All-Rounder Ascra Joins barley Fungicide Arsenal

The approval of ‘all-rounder’ Ascra (prothioconazole + bixafen + fluopyram) for use in winter and spring barley brings another broad-spectrum option for barley disease control programmes.

The addition of fluopyram lifts efficacy over previous standard Siltra (prothioconazole + bixafen) making Ascra the new class-leading barley fungicide. It also has full MAGB approval, important for those targeting a malting premium.

Independent and Bayer Judge For Yourself farm trials have shown mean yield responses of 0.3 t/ha in winter barley varieties and a 0.2 t/ha benefit in spring varieties over Siltra.

Winter barley trials also show consistent yield increases from Ascra over Revystar (mefentrifluconazole + fluxapyroxad). T1 and T2 trials with Ascra at 0.9 l/ha and 0.7 l/ha delivering an uplift of 0.2 t/ha when compared to Revystar at 0.7 l/ha and 0.6 l/ha.

The gap is closer with T2 Ramularia trials, with both having near-identical disease control and yield response scores.

Bayer fungicide campaign manager Rosalind Martin sees Ascra’s broad-spectrum performance as critical with the lack of varietal resilience in winter and spring recommended lists. “We simply don’t have the equivalent of an Extase in the barley variety portfolio.

 “A 7.8 Septoria rating is backed up with strong scores for rusts, mildew and Fusarium. Of close to thirty recommended winter barley varieties, only six get a score of 7 for Rhynchosporium, and of these, all are rated below 6 for net blotch. Newcomer Feeris is rated a 6 for both diseases, but only a 4 for mildew. In spring varieties only four have a Rhyncohsporium rating of 6 or better.”

With every variety having an ‘Achilles heel’ growers have little choice but to factor in broad-spectrum disease control with the weather volatility the UK experiences she believes.

Alongside that broad-spectrum disease potency, the other good news is that Ascra brings all those added benefits we see in wheat. Ascra has a label claim for enhanced greening, root structure and water utilisation, and with rapid rainfastness and excellent leaf adhesion and penetration via the Leafshield formulation, there’s plenty to like suggests Rosalind.

Those non-disease benefits do raise a question with winter barley application timing, especially as Ascra approval is once in a programme. Rosalind’s advice is that growers should use Ascra where disease potency is most needed. “Winter barley is a source crop so light interception at stem-extension and tiller retention is pivotal to yield and with Rhynchosporium, net blotch and mildew activity it’s a natural T1 fit. But those with historical Ramularia problems might be better to save Ascra’s enhanced potency to the T2,” she says.

There’s no doubt over Ascra’s fit at the T2 for spring barley. With full MAGB approval and a cut-off period of GS61 it can be used at GS49, first awns visible, the key Ramularia timing. “It’s important to protect the flag leaf and awns against Ramularia, these are a key driver for yield,” adds Rosalind

Rate is also important with Ramularia control she points out. “We need to be using robust doses of azole to achieve effective Ramularia control. This is why our T2 recommendation is 0.7 l/ha, this delivers close to a 50% prothioconazole dose. To achieve a similar azole loading with other fungicides can make them cost-prohibitive.”

She also argues there’s still no better wheat all-rounder. Looking at the latest round of independent and Bayer trials she has a point.

In various trials, including those conducted by the AICC, pulling apart Ascra, Revystar and Univoq as Septoria protectants last season was almost impossible. “You have to them under intense pressure to separate them,” she notes.

Rosalind puts that down partly to the combination of complementary SDHIs, which are still working well according to Bayer monitoring data. “Ascra is unique in having two SDHIs. Bixafen and fluopyram are separate sub-groups, and where a shift in sensitivity is seen with one it isn’t with the other,” she adds.

She says every fungicide in the armoury has a place in wheat disease control programmes based on variety, drilling date, weather patterns, soils and location.

But Ascra suits so many situations she notes, describing it as the ‘variety versatile’ fungicide. “With rates from 1.0 l/ha to 1.5 l/ha it’s equally suitable for strong or weak rated Septoria varieties with sufficient prothioconazole loading to suit prone yellow rust varieties and provide additional Fusarium suppression for group I wheats.

“Most varieties are weak against eyespot, and in the case of Guium, Astronomer and Merit this is compounded with mildew susceptibility. In addition, prothioconazole in Ascra also contributes to stem-based activity.”

After last season, she says growers need to base wheat fungicide decisions based on what is in front of them. “Nobody could have seen the late foliar pressure coming following the cool, dry conditions during March or April. It is just another reminder not to take anything for granted in farming.”

Her advice is to be informed and adaptable. To help in this regard growers can call on Bayer’s CropCheck initiative. The service offers rapid qPCR testing for Septoria and yellow rust via NIAB with results usually back within forty-eight hours. Growers and agronomists can order a test through the Bayer website here.

CropCheck is just one piece of the puzzle. It must be combined with other agronomic factors such as variety rating, drilling date, soils, weather to date and forecast. “It is a snapshot of disease in specific a leaf layer. Another piece of information to put with everything else,” says Rosalind.

To help understand what the numbers mean, NIAB and Bayer have devised a scoring system. Using a scale of 1 – 100 the service will indicate whether infection in the leaf or leaves tested is in a protectant, early-stage infection or late-stage infection phase and a guide to the level of protection or curative activity needed. “We’re delighted to be partnered with NIAB. Their plant science expertise is helping us understand the data better and what it means for disease control strategies.

“A Septoria score of less than 20 means you’re in a protectant scenario, you are in the optimum position for fungicides targeting this leaf layer and our advice would be to continue with your fungicide programme as planned and dictated by other factors.

“A score between 21 and 49 represents early-stage infection and if conditions are suitable, you can expect to see visible disease in 14-28 days on this leaf layer. Therefore, applying a fungicide in this field is a high priority. Scores above 50 signal that visible disease symptoms are likely to appear in the next 14 days, if not already present. As a result, your fungicide programme may need to be adapted to give maximum curative activity available,” she explains.

For yellow rust, the same 1 – 100 scale applies but the recommendations differ. Rosalind notes this is because yellow rust cycles quicker. The latent phase of Septoria is typically fourteen to twenty-eight days, with yellow rust it can be as short as seven. The early infection stage is much shorter in yellow rust our advice is more focused on two scenarios either protectant or curative.

Also new for this season is eyespot testing. This will not be at the same weekly frequency as Septoria and yellow rust testing but ahead of key timings such as the T1. CropCheck will also be evaluated in barley with tests for Rhynchosporium and net blotch.

Rosalind is delighted the role that CropCheck can play in helping the industry use fungicides more appropriately. “This technology means agronomists and growers are better informed and can adapt fungicide decisions accordingly,” she concludes.