As biomass levels in barley crops continue to grow, the T2 timing will be more important than ever for both PGR and disease management to mitigate against big canopies, according to Hutchinsons.
David Howard, head of ICM at the company, said that the significant rainfall across the country means that many typical wet weather diseases will already be present in crops, especially where T0 applications were missed 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 said.
“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 the application of an additional ethephon-based PGR is necessary or if high levels of disease are present.”
Net blotch is chief among the diseases detected, however, Rhynchosporium is also becoming evident, while powdery mildew and brown rust have also been reported.
“Increasing pressure from Ramularia reinforces the value of bringing the timing forward, providing an opportunity for earlier protection against the disease,” Mr Howard said.
“This also allows for an additional spray at GS 49‐59 to top up the T2 spray, improving the persistence of Ramularia control.”
He added that this approach will be particularly valuable as Ramularia may appear in crops soon, due to the stress of rapid growth and temperature fluctuations. An increase in resistant strains of this also means that product choice 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 said.
“The stress reduction and plant health elements of Scyon have also been shown in trials to be useful when included with the T2 fungicide.”
Where Rhynchosporium is the dominant disease, Mr Howard recommends including prothioconazole, which will also help against most other diseases, including mildew.
“The inclusion of an SDHI such as fluxapyroxad or benzovindiflupyr will broaden disease control as well as offer 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.”
Where blotch risk is high, the inclusion of prothioconazole is even more important as recent resistance surveys continue to indicate that strains have reduced susceptibility to 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, especially in susceptible varieties, Mr Howard advises using products containing 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,” said 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.”
For more information go to www.hlhltd.co.uk
