Isoflucypram in Iblon is from a new SDHI fungicide sub-class and, according to Bayer, will offer wheat growers a new disease control tool next spring, with performance claimed to be as good as Revystar (mefentrifluconazole + fluxapyroxad) on septoria and Elatus Era (benzovindiflupyr + prothioconazole) against both yellow and brown rust.

Having completed its final season of on-farm testing before full commercial availability, the past year has reinforced the role new chemistry has to play in suppressing the two key diseases, suggests the manufacturer.

The firm this year used the quantitative polymerase chain reaction (qPCR) rapid disease detection technology it is evaluating to track latent septoria infection through the season across 15 farmer-hosted sites in the UK and Ireland.

These grew wheat varieties with a wide range of septoria ratings and each site provided a contribution to Bayers ‘National Snapshot of disease pressure.

As an example of one of those at highest risk, at a site near Long Sutton, close to the Wash in south Lincolnshire, farmer David Hoyles put forward Graham (rated 6.8 for septoria) and LG Skyscraper (5.1) as his varieties for assessment.

James Wilkins, Bayer technical manager, notes that the sites proximity to the Wash and the sea frets this brings about mean yellow rust is a common issue.

Infection However, for much of this season septoria and yellow rust were almost absent, with the former peaking at low levels on emerging leaves of Skyscraper in mid-March.

How quickly that changed, though, was evident from results of late June assessments.

By this point, wet, humid weather sparked septoria into life, while extended leaf emergence and spray timings saw the top four leaves of both varieties carrying disease.

Using rapid qPCR leaf testing we were able to identify tissue showing septoria infection within 48 hours, he says.

Further up the east coast in East Yorkshire, KWS Kerrin, with a rating of 4.8, quickly succumbed to septoria, says Mr Wilkins, with levels on leaf 4 showing a National Snapshot high of 48.387ng per microlitre.

Bayers evaluation of Rapid Disease Detection technology is still at an early stage, but Mr Wilkins believes the 2021 season particularly highlighted its potential.

Back in the dry April and May there was a notable lack of septoria and yellow rust, but the wet weather that followed saw remarkably fast disease build-up, with our National Snapshot results providing the first indication of what was happening inside leaves.

The need to counter climate volatility and shifting disease pressures means the fast results produced by such diagnostic technology and the activity offered by new chemistry means such tools will together have a key role to play in disease control in the coming years, believes Mr Wilkins.

Fungicide decisions are based on actors including varietal susceptibility, drilling date, site fertility and the weather ahead of key growth stages.

Information None of this accounts for what is happening inside leaves, while if symptoms are visible then in most cases it is too late to do much about them.

Rapid Disease Detection technology provides another layer of information to help refine decision-making, providing information on whether the crop is in a protectant or curative situation ahead of key fungicide timings.

Recent seasons have seen disease threat and severity, particularly with yellow rust, shift with the change in weather patterns and this was highlighted by Rapid Disease Detection monitoring and analysis, says Mr Wilkins.

Yellow rust was visible at Long Sutton early in the season, but it never got beyond the base of the plants as leaves emerged, testing revealed the disease wasnt moving up the canopy.

However, we were justified in our decisions with fungicide input as our untreated plots were still heavily infected by the end of May.

We did see the disease at some National Snapshot sites, but at Long Sutton there were 15 frost days in April, continuing into May.

Temperatures also remained cool, with North Sea winds keeping them below 15degC for much of April, while spring sunshine levels were below the five-year average.

A few miles inland though, yellow rust was more of an issue, highlighting how variable disease pressure can be from farm to farm.

The choice of when to use Iblon is likely to come down to varietal susceptibility and disease risk, suggests Bayer.

With a number of new septoria and rust products having been released in recent years, those targeting yellow rust may make the new Bayer active a T1 choice, while farmers for whom septoria is the core focus are more likely to reserve its use for T2, where it offers greening properties in addition to disease control itself.

The missing element in Iblons disease control spectrum is fusarium activity, but Bayer says it plans to co-formulate the active with prothioconazole to offer products that will go some way to addressing this.

Iblon also uses the same Leafshield formulation as Ascra (prothioconazole + bixafen + fluopyram), bringing with it similar benefits for adhesion, penetration, persistence and rainfastness.

The company also plans to offer a number of isoflucypram co-formulations with fluopyram.

In independent trials, this combination is said to have produced a mean yield boost of 0.3 tonnes per hectare over crop treated with Ascra at T2.

However, the firm stresses its commitment to Ascra, particularly where variety rating and drilling date has reduced septoria pressure, and the potency of products such as Iblon or Univoq (fenpicoxamid) are unnecessary.

Core of the chemistry Full details of Iblons key properties are being kept under wraps until the actives full launch later this year ahead of 2022 sales, but early details to have been revealed include the role of the ‘N-cyclopropyl ring that lies at its heart.

This is said to work by expelling a water molecule from the binding ‘pocket where the active meets the target site, thereby enhancing the formers ability to adhere to the latter for maximum efficacy and persistency.

Bayer says its research into exactly how this works is ongoing.

The companys product plans centre around producing all Iblon/isoflucypram co-formulations with prothioconazole as its partner, while some but not all will also include fluopyram.

Bayer says tank mixes with multisite chemistry will be possible, although its own and independent trials suggest variable results from this.

The decision to use Iblon products at T1 or T2 will be left to the discretion of farmers and agronomists.