By Blake Jackson
The 2026 growing season for field crops has started with relatively low disease pressure, largely due to dry weather conditions following corn and soybean planting.
However, with rain returning to forecasts across parts of Wisconsin, crop specialists are encouraging farmers to closely monitor fields for developing diseases in winter wheat and other crops.
One disease already appearing in several areas is powdery mildew in winter wheat. The disease, caused by the fungus Blumeria graminis f. sp. tritici, produces white, fuzzy growth on leaf surfaces and can eventually spread through the canopy to the flag leaf and heads of susceptible wheat varieties. Small black structures resembling pepper specks may also develop within infected areas.
Despite the recent dry conditions, powdery mildew has been favored by cool nighttime temperatures, high humidity, and frequent dew formation.
Warm daytime weather paired with cool nights creates extended leaf wetness that supports fungal growth, especially when temperatures remain below 80 degrees Fahrenheit. Heavy rainfall can actually suppress the disease by washing spores from leaves.
Experts say fungicide applications for powdery mildew are not always necessary. In many cases, rising temperatures later in the season slow disease development naturally.
Growers are advised to consider the susceptibility of their wheat varieties and monitor weather conditions carefully before deciding to spray.
If cool, humid conditions continue during flag leaf emergence, a fungicide treatment may be beneficial. Triazole-based fungicides are among the most effective options for control.
Fusarium head blight (FHB), also known as scab, continues to be one of the most damaging wheat diseases in Wisconsin. Beyond lowering yields, FHB can lead to elevated levels of deoxynivalenol (DON), commonly called vomitoxin, which can result in grain discounts at elevators.
Researchers recommend combining resistant wheat varieties with fungicide applications for the strongest protection against FHB. Timing is critical, with fungicides providing the best results when applied at the start of anthesis or within five to seven days afterward.
Products including Prosaro, Miravis Ace, Prosaro Pro, and Sphaerex remain among the leading choices for managing FHB.
Farmers are also encouraged to scout for stripe rust as heading and flowering stages approach. Current reports of stripe rust remain limited to states farther south, but continued monitoring is recommended throughout the season.
Photo Credit: gettyimages-milos-cirkovic
Categories: Wisconsin, Crops, Wheat