tractor spraying wheat field fotokostic/iStock/Thinkstock
DECIDING TO SPRAY: Wheat growers may pass on applying fungicide if they do not see any stripe rust, but they should always spray for head scab, according to Missouri wheat grower Warren Hale.

One fungicide application wheat growers should not miss

Spraying fungicide for head scab is necessary during any growing season.

When growing high-yield wheat, there are two possible applications for fungicides, according to Warren Hale, who farms in Audrain and Callaway counties. One application, he says, farmers may forgo if disease pressure is low. However, there is one application he will always make.

The first application would be to control disease. Hale may apply fungicides to control stripe rust. Stripe rust in wheat can cause yield losses of 40%, with some fields completely destroyed, according to the USDA Agricultural Research Service. It is a major disease of fall-seeded wheat in regions with cool nights, or of spring wheat planted adjacent to infected fall-seeded wheat. Severe losses result when spikes are infected. Hale scouts his wheat, looking for any symptom of the disease. If there is no sign of rust, he will not spray.

Spray for scab
However, Hale will always apply a fungicide at heading. Head scab is a problem for many wheat growers.

According to the University of Missouri, scab is caused by the fungus Fusarium graminearum. This fungus overwinters on host residues such as wheat stubble, cornstalks and grass residues. If environmental conditions are favorable, both warm and moist, the spores germinate and invade flower parts, glumes and other portions of the spike. It not only adversely affects yield, but also the fungi that cause scab produce mycotoxins, which may result in vomitoxin in wheat. And in 2015, the state experienced vomitoxin in wheat that made it impossible for many wheat growers to sell their crops.

For Hale, he considers the fungicide application at heading a given, no matter the weather conditions. Making this application is both labor-intensive and time-critical.

Consider blooming dates
Wheat growers must wait until blooming for this fungicide application. However, depending on the variety, blooming dates vary — so growers must be scouting their fields daily. Why? In order to make the fungicide application effective, the flower head has just 48 hours for the plant to be receptive to the chemical.

Hale has heard of companies touting five to seven days to apply fungicides after blooming; however, he says with high-yield wheat management it is critical to apply within 48 hours. He found that the benefits of the fungicide are not realized the longer growers wait to apply it.

He says wheat growers can manage the rigid spraying regimen by staggering planting dates and wheat varieties.

Fungicide is a necessity in a high-production wheat management system. So make sure it is a part of the crop plan.


TAGS: Crops
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