Most ash tree diseases are easy-to-identify, making it easier to control and eradicate the problem. Ashes are regarded as sturdy, landscape trees but varying soil and climatic conditions can induce the spread of some diseases. You should know how to identify common ash tree diseases and treat them.
Ash Anthracnose Disease
Anthracnose disease is common among deciduous trees, particularly maples, oaks, and ashes. Ash Anthracnose is caused by the A. errabunda fungus. Anthracnose infection is usually limited to the foliage but it can spread among the branches, twigs, and buds.
Most Anthracnose-affected ash trees show small cankers, present on the middle and basal-level foliage. During the early spring season, infected ashes might show brown patches developing on the underside of leaves. The leaf tissue develops a characteristic twisted or wrinkled appearance. Premature, unseasonal leaf shedding is common among such trees. The infected leaflets can be found scattered on the surrounding garden bed. Most Anthracnose infections are not severe enough to kill the ash tree. However, they weaken the tree to such an extent that it becomes extremely susceptible to seasonal changes and repeated infestation by garden pests.
It is vital that you maintain a sterile garden bed, particularly during the summers. Remove any form of decaying organic matter. Ensure that the mulch is at least 6-inches away from the bark of the ash tree. Chemical control is usually not needed. Dead and infected branches should be regularly pruned. Regular pruning also helps to create more air circulation within the tree’s foliage, negating the spread of the anthracnose fungus.
Ash Yellow Disease
This is the only plant disease that is destructive enough to cause early death of an ash tree. Ash Yellow is hard to control if its presence is not detected early. It is caused by a fungus that spreads through the garden soil. Not all ash trees are vulnerable to this disease. White Ash and Green Ash are the two most affected species.
Affected trees develop a typical pattern that can be detected through close observation. There is a significant reduction in the volume of foliage along with premature discoloration of the leaves. The faded leaves develop a typical, yellowish appearance along with crusted leaf margins. The stems become thinner and clustered along with developing a powdery appearance on the outside. The foliage might appear a bit swollen at the tips along with a thinner base. Extreme branching is sometimes found among younger branches.
Ash Yellow can be controlled only in its early stages. If the infection spreads to the main bark and the roots, there is little hope for rescuing the tree. If the symptoms are clearly visible, prune-off the affected parts of the tree. Spray anti-fungal spray on the foliage surrounding the pruned site. The health of the garden soil is most critical to preventing the onset of this disease. Ash Yellow is known to attack trees growing in soil beds without proper nutrition. Ensure regular fertilization of the soil bed with basic, NPK fertilizers. This also promotes the development of the useful mycorrhizal fungi. This fungus is the best form of natural immunity against the Ash Yellow pathogen.