Loose smut incidence in barley being investigated

The seed-borne disease loose smut has been found in a number of winter barley crops around the country, despite seed having been treated with single purpose seed dressings.

Systemic fungicides in single purpose seed treatments, such as Raxil Star (tebuconazole + prothioconazole + fluopyram) have long been a very effective way of controlling loose smut, which is caused by Ustilago nuda.

In infected plants, masses of spores or “smut” replace the entire barley head, and then infect the open flowers of healthy plants usually through wind or rain dispersal. The spores germinate into the open flower to infect the developing grain, and stays there until the next growing season, without showing any symptoms. The fungus develops within the growing plant, but it is only when the plant reaches maturity the following season it becomes apparent it was infected when the fungus replaces the grain and the cycle starts again.

Usually treating with a systemic fungicide will kill any fungus growing inside.

“It is concerning that a number of incidences of loose smut in treated barley crops have been reported,” says Claire Matthewman, Campaign Manager for Seed Treatments for Bayer. “We are investigating what has caused this, but it is clear that it is wider than just one manufacturer’s products or a particular variety of barley.”

There is some varietal resistance to loose smut in barley, but most commercial varieties are susceptible as it has been controlled effectively by single purpose seed treatments.

“One important consideration for growers is that if loose smut is seen in a crop this season, then it may not be suitable to grow on next season. If growers are considering home-saving seed for next season, it is important to get out now to walk crops and check for infection before the smutted ears disperse.”

Finding out the cause of the infections this season may take some time, Mrs Matthewman adds. “But we will feedback any conclusions as soon as possible.”

If you have any questions, please contact your local CTM or Tweet @Bayer4CropsUK.

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