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Farmers are being reminded to test untreated farm-saved seed for disease after Bayer recorded high levels of bunt in trial plots. ‘Ticking time-bomb’ warning for seed disease resurgence

Farmers are being reminded to test untreated farm-saved seed for diease after Bayer recorded high levels of bunt in trial plots.

Cereal seed diseases like bunt (Tilletia tritici) or loose smut (Ustilago tritici or U. nuda) have rarely been seen over the past decade because seed treatments have been very effective at controlling them.

But more growers are using untreated farm saved seed and certified seed – prompting concern that efforts to save costs are having unintended consequences, says Kerry Maguire, Bayer’s agronomic solutions manager for arable diseases.

Untreated gamble

Growers who don’t know their seed dis- ease status are gambling by not using a treatment, says Dr Maquire. “Previously well-controlled seed-borne diseases have the potential to emerge unexpectedly and at high levels, causing significant yield loss.”

Bayer is conducting the disease resurgence trials at Shelford in Cambridgeshire, and at its Stockbridge Technology Centre in Yorkshire.

The trials began with untreated KWS Basset wheat seed and Cassata barley seed – saved two years ago and split into treated and untreated trial plots. Both received maintenance fungicide sprays during the growing season as required.

Treated wheat plots had Redigo Pro (prothioconazole and tebuconazole) applied; while treated barley plots had an application of Raxil Star (prothioconazole, tebuconazole and fluopyram).

Extraordinary results

No trial plots at Stockbridge have shown any visible disease yet – but results from year two in the untreat- ed wheat plots at Shelford have been “quite extraordinary,” says Dr Maguire,

“Bunt infection in the untreated plots ranged from 6.3% to 28% infection, with an average of 15% of ears infected across the trial. In the barley plots there is a small amount of loose smut, but no net blotch or leaf stripe have been seen yet.”

One reason behind the trial was to look at what might happen if seed treat- ments are no longer available – and the difficulties growers may then face when growing certified seed crops – and when saving seed for their own use.

Surprising outcome

Bayer UK regulator manager Dave Holah says: “We were not expecting to see results in year two, so the Shelford wheat trial is a surprise. We hope that we will be able to clean sufficient seed from the untreated plots to be able to drill again.”

One of the challenges of seed-borne disease is that unlike bunt, which occurs on the seed surface, other diseases such as loose smut exist in the seed embryo and cannot be detected without lab testing, nor removed by surface cleaning.