Kansas Wheat: Fungicide application requires due diligence
Today's wheat farmers know that fungicide application can help boost yields when diseases such as rust and scab threaten to affect the wheat crop. This topic is featured as the Kansas Wheat "Video of the Month," on the Internet at www.kansaswheat.org.
During the Kansas Wheat District Meetings, held throughout the state in February, Greg Hudec, technical service representative with Bayer CropScience, pointed out that before application of fungicide occurs, farmers must know whether fungal diseases pose a significant threat to their wheat crop.
Stripe and leaf rust, two of the major threats to wheat in Kansas, typically blow in from Oklahoma and Texas. If those two states suffer from fungal diseases, chances are good that Kansas also could suffer. Also, farmers must understand whether the wheat varieties they planted last fall are resistant to those diseases.
"Fungicide doesn't increase yield, it saves yield," Hudec says. "Historically, our major yield robbers in Kansas are the rust complex. There are some issues with head scab in eastern Kansas, but not as much in western Kansas. The rust complex is probably the wide-spread and consistent of all the diseases. The majority of the fungicides are applied at head emergence or flowering-- if after scab, then flowering. If you sprayed at boot, you'd probably be in good shape with pre-harvest intervals."
Hudec says wheat producers have a choice of fungicide classifications to choose from.
Triazoles cure, eradicate and prevent fungal diseases, while strobilurins prevent diseases only and have good residual properties. Strobilurins must be applied earlier than triazoles in order to prevent the disease from infecting the crop. There are several combination products containing both triazole and strobilurin modes of action on the market, he adds.
Regardless of the chemistry classification, farmers must be aware of the product's pre-harvest interval, as defined on the product label. In 2008, some Kansas farmers began wheat harvest before the pre-harvest interval was met. Therefore, thousands of acres of Kansas wheat were embargoed until the Kansas Department of Agriculture could resolve the issue. Today's fungicide products, Hudec says, have varying pre-harvest intervals.
"The majority of fungicides need to be applied at flag leaf or emergence, up to flowering, if trying to go after scab," Hudec says. "If I could pick one stage, for most foliar diseases except head scab, I'd say boot is a great time to spray. And if you did spray at the boot stage, you would be in good shape at meeting the pre-harvest intervals for today's fungicide products."
Hudec says a fungicide application can be a useful tool to ensure optimum wheat yields. Farmers need to be hands-on managers, he adds, to ensure success. He reiterates the importance of knowing wheat variety weaknesses and observing disease pressures that come from the south through crop scouting. No-till farmers planting wheat into wheat stubble can benefit from fungicide, by reducing the potential of yield-robbing tan spot and powdery mildew.
"Once the disease is on the leaf and affecting tissue, you're not bringing it back. If you want to side on a side of caution, spray too early and not too late," Hudec says.