The crop and soils agent with the University of Wisconsin-Extension office in Fond du Lac County says Fusarium head blight, or scab as it is often called, is showing up in some area winter wheat fields this year. Mike Rankin said the last severe outbreak of this disease was 2004, though this year doesn't appear to be as bad as that one.
"The disease is cause for concern on several fronts," Rankin said. "The causative fungus has the ability to produce mycotoxins, and scab-infected wheat is often severely discounted or rejected when it is sold."
Though some wheat scab can be found every year, when 10 percent of the spikelets are affected within a field there is cause for concern. At this level, yield, test weight, and grain quality are significantly impacted. Rankin notes that a large amount of rainfall or humidity during wheat flowering sets up a bad head scab year.
"It's relatively easy to identify wheat scab. Either entire heads or individual spikelets on wheat heads turn bleach white prematurely," he said. "On closer inspection, there is generally a pink to salmon colored fungus growing at the base of the infected spikelets. Infected grain heads often produce kernels that are small or shriveled. In some situations there may be no kernel produced at all. At harvest time we often see black secondary organisms grow on the wheat head. This makes for a very dirty and dusty wheat harvest."
Fusarium head blight is caused by a fungus that, in addition to wheat, is a pathogen of corn, barley, and other grasses. The fungus overwinters on infested plant residue of cereals, weedy grasses, and corn. The severity of infection varies greatly from year to year depending on weather conditions during flowering.
Fungicides are available for control of Fusarium head blight. Nutritionists suggest that dairy cattle can tolerate up to five parts per million vomitoxin in the total ration dry matter.