With the loss of CTL on the horizon, the first azole fungicide to be released in 15 years makes for a timely introduction to the market.
The much anticipated Revystar XE, which is a formulation of the first isopropanol-azole fungicide active to receive approval for use, Revysol (mefentrifluconazole) and the SDHI, Xemium (fluxapyroxad), is said to offer protective and curative activity on all cereals against septoria, rust, mildew, ramularia, rhynchosporium and net blotch, even where resistance has been previously seen.
This is down to the isopropanol-azole’s ‘flexible’ molecule, according to Dr Rosie Bryson, fungicide development expert at BASF, who says the development is a ‘step forward’ in managing resistant mutations.
Unlike other azoles, the mefentrifluconazole molecule can change shape in order to fit the target site, even where mutations are present, giving extra control against highly adapted demethylation inhibitor (DMI) isolates, she says.
“No other azoles have that flexibility – that is what gives the new active its high levels of efficacy.
“We know there are a lot of mutations of some septoria isolates so in the laboratory we took really bad strains for septoria, with as many as nine or 10 mutations in, and all of the azoles that are on the market at the moment were more or less impacted by the mutations.”
Revysol could control all of these existing strains and, although it is a DMI, when cross-resistance patterns were examined, there was no relationship, Dr Bryson adds.
The introduction of Revysol to the fungicide toolbox has reset the clock for disease control says Dr Julie Smith, ADAS senior plant pathology researcher, who saw additional 2.2t/ha yield responses from applications of the new fungicide compared to yield responses from existing azoles in some trials.
During a series of ADAS trials, Revysol gave consistently good results, irrespective of variety resistance ratings, disease pressure, or resistant septoria populations, she adds.
“This shows it doesn’t matter how high [disease] pressure it is and how shifted the population is, you’re still getting control and yield responses were seen in all situations. It’s phenomenal you can see this reaction from an azole product.”
This is down to a combination of attributes giving Revysol its high levels of control, including binding power, fast uptake and rain fastness, according to Steve Dennis, head of business development at BASF.
“Revysol has exceptional long-term protectant abilities, but it’s got a level of curativity that we’ve not seen for a long time from fungicides.
Mr Dennis claims: “Revysol binds on average 100 times more powerfully than conventional azoles, resulting in stronger efficacy.”
Uptake of the fungicide in the plant is rapid, around 24 times quicker than prothioconazole according to BASF.
“This means within an hour we’ve got the same proportion of Revysol in the leaf than you would prothioconazole in 24 hours,” Mr Dennis claims.
“There’s a number of benefits to that – the quicker your azole goes in, the septoria will not have grown so much. It also has other benefits in terms of rain fastnesses and UV radiation.”
He adds: “Azoles are normally affected by uptake in cold conditions, but Revysol is so rapid in uptake, it is virtually temperature independent.”
Kent farmer, Richard Budd, trialled Revystar XE on his farm in 2019, comparing the new treatment to his farm standard on a 14ha field of KWS Lili.
He saw a 0.99t/ha yield benefit when applying Revystar at T1 and T2, compared to the farm standard.
He says: “Up until the end of June/early July we saw no difference. It was end of June into July we started to notice in the Revystar trial areas the crop was a lot greener and we started to lose leaves slower than the rest of the field.
“At harvest, our standard yield was nearly 14t/ha but Revystar adds nearly 1t/ha to our farm standard, purely because it was greener for longer.”
Mr Budd says his strategy for Revystar going forward will be to apply it at T1, to get the crop clean and clear of any septoria that might have come through over winter.
“By using it at T1 it gives me options for T2. If I’ve got a very clean crop there’s potential to use a lighter programme if the year allows me to do so. But I’ve still got the option to go back into Revystar for a second time.”