Rust risk increases after damp spell
The much anticipated first signs of yellow rust are now showing up in winter wheat and the recent damp conditions mean it could soon build up in some crops, particularly those that didn’t receive a T0 application.
Paul Fenwick, plant pathologist with Nickerson, confirms that reports of the disease are now fairly widespread in the east, but adds that there’s no immediate cause for alarm.
“We’re talking about infection being found on odd leaves,” he says. “That tells us that it could build up quickly from now on, if we get the right weather.”
So far, it’s only the susceptible varieties, such as Oakley and Robigus, which are showing any signs of the disease. However, a run of perfect nights in April for infection has helped its cause, he explains. “The results of that will become more apparent in the next two weeks.”
And last weekend’s rain will have encouraged lush, soft growth – another of yellow rust’s requirements. “We’ve always said that the potential is there for a problem, and that warning is unchanged. Crops which didn’t get a T0 spray should be checked.”
NIAB’s Rosemary Bayles confirms the presence of yellow rust in the eastern region, and on Oakley. “It’s about a month behind where it would have been if we hadn’t had such a cold winter.
She believes many crops are only just getting going. “Certainly, our trial plots are still relatively backward. I would expect to see much more of it in the next two weeks – we’ve had the warmer weather and the rain. It has the potential to move very fast.”
Given the number of recent sightings, well-timed fungicides will continue to be important, advises David Ellerton of the ProCam Group. “T2 fungicides will need to provide good control of septoria and give rust protection,” he says.
“Yellow rust is out there in wheat, particularly where early sprays weren’t used, and this week’s cooler, damp conditions will suit it.”
He reminds growers to keep the gap between T1 and T2 down to between 3-4 weeks. “The key is to keep the disease in check and prevent it from developing rapidly.
His preference is for a robust three-quarters rate of triazole, plus a minimum third rate of strobilurin at the T2 timing. “Use growth stage rather than the calendar to determine the timing, as the cold spring has delayed crop development.”
TAG agronomist David Parish reports that yellow rust can be found easily in Solstice, Viscount and Oakley, with some growers voicing concern about whether the T1 spray is going to hold it.
“It seems to be taking a while for the triazole to get into the plant and the T1s to kick in. It may be that they caught the yellow rust on its upward cycle, which is why it’s got worse rather than better since spraying.”
Where the disease is causing concern, there are a number of courses of action available, he suggests. “It depends on what’s been done before and how aggressive the rust is. But there’s always the option to apply a spray between T1 and T2, or to pull the T2 forward, if necessary.”
