Fusarium head scab, or head blight, is showing up in wheat fields in the Pee Dee. This fungal disease can be distinguished by the bleaching symptom that usually only affects a portion of the grain head. Fusarium can reduce yield as well as test weight. Here are some heads below that are affected.
The photo below shows what it looks like in the field.
Fusarium develops best in warm, humid or wet weather during the flowering stage. The spores overwinter on corn or wheat residue on the soil surface and may also travel with the wind to other fields. Usually, a pinkish orange mass of spores can be observed on the infected head. The affected portions of the head will never mature. Instead the grains will dry out, shrivel up, and can contain a mycotoxin that is unfit for human or animal consumption. Here are some infected grains on the left next so healthy grains on the right.
This photo shows the mass of spores under 30x magnification.
There are some varieties with good resistance to Fusarium including Dyna-gro 9171, Jamestown, Pioneer 26R20, SS 8415, SS8629, TV8525, TV8535, And USG 3555. Chemical control is possible, but we are too far into the season to treat now according to the labels of the fungicides labeled for Fusarium control in wheat. A list of those fungicides can be found here on page 14 under “Head Scab”. Fields that were treated with a preventative fungicide just before heading are showing far lower levels of Fusarium infection than fields that went untreated. The preventative fungicides seem to be doing their job.
To avoid harvesting contaminated grains, combines can be adjusted so that as many small, shriveled grains as possible are blown out the back along with the chaff.
For more info on Fusarium Head Scab, take a look at this APS page.