The unusual amount of rain that Kansas has seen in late June and early July means farmers need to be looking for something seldom seen in dryland corn fields in Kansas: fungal disease.
"Now is definitely the time to take a close look at your fields," says Andrew Fisher, fungicide brand manager with Syngenta. "Last year, we had the widest outbreak of northern corn leaf blight that I have seen in my 17-year career. In most of the corn belt, the winter was mild enough for those spores to survive in the residue on the field. And recently, we have gotten the kind of weather conditions that fungus likes."
Fisher said Kansas farmers seldom see fungal diseases in dryland corn because the summers are usually hot and dry, not hot and wet, so people may not be aware that they need to scout fields and apply fungicide if there are signs of disease.
"You should be looking at the ear leaf and up," he said. "Northern corn leaf blight will show up as tiny circular lesions. They are very small at the start of the disease, and producers may be lulled into believing that the infection is minor. Left untreated, they will become large, cigar-shaped lesions that cover the whole leaf."
In reality, by the time you see lesions the disease is already developing in the leaf and it will continue producing spores so that in two or three weeks, it will all over the field. And by then, you have lost 20 bushels of yield potential."
Another disease commonly being seen is gray leaf spot, he said, while there has been some occurrence of both southern leaf rust and common leaf rust. Gray leaf spot will cause yellowing of the leaves, while rust is typically a dark red color, he said.
The good news for producers is that there is a new tool in the box for fighting fungal diseases and it is both costs less and works better than older fungicides. That product is Trivapro. It brings three modes of action to the fight against fungal diseases and is labeled for wheat, corn and soybeans.
"Even better,in 2015 trials, it lasted three weeks longer than older products," Fisher said.
He said spraying will stop the progression of the disease, which left untreated will eventually cover the entire leaf. The lesions already present have already done damage that can't be undone, underscoring the need to act quickly.
"As long as there is moisture to keep it going, the fungus will keep spreading and taking away the leaf surface that the plant needs to produce the biggest, fullest ear possible," he said.
"The optimum time to spray is when corn is at mid-to full tassel," he said. "For much of Kansas, that is right now. The recent heavy rains we've had in much of the Midwest and the current heat make ideal conditions for fungal disease. I would strongly recommend growers scout now.