‘Resistant’ wheat varieties succumb to yellow rust

TRIALS taking place in a Suffolk wheat field have revealed an outbreak of yellow rust across a range of supposedly resistant varieties, according to a membership-based organisation.

Cambridge Arable Technologies (CAT) carries out its trials on a Hanslope clay soil site at Cowlinge, south of Newmarket.

It says it has found a breakdown in yellow rust resistance across of range of supposedly resistant wheat varieties.

At the CAT summer plot tour at the Rosalie Field Station, members could see that many varieties are showing extensive damage from yellow rust. Torch, the Group 3 wheat, was particularly hard hit, with few green leaves remaining in trial plots, CAT said.

“The mild winter, dry Spring and extended periods of rain through the early summer favoured the development of yellow rust, among other diseases, said CAT director Richard Fenwick.

“In untreated plots, several varieties originally classified as resistant to yellow rust have been badly affected and this is reflected in recent HGCA re-classification. Other varieties, such as soft wheat Relay have fared better and are holding up well in our trials. In Group 2, Panorama has retained good resistance as has Scout in Group 3.”

He added: “Farmers have the chemistry to keep rust under control but this comes at a cost, and it is not always possible to spray at the right time.”

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Candidate wheats that are looking promising at this stage include Cougar from RAGT and Croft from KWS, CAT said.

Over several years CAT has been investigating the relative benefits of using coated urea (as KaN) rather than ‘conventional’ urea or ammonium nitrate. This season, trials have been designed to evaluate application rates of each fertiliser at different application timings, ranging from 160 kg/ha to 320 kg/ha with the main dose split 50:50 or 75:25.

Previous trials have illustrated financial benefits of using KaN and the results of the current trial will be released to CAT members after harvest.

The effect of applying different rates and timings of sulphur to breadmaking wheat is also being explored.