Ash Tree Alert - Native Common Ash Trees Face Surprise Disease Threat

Ash Tree Alert - Native Common Ash Trees Face Surprise Disease Threat

Native Common Ash Trees Face Surprise Disease Threat

Native common ash (Fraxinus excelsior) now faces an unprecedented threat from the latest alien plant pathogen to arrive in the United Kingdom (UK). Chalara ash die-back caused by the fungus Chalara fraxinea sailed into the country in style on a consignment of 2000 ash trees exported by a Dutch nursery to nursery in southern England.

The south of England nursery based in Buckinghamshire subsequently sold the consignment by mail order to 90 customers throughout the UK. Forestry Commission (FC) and Fera (Food and Environment Research Agency), which subsequently intercepted Chalara fraxinea on the trees, identified the 90 customers and gave out instructions for them to dig up, chop up and double-bag the trees before taking them to a landfill for deep burial.

This is somewhat surprising since standard biosecurity practice in such potentially catastrophic pest and disease situations is for the destruction of trees on site by burning followed by a thorough clean up including tools, soil and compost by professionals drafted in specifically to do the job. Transporting tree material infected with a new alien pathogen into the wider environment flies in the face of standard biosecurity practice and common sense.

Be that as it may, FC and Fera have since found the disease in the wider environment on some 500 ash trees planted in a Leicestershire car park and sourced form a nursery in Lincolnshire. Fera is also investigating outbreaks of the disease at nurseries in Surrey and Yorkshire.

Chalara fraxinea was able to ‘walk into’ the UK because although it is rampant across continental Europe, including France, Belgium, Netherlands, Germany and Denmark, it is not an EU regulated pathogen. That means common ash trees can be imported into the UK from any other EU country with absolutely no restriction, inspection or documentation (an EU Plant Passport) that would otherwise declare a clean bill of health.

The disease is particularly prevalent in Denmark where up to 90 per cent of trees in many locations are infected and all are expected to die. Chalara ash dieback has the capacity to inflict on common ash what Dutch elm disease did to English elm in the 1970’s. That is to essentially wipe out the species as forest, woodland, amenity and landscape tree in the UK.

So what’s the damage? Read in full in this September GI