image expired

High grain prices coupled with the consequences of the unusual weather mean there is a lot to take into account when finalising important T2 or flag leaf fungicide decisions in winter wheat this season, says Syngenta senior field technical manager, Iain Hamilton. To help growers, he suggests considering five key points:

1. High wheat price

Grain prices of over £170/t make it well worth doing a good job of protecting crop output, says Mr 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.”

2. Rust risks

With yellow rust very much the main disease this season after the dry 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 check the brown rust resistance of your varieties, he says, as it is easy to overlook.

“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.”

3. Septoria tritici risks

After the slow start to Septoria tritici with the dry, cool spring, its development will be influenced heavily by rainfall levels between T1 and T2, says Mr Hamilton, and by variety resistance. Its development tends to be slower on varieties with greater resistance, such as a Graham, he notes.

“If you are in a situation of preventing Septoria tritici, there are various SDHI-based fungicides available, and the differences in products are much smaller than with rusts. If trying to cure infection, you may need to increase the dose of the SDHI treatment or look at a newer fungicide with slightly more curative activity, also applied at an appropriate dose. In both cases, remember the importance of long-lasting activity to protect grain-filling,” he adds.

4. Weather effects

Rainfall increases Septoria, says Mr Hamilton, but do not be lulled into a false sense of security if it is dry. “You also have to consider how the weather after T2 will influence diseases. Two years ago, deluges in June sparked a late-season Septoria epidemic. Alternatively, 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. A T2 application of Solatenol for example, the SDHI in Elatus Era, was found to give an extra 0.23 t/ha over untreated in drought situations even without visible disease.”

5. Spray timing

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 do not let that tempt you into delaying the T2 fungicide, he stresses, even if the interval between the two sprays seems short. Otherwise the flag leaf could be left unprotected for too long.

“For maximum protection, the correct T2 spray timing is still as soon as the flag leaf has fully emerged. 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,” he says.