Disease Defense

February 11, 2012 04:37 AM
Disease Defense

Don’t let Fusarium head blight take a toll on yields

Chances are you’ve had a run-in with Fusarium head blight, also known as head scab, more than once. Yields probably suffered, as did test weights at harvest and grain quality for feed.

Fusarium head blight is frequently a problem in eastern states and extending westward to the eastern portions of Kansas, Nebraska and the Dakotas. Warm, wet, humid conditions, such as temperatures between 65°F and 86°F and extended periods of rain or dew, favor reproduction of the fungus.

Typically, farmers experience head scab in wheat two to seven years out of every decade, says Phil Needham, Farm Journal’s High-Yield Wheat columnist.

Wheat is most susceptible during the flowering growth stages, but infection can still occur during kernel development. The first symptoms of Fusarium head blight include a tan, brown or pinkish discoloration at the base of a floret within the spikelets of the head. As the infection progresses, the diseased spikelets turn light tan or bleached in appearance.

The base of the infected spikelets and portions of the rachis often develop a dark brown color. The fungus might produce small orange clusters of spores or black reproductive structures called perithecia on the surface of the glumes.

Field armor. Yield losses of 50% are not uncommon if the crop is not treated with a fungicide.
Farmers can best deter the development of head scab by planting healthy seed and varieties that are most tolerant to the disease. Many of the tolerant varieties contain genes from Sumai 3,
a Chinese wheat variety that plant breeders are using. Needham recommends that farmers plant half to two-thirds of their wheat crop in different varieties that offer good tolerance.

Establishing a uniform wheat stand is also an invaluable deterrence and one Needham says farmers don’t focus on enough.

"A uniform wheat stand can take full advantage of a fungicide, should you need to apply one," Needham says.

In addition to Fusarium head blight, F. graminearum can cause diseases in corn and forages. This means the fungus can survive on many crop residues that remain on the soil surface.

If you determine your wheat crop is at risk of developing the disease, consider using a fungicide.
"To suppress scab, proactively apply a fungicide product, using the right timing, fungicide rate and nozzle technology," Needham says.

Needham recommends using nozzles that spray both forward and backward to help provide good coverage. Providing adequate water volumes is also important for good coverage.

"Don’t skimp on the water. Go with about 15 gal. of water for Fusarium fungicide," Needham says.

Learn more about wheat diseases.

Read Phil Needham's "High-Yield Wheat" column.

Read more wheat news.

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