A Texas A&M AgriLife Extension Service plant pathologist recently met with corn growers at a field day near College Station discussing southern rust, a foliar disease that can be problematic for growers and threaten yields.

Dr. Tom Isakeit shared practical advice and application methods at the 2014 Crop Tour, sponsored by AgriLife Extension and BASF Corporation, at the Texas A&M University field laboratory near College Station, which serves as a research and teaching platform for Texas A&M AgriLife.

More than 100 area producers, consultants and industry partners attended the field day. Southern rust, caused by the fungus Puccinia polysora, is the most important foliar disease of corn in the Upper Coast region of Texas, Isakeit said. In some wetter years, when very susceptible hybrids are grown, it may require a fungicide treatment to minimize yield loss.

Dr. Tom Isakeit, Texas A&M AgriLife Extension Service plant pathologist, inspects corn at the Texas A&M University field laboratory near College Station. Isakeit discussed southern rust and use of fungicides as part of the 2014 Crop Tour sponsored by AgriLife Extension and BASF. (Texas A&M AgriLife Extension Service photo by Blair Fannin)

Isakeit told producers application of fungicide early on will help prevent rust from developing on leaves even if the farmer can’t visually see the rust infection.

“Southern rust is recognized by small circular orange pustules and this is in comparison to common rust,  which is reddish and more elongated,” Isakeit said. “If you have corn that is at tasseling to early grain development  stage, you want to check your lower leaves. If leaves have 3 to 5 percent pustules, that will be your trigger to spray.”

In determining whether to spray or not, he said when the crop is still in the vegetative stage, don’t spray. When the crop is near flowering and development of the ear of corn, that would be the most beneficial time to apply fungicide.

Isakeit said there are many fungicides Texas farmers can choose from, but the keyis prevention of rust on upper leaves during the grain fill period.

“Any fungicide would be fine under Texas conditions,” he said. “You can see rust as early as as vegetative stage, but I’ve seen it more as corn is flowering. There is a limited window of time during early flowering and ear development that you would need to worry about disease development and need to spray a fungicide.”

Isakeit suggested farmers read a bulletin he authored on southern rust that is available at http://agrilife.org/plantpathology/files/2011/05/Southern-Rust-of-Corn_2014.pdf

Source: Texas A&M AgriLife