The latest information on ash dieback shows that the disease has spread throughout the island, as 449 confirmed cases have been reported since the first outbreak in 2012.

The disease has now been detected in forest, roadside and hedgerow trees in every county except Laois.

The rapid spread of the disease is similar to trends recorded in other countries. However, as ash is an important forest, hedgerow, roadside tree, parkland and heritage tree in Ireland, the repercussions of the disease are far more serious here.

Separate maps illustrating the location of the disease have been issued by the forest service divisions in both jurisdictions, which we have combined (Figure 1).

Current findings

Since the disease was detected, the number of confirmed findings has increased to 339 (Table 1) in the Republic. There are currently confirmed findings of the disease in 115 forests, distributed over 19 counties.

In 2015, there were 52 individual positive samples from trees in native hedgerows and 76 individual positive samples from trees in roadside and motorway landscaping plantings.

This brings the total to 56 confirmed findings of the disease in native hedgerows in 12 counties and 107 in roadside/motorway landscaping plantings in 13 counties (Table 1).

The most recent statement from the Northern Ireland Forest Service confirmed “a total of 110 premises with recently planted ash and three nursery trade findings have been confirmed infected” up to mid December. The disease is now in all six counties in the North.

Reconstitution

Since December 2012, the Department delisted ash as a tree species approved under the forestry programme and agri-environment schemes – AEOS and GLAS – while the National Roads Authority now choose alternative species for roadside motorway planting.

In March 2013, the Department introduced a reconstitution (Chalara ash dieback) scheme to restore diseased forests planted under the afforestation scheme.

Up to the end of last year, some €2.6m had been paid out under the scheme and over 715ha of infected trees had been cleared and replanted or prepared for replanting with alternative species. The scheme will continue as the disease spreads.

In addition, measures involving the removal and destruction of several thousand ash trees have been undertaken in roadside landscaping plantings, farm landscaping, agri-environment scheme plantings and horticultural nurseries/garden centres.

North-South co-operation

As with plant health generally on the island of Ireland, an all-Ireland approach has been maintained under the North-South Ministerial Council (NMSC) between authorities in Ireland and Northern Ireland with ongoing close co-operation.

The objectives of the All-Ireland Chalara Control Strategy include research into the disease, engagement with industry and other stakeholders, and to “reduce the risk of the disease becoming established in the wider environment”.

Day-to-day implementation of the strategy is co-ordinated by officials from both departments through formal and ad-hoc meetings of the NMSC plant health sub-group.

Ash dieback: settling on an accepted name

Ash dieback, or Chalara dieback of ash, is caused by a fungus Hymenoscyphus fraxineus. This fungus has two phases to its life-cycle: sexual and asexual, according to the Forestry Commission website on the disease (www.forestry.gov.uk/ashdieback).

The asexual stage, which grows in affected trees, attacking the bark and girdling twigs and branches, was the first to be described by science and called Chalara fraxinea, which is the name we have been using up until relatively recently.

The sexual, reproductive stage, which was only discovered later, occurs on infected rachises, or stalks, of the previous year’s fallen leaves.

It was initially called Hymenoscyphus pseudoalbidus, before a taxonomic revision decided on Hymenoscyphus fraxineus, although ash dieback is still the accepted common name. The International Botanical Congress has also agreed that a single fungus should have only one name, even if different stages of the organism have previously been given separate names. Therefore, Hymenoscyphus fraxineus is now widely accepted as the name to use.

SYMPTOMS AND REPORTING

The disease can kill young trees quickly, while mature trees can survive for a number of years. There are a wide range of disease symptoms including:

  • Necrotic lesions and cankers, often diamond shaped, along the bark of branches or main stem.
  • Foliage wilt and discolouration – leaves turn brown or black prematurely at the leaf base and midrib.
  • Dieback of shoots, twigs or main stem, resulting in crown dieback.
  • Epicormic branching or excessive side shoots along the main stem.
  • Brown or orange discolouration of bark – this is particularly noticeable in young ash, as the contrast between the smooth green bark and the discoloured or damaged bark is conspicuous.
  • As the Forest Service points out, these symptoms are not exclusive to ash dieback. Some may be attributable to a number of other causal agents, including frost.

