Nip disease in the bud to build yield

Preserve crop potential from the outset. That’s the view of leading agronomists, who say there is plenty of potential in wheat crops. But there are also risks.

Weather volatility and changing farming practices are impacting disease patterns, partly through an extended green bridge. “The move to minimum or no till strategies is creating the conditions for disease to carry over,” Indigro’s David Boulton points out.

That could be one factor in the levels of eyespot found in the Bayer/NIAB CropCheck initiative last season. Nearly 50% of all samples had the disease, but it was readily found north of the M4 corridor through to Perth. The distribution between the W and R types was fairly even, but DNA/mg figures for W type infection were all higher. Positive results did include Skyfall (7) at Hay Farming, Holbeach St Marks, Lincoln. Skyfall is understood to carry the Pch1 resistance gene. However, it was a second cereal which is a risk factor.

Yellow rust is another disease that could benefit from an extended green bridge. “It is a biotroph, so it survives on living plant tissue,” notes Bayer’s Greg Hanna.

AICC agronomist Patrick Stephenson says don’t use the last two seasons as a steer for 2023 disease control strategies.

The cold conditions of April 21 helped check Septoria pressure and the drought of spring 22 did pretty much the same. But this season the combination of crops being drilled into good beds, in some cases early, and with a relatively mild winter he feels a significant reservoir of disease is possible.

Of course, if the weather helps dry out disease it does alleviate some pressure, but he argues there’s no better approach than to base disease control strategies on risk. That demands a rounded appraisal of variety rating, when it was drilled, crop biomass, and weather patterns and forecast - all essential to protect emerging leaf layers.

His starting position for doing that is, at the start. Nip disease development ‘in the bud’ and keep it that way.

That start could be at the T1, where a Septoria resilient variety has been sown late, but if not then a T0 is a prudent investment. For susceptible yellow rust varieties then prudence becomes a necessity, he considers a contact material like tebuconazole the best option.

T0 options where Septoria is a concern are a multisite such as folpet or possibly a defence elicitor like Lamanarin (Iodus). Nothing is as reliable as CTL, but it is worth consideration, especially as wheat prices are still upwards of £200/t.

When it comes to the two key timings, he feels growers have a good arsenal to choose from. Ascra, Elatus Era (prothioconazole + benzovindiflupyr), Revystar and Univoq (prothioconazole + fenpicoxamid) are all likely to feature again depending on disease spectrum and risk.

In his view, Univoq and Revystar are the strongest Septoria options. Elatus is probably the weakest Septoria option but the best for yellow rust, with Ascra being a good ‘all-rounder’. With its high prothioconazole loading it is particularly useful where the stem-based complex is a consideration.

So, he sees the former two as more natural T2 fits and the latter two as more suited to the T1. But not exclusively, if leaves 3 and 2 are in a protective position ahead of flag leaf sprays then Ascra and Elatus still have a place.

David sees Ascra as a good T1 fit for many situations. He considers it a good all-rounder with the stem-based complex and yellow rust also likely concerns at this timing. He also points out it is good value for money, with crop input inflation a concern for many.

Should we experience another spring drought, all are reluctant to trim T1 rates below manufacturer recommendations, and all see an SDHI as ‘essential’. This is not only due to disease control but also due to physiological factors. “The SDHIs do possess a range of non-disease benefits and for crops in stressed situations these can help,” notes David

Greg agrees and says ADAS trials with Ascra have shown to offer rooting and moisture utilisation benefits. “The ADAS research showed Ascra treated crops having greater root diameter than those treated with azole-based mixtures, including some SDHIs. This aids moisture and nutrient capture, useful in times of stress. T1 decisions need to be based on disease profile and severity, but these physiological properties are nice to have and frequently deliver a yield lift in the absence of disease,” he concludes.