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Taking the fight to late blight Potato agronomists and growers are set to be able to use a new potato late blight risk forecasting system which will replace the long-standing Smith Periods method of warnings. Dominic Kilburn writes.

A standing for the

The Hutton Criteria could bring significant improvements to blight forecasting in the UK.

Speaking at the AHDB Agronomists’ Conference at the end of last year, PhD student at the James Hutton Institute in Dundee, Siobhan Dancey, said that the ‘Hutton Criteria’ could bring significant improvements to blight forecasting in the UK, replacing a system still in use today but which hasn’t been updated for 60 years. She said that while the Smith Periods’ threshold is based on two consecutive days with a minimum temperature of 10ºC, and at least 11 hours with relative humidity of 90 per cent or above, research she had performed indicated that, when looking back over historic data (over 2,000 outbreaks between 2003–2014), there had been many cases where blight outbreaks had not received a Smith Periods warning. “Since Smith Periods were first implemented the weather has changed and so have blight populations, and we are seeing a difference in performance across climatic regions. So the question is whether Smith Periods are performing as well as they could,” she said. As part of the AHDB-funded research, Miss Dancey investigated temperature and humidity thresholds, as well as humidity duration, in relation to infection occurring, to see if changes were needed from the current system. It was found that relative humidity only needed to be 90 per cent or above for six hours, for a risk of blight, rather

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than 11 hours as operated by Smith Periods. According to Miss Dancey, when comparing the 2,000 historic potato late blight outbreaks receiving an alert, the Hutton criteria improved the performance of outbreaks receiving an alert. The new system increased the proportion of days receiving an alert from 7 to 16 per cent. In addition, she found improved consistency in alert performance across all regions of the country. Agronomist and specialist potato adviser for Spud Agronomy, John Sarup (left) said: “It’s a concern for potato growers every single year and a tool for identifying high risk periods of disease development is crucial to help us protect our crops and give us the confidence to schedule control activities at the right time, to the right level. “However in recent seasons, blight has been found on crops even before any conventional Smith Periods had been recorded, meaning the current tools and systems just weren’t reliable enough to support precision decisionmaking.” ■

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The Hutton Criteria Two consecutive days: • Each day has a minimum temperature of 10ºC • Each day has at least 6hrs with relative humidity at, or above, 90 per cent

www.lgseeds.co.uk/ovation @lgseedsuk Rothwell, Market Rasen, Lincolnshire, LN7 6DT Tel: 01472 371471 enquiries@limagrain.co.uk

23/01/2017 14:57


Farmers Guide February 2017