    Forest owners, forest nursery staff, and members of the public are asked to be vigilant for the disease and report (with photographs, if possible) any affected trees to the Forest Service, Department of Agriculture, Food and the Marine, by email forestprotection@agriculture.gov.ie or by phoning 01-607-2651.

    A smartphone app called TreeCheck is available, it uses a GPS-enabled smartphone to locate suspect trees, which can be recorded by the app to allow a follow-up inspection.

    Further details on downloading are available on the Forest Service website (www.agriculture.gov.ie/forestservice/ashdiebackchalara).

    Nursery stock producers should direct queries to local plant health inspector, or queries can be emailed to plantandpests@agriculture.gov.ie or contact the Department at 01-505-8885.

    To avoid spreading the disease, visitors to forests where ash trees may be infected are advised to remove plant debris and soil from clothing and footwear.

    RESEARCH IS THE LONG-TERM HOPE TO CONTROL ASH DIEBACK

    Scientific research on the disease both in Ireland and elsewhere in Europe is regarded as the best long-term way to combat the disease. “The focus is on developing ash tree breeding programmes that will show strong tolerance to the disease,” a Department spokesperson said.

    Breeding for resistance

    Although the Department is involved in a number of Irish and European research initiatives, there is no long-term national research programme for ash breeding for resistance.

    Most research in Ireland is conducted in short-term contract programmes.

    Cooperation with European forest research institutes and agencies is important, but organisations such as the Society of Irish Foresters believe that Ireland’s ability to respond to issues such as ash dieback “is seriously compromised by the lack of an indigenous forest research centre”. The Department is supporting a number of research projects into the control and management of the disease including the following.

    UK forest research

    A five-year project, initiated in 2013, aims to identify individual trees of ash that show resistance or tolerance to ash dieback and to use them for future breeding work and DNA screening by other institutes. The project is being carried out by Forest Research, an agency of the Forestry Commission in the UK.

    This project, part funded by the Department of Agriculture, Food and the Marine, involves 48ha of trial plantings over 14 sites in the east of England and the mass screening of some 155,000 ash trees with 15 different provenances from continental Europe, the UK and Ireland. Over 14,000 Irish ash plants from two distinct seed lots are included in the trials.

    Teagasc project

    Teagasc started a four-year project in 2014 working with researchers in Lithuania and France, with the aim of procuring individual trees of ash that show resistance to the disease.

    If successful, these trees will then be used to bulk up stocks of resistant trees, as well as for establishing seed-producing orchards with resistant parent trees.

    European projects

    The Department is closely following research work carried out in Denmark, which is further advanced than Ireland.

    It is understood over 100 ash trees that are tolerant to ash dieback disease and whose progeny also displays high levels of tolerance have already been selected in Denmark.

    The Department is also monitoring a number of studies in Austria and Germany, who are actively seeking to identify trees exhibiting a similar tolerance and develop a deeper understanding of the interactions between the pathogen and host.

    FRAXBACK

    The Department is a participant in the European Cooperation in Science and Technology (COST) funded action into the disease. FRAXBACK, a four-year COST action started in 2012, aims to generate an understanding of ash dieback, and to produce comprehensive practical guidelines for sustainable management of ash in Europe.

    In addition to 26 European countries, China, New Zealand, Russia and Ukraine are also involved.

    Monitoring the spread

    Last year, the Department included a spore-trapping element aimed at detecting, quantifying, and establishing dispersal patterns around known positive locations.

    The study was conducted with the assistance of experts from the French National Institute for Agricultural Research (INRA) and based mainly in Tipperary and Leitrim, where 192 spore traps were placed during the summer and removed and analysed for the presence of spores.

    Ash dieback spores were found in 14 spore traps.

    The Department has provided research funding through the COFORD to a UCD-led team to model the airborne spread of the disease.

    Together with the University of Cambridge and the Department’s Forest Service, this project aims to assess the risk of ash dieback spread into and across Ireland.