Increasing disease pressure puts more importance on T2 spray for barley
As barley crops build biomass and race through developmental stages, the T2 (GS39-45) timing is more important than ever ...
For both PGR and disease management to mitigate against the risks of big canopies.
David Howard, head of ICM for the firm believes that with the significant amounts of rainfall received across the country throughout the early spring, most of the typical wet weather diseases will already be easily found in crops, particularly where T0’s were not applied due to weather constraints.
“Traditionally the T2 fungicide application in barley has been regarded as less important than the T1 spray, since the ears and smaller upper foliage generally contribute less to yield than in wheat. However, in the case of most hybrid barleys, the larger upper leaves and ears mean that the later sprays in these varieties are increasing in importance compared to those applied at GS 30‐31,” he points out.
“As with wheat, the timing of the T2 application should be less than 4 weeks from the T1 if possible. Historically, many T2 applications have been applied at the ‘paintbrush stage’ as the awns begin to emerge (GS 49). However, it may be necessary to apply slightly earlier from flag leaf up to booting (GS 39‐45), particularly if application of an additional ethephon based PGR is necessary or if high levels of disease are present.”
Chief amongst diseases being detected in barley crops is net blotch following its early entry into crops, he says, however Rhynchosporium is also becoming very evident. Powdery mildew has also been reported and Brown rust is building rapidly in some crops.
“Increasing pressure from Ramularia reinforces the value of bringing the timing forward, providing an opportunity for earlier protection against the disease. This also allows for an additional later spray at GS 49‐59 to top up the T2 spray, improving persistence of Ramularia control.”
Mr Howard believes that this approach will be particularly valuable this year as Ramularia may appear in crops soon, due to the stress brought about by rapid growth and diurnal temperature fluctuations.
He notes that the increase in strains of Ramularia resistant to most fungicide groups other than multi-sites has meant that product choice at this stage is critical.
“Folpet was recently granted moderate control of Ramularia on its label showing how consistently it can benefit against this difficult disease. Trials have also shown that mefentrifluconazole-based products have excellent broad‐spectrum activity including efficacy on Ramularia making them a useful T2 alternative,” he says.
“The stress reduction and plant health elements of Scyon have also been shown in trials to be useful when included with the T2 fungicide.”
However where Rhynchosporium is the dominant disease, Mr Howards recommends T2 sprays should ideally include prothioconazole which will also help towards most other diseases including mildew.
“The inclusion of an SDHI such as fluxapyroxad or benzovindiflupyr will broaden disease control as well as offering physiological benefits. The combination of fluxapyroxad + mefentrifluconazole offers a very rounded option with significant Rhynchosporium control from fluxapyroxad, which is the most potent SDHI on Rhynchosporium with the support of mefentrifluconazole for other late diseases like Ramularia.”
“Recent AHDB trials have also shown that bixafen + fluopyram combinations with prothioconazole offer significant benefits over prothioconazole + bixafen alone.”
He says that where net blotch risk is high, the inclusion of prothioconazole is even more important since recent resistance surveys continue to indicate the existence of strains with reduced susceptibility to the SDHI’s and strobilurins. However, pyraclostrobin is much less affected than other strobilurins and should be included in high‐risk situations.
“As with Rhynchosporium, AHDB trials have also shown that the high loading of prothioconazole in combination with bixafen + fluopyram offers significant improvements in net blotch control compared to prothioconazole + bixafen alone.”
“Benzovindiflupyr+ prothioconazole can be utilised here due to its prothioconazole element but rates will need to be kept high to get suitable amounts of the key active.”
If brown rust is an issue, particularly in susceptible varieties, he advises using products containing the active Benzovindiflupyr as well as tebuconazole, and where increased persistence is required, the inclusion of relevant strobilurins such as azoxystrobin or pyraclostrobin will offer this.
Prothioconazole offers a reasonable level of control of mildew, but where varieties are susceptible and disease is present, the T2 fungicide should include cyflufenamid however he reminds against applying cyflufenamid sequentially.
“Dose rates for T2’s are usually less than for T1’s but this may need to alter if disease pressure remains high or on hybrid barleys where the T2 spray is more important for yield,” says Mr Howard.
“It is important to bear in mind timing and total dose restrictions on the use of fluxapyroxad in crops for malting crops; it must be used before GS45 and the dose rate should not exceed 62.5gai/ha.”
Summary
- Barley crops are at varying degrees of development, but warm weather forecast next week could drive growth and maturity.
- This rapid growth pattern could cause crop stress making them more sensitive to damage from large mixes and more prone to Ramularia attack.
- T2 applications are even more important on hybrid varieties (large flag leaf & Brown rust weakness) and where risk of Ramularia is high particularly where folpet has not already been included in the program.
- Scyon’s ability to reduce crop stress and improve N balance can help mitigate against Ramularia if applied at T2.
- Folpet now has a label claim for the reduction of Ramularia and is active on resistant strains.
- Mefentrifluconazole has also shown good efficacy vs Ramularia.
- There are timing and total dose restrictions on the use of fluxapyroxad in crops for malting.
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