Agrii survey highlights wheat's growing susceptibility to yellow rust disease

06 September, 2017 - 11:53
Norfolk-grown wheat.  Picture: James Bass

Norfolk-grown wheat. Picture: James Bass

(C) Archant Norfolk 2013

Many wheat varieties commonly grown across East Anglia are becoming more susceptible to a potentially devastating cereal disease, according to a nationwide farming study.

Yellow rust on a wheat plant leaf, pictured at the NIAB open day at Morley Farms. Picture : ANTONY KELLYYellow rust on a wheat plant leaf, pictured at the NIAB open day at Morley Farms. Picture : ANTONY KELLY

The latest national cereal disease survey run by agronomy company Agrii found that changes in the pathogenicity of yellow rust over the past season mean 64pc of mainstream winter wheat varieties now have a lower resistance to the disease than their current Recommended List (RL) ratings suggest.

Monitoring across a series of national variety trials at Agrii Technology Centres and iFarms throughout 2017, the study also found that half the six main candidate varieties are “noticeably more susceptible” to the disease than official figures indicate – providing an early warning ahead of 2017/18 planting.

Agrii research and development manager Jim Carswell said: “A number of varieties are holding their resistance ratings well, with 11 still scoring 8.0 or more in our national survey.

“However, our monitoring also shows many have become noticeably more susceptible to yellow rust over the past season, several seeing their resistance ratings fall by two or more full points.

“Overall, the latest Agrii Advisory List we produced to complement the RL now rates nine of the mainstream wheat varieties at less than 5.0 for yellow rust resistance and five at less than 3.0.

“A progressive fall-off in resistance is only to be expected with varieties that have been widely grown for a number of years. More worryingly, though, we’ve recorded seven of the 11 new varieties on the RL, as well as several Candidates, with yellow rust resistance scores at least a point lower than their official ratings suggest.”

Mr Carswell said later sowing will help reduce yellow rust pressure on wheat varieties, as would well-balanced micro-nutrition to promote the healthiest crops.

“And, despite the withdrawal of the fluquinconazole seed treatment that was such a good early defence, in the majority of cases infections remain eminently controllable with the in-crop chemistry still available,” he added.

“We know how rapidly the disease can take-off, though, and how devastating losses can be when conditions are in its favour or the weather gets in the way of the most timely spraying.

“So it’s especially important to go into the season knowing exactly the level of risk the varieties we’re growing present – especially so with such a large area of wheat almost certain to go into varieties with real yellow rust resistance levels of 6.0 or less this autumn.”

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