Growers advised to stay vigilant for brown rust – Farmers Weekly
Fungicide sprays at the T2 timing are being strengthened and spray intervals shortened as brown rust continues to cause concern, after the disease infected crops much earlier than expected this...
A mild winter, stressed crops and either delayed or poor T1 applications are believed to have contributed to the current situation. In fact, many susceptible varieties have already received an extra T1.5 fungicide spray to halt the disease.
This is adding to the cost, complexity and frequency of fungicide programmes, in a season where crop potential is likely to have been compromised by the wet weather and most growers are keen to keep a lid on expenditure.
Variety effects
The Group 1 wheat Crusoe is having a particularly bad year, report agronomists, who acknowledge its brown rust rating of 3 and susceptibility to the disease.
However, they point out that it is very unusual to find brown rust in the variety before T1.
“What we’re seeing in Crusoe this year is not normal,” says Dick Neale, technical manager at Hutchinsons.
“Once the disease is established and it’s warm enough, it can cycle in four to five days, which is why there can be a need to keep going back through the crop.”
Other varieties, including Champion and Cranium, are also affected, with the Recommended List ratings being a good indication of their vulnerability, he notes.
“It tends to sit in the bottom of crops, so getting the spray right down into the canopy helps.”
T2 additions
If it is not too late, including either tebuconazole or a strobilurin such as azoxystrobin or pyraclostrobin are options for rapid knockdown at T2, explains Dick.
He stresses that restrictions on the number of applications and label conditions must be adhered to.
“Remember that you are only allowed to use two strobilurins in a season and check the label of your chosen tebuconazole product, as the maximum dose varies and some can only be applied once between GS 30 and 40,” he says.
He accepts this will increase costs. “Where you do need to boost your chosen T2 product, it might add another £5-£10/ha.”
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