Yellow rust in wheat is on the march

Watch out for yellow rust now attacking winter wheat crops in both the east and west of the country, growers are being warned.

The disease has been present in some crops since at least the first part of February.

But up until recently it seemed mainly confined to eastern counties and the south Midlands. Now the disease has been identified as far west as Shropshire and Herefordshire, according to latest reports.

"This means the disease has now been confirmed as widely as Lincolnshire and North Nottinghamshire, Cambridgeshire, Kent, Warwickshire, Herefordshire and Shropshire," says Syngenta technical manager, David Ranner.

"The recent breakdown of some of the more popular winter wheat varieties to new strains of the disease is likely to be a key factor behind such widespread appearance. What’s interesting is that the cold winter doesn’t seem to have done much to halt it. Untreated, we know yellow rust can cause yield losses of up to 6 t/ha."

Optimum conditions for yellow rust infection, says Mr Ranner, are between 10-15 degrees C together with prolonged periods of high humidity, such as heavy mists or dews.

"With these sorts of conditions present early in March it’s not surprising the disease has become easier to find. Following these widespread reports we’re advocating that growers should now be building yellow rust into their thinking for disease control right through the season – as these optimum conditions are surely set to reappear as the spring arrives.

"For the first fungicide sprays of the season at T0 and T1, for example, we’re suggesting the use of Cherokee at 0.75 - 1.0 l/ha at T0, or 1.5 - 1.8 l/ha at T1. The cyproconazole active ingredient in Cherokee provides outstanding curativity on rust and up to four weeks protection against future yellow rust infection. Its chlorothalonil component will give added protection against Septoria tritici," he adds.

"In a second wheat situation, Cherokee can be mixed with Amistar at 0.6 - 1.0 l/ha against take-all. This will also add further yellow rust activity. Meanwhile for the T2 timing, growers can now choose from the new fungicide Seguris, or use Amistar Opti + triazole to take care of yellow rust as well as brown rust and Septoria tritici."

Currently, around two thirds of winter wheat varieties are considered to have some level of susceptibility to yellow rust, Mr Ranner points out.