. Several of these fields were just pollinating; this means we have 50 days or more until maturity.
Dr. Bob Kemerait, UGA Extension Plant Pathologist, recently issued the following update:
- SOUTHERN CORN RUST is early this year.
- Southern corn rust is our most important disease of corn.
- Rain is in the forecast, which will be favorable for development of rust.
- I think that corn that is approaching (or has passed) the tassel growth stage is worth protecting if the yield potential is there. I generally would wait to spray for southern rust until your crop is approaching tassel.
- Triazole fungicides (like tebuconazole) are effective against rust (but lack the broader activity against northern corn leaf blight) and have a two week protective window. Strobilurin products and combination strobilurin/triazole of strobilurin/SDHI (Priaxor) have 3 week protective intervals and also a broader spectrum of activity.
- Northern corn leaf blight is generally in check this year.