Corn and soybean fields in Wisconsin look “great,” says WinField United agronomist Tryston Beyrer. In a recent report across all crops, more than 80% show a good or excellent rating. There are a few spots throughout the state that have suffered wind damage, and too much or too little rain, but in general fields are in great shape.
There are some diseases that are affecting Wisconsin corn and soybean fields, likely due to high heat and humidity earlier this season followed by cooler weather later in the season, which caused dew to stick to fields. Beyrer notes that the most prominent diseases he’s seeing in cornfields this year include eyespot, gray leaf spot and northern corn leaf blight. In addition, tar spot has been confirmed in some Wisconsin cornfields this year.
Wisconsin soybean fields have also experienced disease pressure this season. Beyrer says that earlier planting and good growing conditions have closed soybean canopies earlier than last year. Prominent diseases in Wisconsin include brown spot and frogeye leaf spot. Some farmers may also be experiencing pockets of soybean white mold.
As farmers consider a late-season fungicide application, scouting fields — especially soybean fields — will be important. Most soybeans are in the R3 growth stage, and the goal should be to protect the crop as it enters R4, which is the most important time for soybeans when determining yield. Farmers should scout for insects, as Beyrer says that damage from Japanese beetles is the worst he’s seen in a while. He recommends spraying for them at threshold, which for soybeans is about 20% defoliation. Pockets of aphids and thistle caterpillars are also emerging in the state.
Late-season tissue samples will be useful in the coming weeks, especially for farmers who haven’t been taking tissue samples throughout the season. For cornfields, tissue samples won’t necessarily inform what applications to make now, but they will inform management considerations for future seasons. For soybean fields, late-season tissue samples could still potentially inform a late fungicide or insecticide application.
Finally, farmers should check corn pollination progress now. In the days following pollination, farmers can perform a shake test on the ears of corn — any silks that remain attached to kernels were not fertilized. This will be an indication of nutrient deficiencies such as boron, or it may signal stress that occurred during pollination. Watching how different hybrids pollinated gives farmers the opportunity to tweak management strategies in the future.