A top price of 2,700gns was achieved and 12 lots sold for 2,000gns or more when the Goostrey herd of Holsteins and Aryshires was dispersed for Griffiths Farming, Cheshire.Yellow rust continues to pose a threat
YELLOW rust continues to pose a threat to winter wheat crops in spite of the prolonged spell of cold weather.
That was the conclusion of three leading agronomists following a yellow rust round table discussion hosted by Syngenta in Cambridgeshire last week.
Reviewing the implications of last season’s yellow rust epidemic for the 2010 crop, Syngenta technical manager, David Ranner, said it came as no surprise that most wheat varieties had some yellow rust infection last year, with Oakley, Solstice and Robigus most severely affected. The resistance ratings of these varieties had fallen sharply as a consequence.
“We do need to consider that some varieties that had yellow rust last year may be more susceptible than their ratings suggest,” said Mr Ranner.
What differentiates the current threat from previous yellow rust epidemic situations is the large number of varieties susceptible to the disease.
Certification figures
Recent past epidemics have tended to occur on one or two highly susceptible varieties, such as Brigadier. But this season more than two-thirds of the winter wheat acreage, based on seed certification figures, will be susceptible to yellow rust (i.e. with a resistance rating of 6 or less. If brown rust is added to the equation, about 85 per cent of the winter acreage will be susceptible to rust infection, with around half the total acreage susceptible to both diseases, said Mr Ranner.
However, while growers should be aware of risks, as long they kept a close eye on susceptible varieties, and were ready to act to combat yellow rust, it could be controlled, said ProCam technical director, Dr David Ellerton.
Winter temperatures were an important driver of rust epidemics, with mild temperatures increasing the disease threat. Clearly conditions have been anything but mild across the whole country over the last month, although both Mr Ranner, Dr Ellerton and TAG agronomist David Parish conceded they were not sure what effect snow cover would have had on yellow rust inoculum.
Well established
Freezing temperatures, and temperatures below -5degsC in particular, stopped yellow rust sporulation but if the disease was well established in wheat crops, yellow rust mycelia could survive in leaves down to very low temperatures, said Mr Ranner.
“If there has been disease establishment in the autumn, the inoculum is there and just waiting to sporulate again,” he said.
Cumulative temperature data for the autumn and winter months to date, suggested for East Anglia and the East Midlands in particular, there had not been sufficient hard frosts to significantly reduce the yellow rust risk. Temperatures during the rest of this month and through February would determine the disease risk and time symptoms started to appear.
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