What are Hutton Criteria

A Hutton Criteria occurs when two consecutive days with a minimum temperature of 10°C, and at least six hours of relative humidity (90%). Arising from research funded by AHDB Potatoes and undertaken by the James Hutton Institute, the Hutton Criteria is a significant advancement on the 60-year old Smith period that used wider ranges of temperature and longer periods of humidity. The new criteria has been built in and will improve the reliability and reach of blight risk reporting in time for the 2017 blight pressure season. The new systems will now work with the new criteria in order to help to support decisions, refine action plans and re-empower growers against blight.

A large body of work was undertaken by JHI, funded by AHDB Potatoes, to identify precisely what new criteria might produce the optimum Blight risk prediction results.

Experimental investigations showed that:

  • Reducing the minimum temperature did not improve alert performance markedly
  • The relative humidity threshold should not change
  • Reducing both temperature and relative humidity criteria resulted in an overly sensitive alert system
  • Shortening of the duration of high relative humidity proved most effective

Significant efforts followed up the findings to fully validate the reliability of the new criteria and noted:

  1. Improved performance from 41 to 69 % of > 2000 historic potato late blight outbreaks receiving an alert
  2. Increased proportion of days receiving an alert from 7 to 16% for a 28% gain in performance
  3. Improved consistency in alert performance across all regions of Great Britain

Now: The Hutton Criteria

Two consecutive days:

  1. Each day has a minimum temperature of 10°C
  2. Each day has at least six hours with relative humidity ≥ 90%
  • Performance up from 41 to 69 % of > 2000 historic potato late blight outbreaks receiving an alert
  • Increased proportion of days receiving an alert from 7 to 16% for a 28% gain in performance
  • Improved consistency in alert performance across all regions of Great Britain
  • The future for Blight modelling and alert systems.