Notwithstanding this interpretation of a dangerous ash tree, the presence of dying ash does not in itself confer the power to cut down trees without permission to cut down. When planting replacement trees, site restrictions should be taken into account. It is important to diversify species and think about the origin when choosing trees in order to maximize the resilience of landscapes to pests, diseases and climate change. Consider taking advantage of natural regeneration, especially ash, which shows tolerance for ash death if necessary. The honey fungus (Armillaria spp.) is known to be associated with the death of ashes, but it is important not to neglect other ash-related diseases. For example, the shaggy staple (Inonotus hispidus) and the giant ash clamp (Perenniporia fraxinea). Both diseases have the potential to significantly impair the structural integrity of ash trees. It is believed to be native to East Asia, but dying ashes can be found in most parts of the UK. The disease is particularly destructive to our indigenous and ordinary ashes. In summer, trees are attacked by spores from fruiting bodies in the air, which occur on the central stems of dead leaves – wet conditions favor the production of fruiting bodies. Infection leads to dead branches throughout the crown.
Not all ash trees die directly from a dying ash infection. A tree can be weakened, making it vulnerable to other pests or diseases, and some trees survive infection. The death of the ashes is caused by a fungus called Hymenoscyphus fraxineus (Hi-men-o-si-fus frax-in-e-us). Part of the life cycle of fungi was once known as Chalara fraxinea, hence alternative names such as Chalara or Chalara Ashe Dieback. The current state of knowledge does not provide clarity on the effects of ash mortality on the life expectancy of individual ash trees, although up to 5% of ash trees have genetic tolerance to the disease and many trees that grow in open places may not succumb to the disease and are likely to persist indefinitely. For these reasons, it would be unreliable and premature to downgrade a healthy ash tree or an ash tree that shows tolerance in the categorization of trees according to BS5837 simply because life expectancy would have to be shortened. The possibility of a tree becoming infected by the death of ash trees should not play an important role in determining applications and instructions for pruning or felling protected ash. Simon Ellis, chief executive of Crowders Nurseries in Horncastle, Lincolnshire, said the Horticultural Trades Association wrote to ministers in 2009 warning them of a virulent new strain of ash death disease and calling on them to close the UK`s borders. Symptoms of visible ash death vary, but include leaf wilting, leaf loss and crown death and, in some cases, visible bark damage in branch or trunk tissues that directly contributes to tree decline and death. Growing trees are known to be so weakened that they succumb to secondary pests or pathogens, such as armillaria fungi (honey fungus).
Research has shown that the annual growth generated when a tree is affected by ash dieback is reduced in width and has a reduced container diameter and fiber length (Tulik et al., 2018). Reduced growth will reduce the relative proportion of late wood stronger and denser, and the more severe the infection, the more severe this effect will be. Over several years, this can mechanically weaken the structure of the branches and possibly the trunk, with an increased risk of unusual fractures under stress, during felling or when trees and branches hit the ground. The tolerance of some ash trees, whether genetic or due to site conditions, should not be overlooked when measures are taken to manage the effects of ash dieback. Only trained and experienced tree surgeons or forestry workers should perform work on ash trees that show obvious symptoms of ash die or advanced signs of ash die. This farm note provides guidance to land managers, including owners and practitioners responsible for individual management and small groups of ash trees (by small group we mean areas of trees less than 20 m wide and less than 0.5 hectares) – these trees in fields, hedgerows, edge strips and other open spaces such as cemeteries, gardens and parks that may be infected or infected by the death of ashes. This progress report does not complement or replace published guidelines on tree felling or managing deadly ash trees: it is important to note that poor canopy condition may not be due to ash dieback. Other problems such as drought stress, waterlogging, root damage, soil compaction or other pests and diseases can lead to the decline of ash trees.
Beware of basal lesions, honey mushrooms (Armillaria spp.), shaggy staple (Inonotus hispidus) or giant ash clip (Perenniporia fraxinea), all of which have the potential to compromise the structural integrity of ash. Our new guide, Ash Dying: A Guide for Tree Owners, helps tree owners deal with all the safety risks posed by ash dieback while reducing the environmental impact of this harmful tree disease. The Forestry Commission recommends that you take local tree health training or a tree care course to help you identify symptoms of illness and death and signs of structural problems, and consider issues such as biosecurity. No evidence or research has been uncovered to suggest that wood made before infection by ash death is weakened by the disease. However, when secondary pathogens are present, they should not be overlooked. Forest owners should walk through their property and assess the degree of infection in all their ash trees, planted trees and in hedgerows. In younger trees planted (≤ 30 years), symptoms of the disease include death in the crown, diamond-shaped lesions on the trunk, regrowth of coppice both on the trunk and in the crown, and basal lesions. Not all of these symptoms may be present at the same time.
In older trees, the main symptom of the disease is the death of the crown. Older trees, although infected, tend to be more resistant and need to be closely monitored. Take pictures of the crowns and compare the degree of death over time. Examine the spikes and root supports of these older trees for signs of secondary infections caused by other fungi. Fungi such as armillaria (honey fungus) cause buttocks and root rot, which causes the tree to fall. If necessary, get professional advice. It is important to note that the poor condition of an ash roof may not be due to ash dieback. Other problems such as stress due to drought, waterlogging, root damage or other pests and diseases can cause stress and weight loss in ash trees. However, if it is determined that the death of ash is the cause of the decline, the structural integrity and inherent strength of an ash tree may be severely affected by the disease and associated secondary pests or pathogens; These can lead to a high risk of felling for all operators working on or next to this tree.
The evidence underlying the ash dieback policy and the resulting management recommendations is constantly reviewed; This guide will change regularly. It is also informed by safety guidelines and guidance issued by the forest sector under the UK Forest Industry Safety Agreement (UKFISA). See the note Euroforest – Safety Guidance for Managers on the felling of trees affected by ash dieback. The Forestry Commission gives the following interpretation of the exception for “dangerous trees” in the Forest Act 1967 with respect to ash trees affected by ash dieback.