Fungal infections such as gray leaf spot in corn and frogeye leaf spot in soybeans like the kind of weather Kansas experienced in June.
That makes it good idea to scout fields now and apply fungicide to protect crops from yield-robbing disease, says Eric Tedford, fungicide technical product lead with Syngenta.
While the return of hot, dry weather in the last week or so will help slow down the fungal infection, it likely won't kill it, he said, and problems could quickly spin out of control if wet weather returns in late July and early August.
Even without severe disease pressure, soybeans benefit from the physiological effect of fungicides that help them withstand the stress of hot, dry weather, he said. All plants produce reactive enzymes that are functional to the way the plant matures, but if they are triggered at the wrong time they can cause yellowing and leaf drop.
Plants also produce anti-oxidants that help it stay greener longer and protect it from stress maladies. Applications of fungicide can help growers protect their yields by increases that anti-oxidant production.
In soybeans, Quilt Xcel and Quadris Top are excellent fungicides because they combine two ingredients, one a protectant that destroys the spores of fungi as they land on the leaves and the other a curative that goes to work when a fungus actually penetrates the plant.
The combination of the two provides excellent benefits because the curative works to stop infection that you might not even be able to see yet and the protectant stops later-arriving spores from becoming active. Both of those active ingredients are mobile in the plant. They move upward and outward to protect new leaves as they emerge.
For much of the corn crop in southern and central Kansas, it may be too late to apply fungicide because the crop is at dough or nearing dent stage. The best time for application is V-4 to V-8 from tassel through silking.
Soybeans, however, especially the double-crop beans planted after wheat harvest are likely to benefit from a fungicide application, Tedford said.
He said that some gray leaf spot has been seen on corn in southwest Kansas, along with common rust and septoria. Septoria can be a serious problem in corn/wheat rotations because it lives in the stubble of the corn and infects the next year's wheat crop.