High grain prices and variable spring weather mean finalising T2 or flag leaf fungicide decisions in winter wheat must be carefully assessed this season.
Grain prices of over £170/t make it worth protecting crop output properyl, says Syngenta senior field technical manager Iain Hamilton. At these prices, just an extra 0.25 t/ha from a fungicide is worth a healthy additional £42/ha, he points out.
“Even when we had low disease pressure last year, fungicides still lifted yield by 2 t/ha on average across different wheat varieties over the season. This year, disease pressure is probably higher.”
With yellow rust very much the main disease after a dry early spring, Mr Hamilton says it could remain a key target for T2 – particularly as outbreaks are less predictable with the appearance of new races.
Similarly, brown rust thrives when there is a warm, dry end to the season, so growers and agronomists should check the brown rust resistance of any varieties.
“If rust is your main concern, Elatus Era has been proven in independent trials to be an outstanding SDHI/triazole combination for both these disease, with significant yield benefits and return on investment.”
After a slow start and cold, dry early spring, development of Septoria tritici will be influenced heavily by rainfall levels between T1 and T2 – and by variety resistance. Mr Hamilton says development tends to be slower on varieties with greater resistance, such as Graham.
“If you are in a situation of preventing Septoria tritici, various SDHI-based fungicides are available – and the differences in products are much smaller than with rusts.”
Growers trying to cure infection may need to increase the dose of the SDHI treatment or look at a newer fungicide with more curative activity at an appropriate rate. In both cases, remember that long-lasting activity will help protect grain-filling.
Rainfall increases Septoria, says Mr Hamilton, but do not be lulled into a false sense of security if dry. Growers should also consider how the weather after T2 will influence diseases.
Two years ago, deluges in June sparked a late-season Septoria epidemic. On the other hand, rusts like drier weather. If it does turn into a dry end to the season, certain fungicides have also been shown to have physiological benefits.
In trials, a T2 application of Solatenol – the SDHI in Elatus Era – gave an extra 0.23 t/ha over untreated wheat in drought situations, even without visible disease.
Slow leaf emergence due to the cold spring meant the growth stage for T1 fungicides was often later than normal this season, says Mr Hamilton. But growers should not delay the T2 fungicide – because doing so could leave the flag leaf unprotected for too long.
“For maximum protection, the correct T2 spray timing is still as soon as the flag leaf has fully emerged,” says Mr Hamilton. “If the T1 to T2 interval was short, view this as a bonus for protection. If rain delayed the T1 even further, then timely T2 spraying becomes even more important.”