"Hutton Criteria" blight prediction tool

by Scottish Agronomy
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‘Hutton Criteria’ could lead to new prediction tool in fight against blight 

Potato growers in Scotland are being urged to keep on top of potato late blight as improving weather has seen pressure rise to epidemic proportions south of the border. 

 

By the standards of recent seasons, blight in 2016 was relatively slow to get going due in part to the late arrival of spring which kept temperatures and rainfall below the average for the time of year. 

Since 26th May however, weather conditions have led to a gradual reporting of cases from across GB before increasing significantly around 23rd June (see chart). Blight pressure in Scotland is lagging behind that in England by several weeks, but growers are being advised to be vigilant and have a strategy with a plan B.

“Growers need to protect crops against tuber blight if they are to avoid a repeat of the store losses seen in 2014,” says Greg Dawson of Scottish Agronomy.

“Blight in Scotland is largely restricted to the Turriff area west of Aberdeen and to the area around Coupar Angus north of Perth, but the number of cases is anticipated to increase throughout August as conditions continue to support sporulation,” says Greg Dawson.

Tubers are best protected with products offering anti-sporulant activity, but this should not to be confused with those products claiming kick-back activity, he says.

“Where active blight is evident on stems or leaves, it is time to switch to the stronger products, such as Infinito (propamocarb + fluopicolide), Invader (dimethomorph + mancozeb) or Valbon (benthiavalicarb-isopropyl + mancozeb).” 

‘Dansey Period’

Recent data presented at the European Association for Potato Research (EAPR) meeting in Dundee by Siobhán Dancey, a PhD student from the James Hutton Institute reviewing Smith data to inform risk prediction modelling, suggests humidity has a greater to role to play than previously recognised. 

“Siobhán analysed historical data on more than 200 potato late blight outbreaks from 2003-14 and their corresponding Smith Period alerts based on Met Office data. This has allowed the relationship between disease occurrence and predicted risk to be investigated,” says Greg Dawson.

“Reducing the number of hours of high humidity from 11 to six significantly increased the number of late bight outbreaks receiving an alert in the previous seven days and thus seems the more important of the two environmental factors to adjust for accurate late blight prediction,” he explains.

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