Chalara ash dieback resistance screening trials

chalara trials site

Identify inherent resistance in common ash (Fraxinus excelsior) trees from a range of provenances across Britain, Ireland and near-continent all sourced from tree nurseries located in the UK . Field trials have been set up at 14 locations in south-east England where Chalara is known to be present. Around 155,000 trees have been planted and will be monitored for signs of infection, tolerance and survival over the five year period of the contract.

Research objectives

  • Source disease free seedlings of common ash (Fraxinus excelsior) representing native seed zones of the British Isles
  • Liase with NGO’s and private landowners to identify suitable planting sites in areas in south-east England where Chalara has been reported
  • Prepare, fence and plant all sites during late spring 2013 in statistically replicated trials.
  • Install temperature logging equipment on selected sites to monitor air temperatures.
  • Observe and monitor disease development and tree survival
  • Select tolerant trees for possible future breeding work and DNA screening by other institutes

Results so far

  • 14 sites identified and 154,464 trees planted by June 2013.
  • First year survival 96% across all 14 sites (81% minimum, 99% maximum)
  • Chalara visually identified on most sites in late summer 2014.
  • Presence of Chalara confirmed on all sites via PCR.


  • Programme started in February 2013; end date April 2018
  • Trees have now completed two growing seasons and symptoms of Chalara have been observed on all 14 sites
  • Presence of Chalara has been confirmed via PCR at all 14 sites


Matt Parratt

Funders and partners

  • Main funder is DEFRA
  • Forestry Commission provides 10% of funding in the first year
  • Part-funded in collaboration with Department of Agriculture, Food and the Marine, Ireland

Key Partners to date are:

Forestry Commission policy

This project is seen as a major contribution to the objectives of the joint Defra-Forestry Commission ‘ Tree Health and Plant Biosecurity Action Plan’ .