Barley diseases may create problems for farmers during late spring, summerWritten by Emilee Gibb
“Most of our barley cultivars are aimed more toward whatever they’re going to be used for, say brewing, so they are focused on more agronomic kinds of issues instead of disease resistance issues,” says University of Wyoming Extension Plant Pathologist William Stump.
There are multiple diseases that could impact barley producers during late spring and early summer months, such as Fusarium head blight, stripe rust and ergot, but producers can take certain measures to limit the field’s susceptibility.
“One of the big issues lately has been Fusarium head blight (FHB), which has been an issue of concern across the country,” says Stump.
FHB is a fungal disease that affects the head and kernels of both wheat and barley. The most notable clinical sign of infection is bleaching of florets prior to maturity. Shriveled kernels, low test weights and a pink to orange mold at the base of florets may also be observed.
In barley used for brewing purposes, FHB can have a major financial impact.
“It also affects malt barley where they get some actual toxins produced, and there’s really strict guidelines on that and brewing barley, so if producers get that, they basically can’t use their barley for brewing,” emphasizes Stump.
While there are fungicides available, many are not very effective. Rather, Stump suggests using management strategies to prevent and control FHB.
“There are certain things we can do, such as avoiding irrigation during the flowering period, because that creates a more conducive environment for infection to take place,” he explains.
Producers using no-till strategies can increase residue management through chopping to speed up infected residue decomposition. Using crop rotations with non-host species such as sugar beets or alfalfa can also help control disease.
“Producers may ask, ‘Is this a situation where should we should plow?’ We’re probably getting more benefits from the minimal till than the detriments of the diseases at this point,” Stump notes.
Stripe rust background
“Another disease that’s a problem right now is stripe rust, and that can be a concern at this time of the year, too,” continues Stump.
Stripe rust is caused by the fungus Puccinia striiformis f. sp. hordei. Another distinct form affects wheat.
The clinical signs of stripe rust in barley are parallel rows of yellow to orange colored pustules on leaves and sometimes the glumes.
The disease favors cool, wet weather. It can persist on susceptible grasses and volunteer wheat.
Stump advises that producers with historical stripe rust problems use resistant barley varieties if available and apply foliar fungicides during the boot stage of development. Producers will need to determine what fungicide to use depending on if they are using the treatment prior to or during an existing infection.
Stripe rust control
As with treating any barley disease, it is important for producers to evaluate the economics of using different control strategies.
“Growers have to weigh the costs and benefit of controlling disease in the fields,” notes Stump.
Any producers interested in knowing if stripe rust is in their area can check the USDA cereal rust website for the current cereal rust situation in the United States.
For the past few years, the University of Wyoming has been assisting with the Cooperative Agricultural Pest Surveys (CAPS).
“They typically will sample some of the barley fields in the Big Horn Basin, and we scrutinize them for the different rusts,” he explains.
Ergot is another disease that can have a significant impact on producers.
“It is also caused by a fungus and infects the actual grains,” says Stump. “The fungus replaces the grain with an overwintering body, a hard sclerotia, and the problem is that those hard bodies that can be harvested when you harvest the barley.”
The sclerotia contain alkaloid toxins, which are toxic for both livestock and humans. The disease infects the grain flowers of barley and a wide range of cool-season grass hosts.
The United States Food and Drug Administration (FDA) has strict regulations on tolerable concentrations of the toxin in barley loads, making it a significant disease for producers to consider.
“The FDA tolerances are at 0.1 percent in a 30-gram sample, so it’s not a lot,” emphasizes Stump.
If toxin concentration is found to be higher than the FDA tolerance, the load will be rejected.
Ergot-infected grains can result in the disease ergotism in humans. Ergotism can result in clinical signs such as hallucinations, gangrene, tremors and death. Strict regulations are in place because heat does not deactivate the toxin.
“It survives the baking process and we still get the toxic effect of the chemicals,” he continues.
Stump explains that ergot is usually environmentally driven, particularly by early, cool, wet weather followed by wet weather during grain flowering. This favors the pathogen and delays the pollination period.
Producers can control ergot infection in fields by utilizing crop rotations because of the short-lived sclerotia. Other management strategies that can be helpful are burial of sclerotia by tillage and mowing wild grasses along field borders before they flower, as grasses are a source of the inoculum.
While ergot was historically a significant problem in the middle ages and is a problem is developing countries, Stump reminds producers that it is an uncommon disease for Wyoming producers to see.
“It’s normally not really a problem. It’s one of those really rare diseases,” he concludes.