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How To Tell if a Tree Is Diseased

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  • 24-08-2021
How To Tell if a Tree Is Diseased

How To Tell if a Tree Is Diseased

How can you tell if a tree is diseased? We offer advice about how to tell if our tree is dead, dying or diseased. Find out more about the signs of disease in trees. 

Arborescence Tree Care offer trusted tree surgery services throughout Northampton, Milton Keynes, Bedford. Find out more about identifying diseased trees.

How Can I Tell if a Tree is Dead, Dying or Diseased?

Trees are robust, and we typically leave them to it without any worry; however, it is rare for a tree to be entirely free of disease. 

Healthy trees typically coexist with pathogens and will survive many decades; however, some pathogens or diseases are too much for a tree to coexist with - You can tell if a tree is diseased or dying via the following factors:


Trees shedding leaves under circumstances when they shouldn't.

Leaf blight

The tree's leaves become dead in areas, show discolouration or off-coloured blotches on the leaves.

Decaying roots

Fungus present in the tree's roots or roots begin to break. Signs may also be prevalent on the trunk.

Cankers and cracks

Holes or deep splits within the bark or any peeling bark


Branches are dying or dead.


Crumbly or softwood, usually from present fungus.

Fungus Spores

Fungus spores are present in the tree's bark.

Signs of Disease in Trees

Keeping an eye on your trees for signs of disease is paramount to your tree's health and to prevent the tree from dying. Noticing any harmful factors can help to prevent any further damage or reduce risk and keep your tree healthy post-treatment. 

How Much Does A Tree Survey Cost UK?

Trees change colour throughout the seasons, from green to yellow, to brown; leaves shouldn't be rusty in colour, there are many factors for concern, and we have compiled a list below to help. Signs to look out for include:

How can you tell if a tree is diseased?

Peeling bark

Like enamel, the bark is paramount to protecting a tree's health. Without bark, trees may not have the defences they need nor the ability to retain needed nutrition.

Spots on leaves

If you begin to notice spots or discolouration on your leaves, this is an indicator of fungus or insects within your tree. While in some cases harmless, others being cause for concern or symptoms of a serious disease. 

A trained arborist (tree surgeon) or a certified professional is has the qualifications and expertise to differentiate the two.

Poor growth

Poor growth is a clear indicator of an underlying issue with the tree; its growth could be hampered or lacking needed nutrients. 

Other or specific factors can be assessed by a trained arborist (tree surgeon) or certified professional. 

Holes and cracks in the bark

Commonly associated with decay and typically is of immediate concern. Advice or investigation should be carried out by a trained arborist (tree surgeon) or certified tree service professional.  

An arborist will typically provide free tree advice upon contact on how to proceed forward. Assessment will be provided, and any related issues or harm be followed up and taken care of to prevent dying. 

Dead branches or twigs

Dead branches are a tell-tale sign that a tree is dying or sick. If you snap these branches and there's no green sap, then this is likely the case.

In this instance, it is highly advised to contact a trained arborist (tree surgeon) or certified professional near you regarding any further damage or having a dead tree could be prevented, or current damage rectified, and the tree saved.  

Disease or other factors can lead to a tree becoming unstable, leading to many underlying factors, risks, health concerns, or property damage. 

Common Tree Diseases

Common Tree Diseases

Sadly, there are a plethora of different diseases that can affect trees. Anthracnose is a disease that targets hardwood trees, specifically white oaks, sycamores, black walnuts and dogwoods. Spreading far throughout eastern America, particularly prevalent in highly concentrated areas. 

A common indicator of anthracnose is leaf blight - discolouration or dead patches present on leaves. Many fungi help produce anthracnose employing microscopic particles known as spores that spread through the air; particularly rainy or windy environments help to aid anthracnose spread. These spores need damp weather conditions to germinate, increasing the severity during lengthy wet seasons, such as winter. 

Defoliation may also occur on severely infected or sick trees; this is when a tree begins to lose all its leaves. While a tree may survive or naturally fight off anthracnose, reoccurring defoliation can leave a tree weak and defenceless to another disease. Defoliation is particularly damaging in urban areas as the reduction of sage is the most detrimental factor.

Another disease common with trees is root rot, also known as root decay. While a common sickness, if left unchecked, can actually kill a tree. Roots are vital to the health of a tree; they 'root' the tree to the soil while also providing water and nutrients. Roots continue to grow over a tree's lifespan, meaning the older the tree, the larger the root system. 

Roots can break or lose strength due to these root problems; in turn, this means the likelihood of trees falling over due to wind or other factors drastically increases. Any visual signs of rot, root damage or fungus are determining factors for root decay - it is hard to identify root decay accurately; qualified arborists (tree surgeons) or trained professionals have the expertise to identify and handle root rot. 

Another disease common with trees is root rot

Chestnut blight fungus is a common disease for trees, so prevalent in fact it almost eradicated the American chestnut from eastern American forests. 

Like anthracnose, many fungi help produce chestnut blight fungus, employing microscopic particles known as spores that spread through the air; particularly rainy or windy environments help aid chestnut blight fungus spread. To germinate, these spores need damp weather conditions, increasing the severity during lengthy wet periods. 

The particular fungus is identifiable by an orange/yellow/brown curled horn looking fungus. Currently, there is no cure for chestnut blight fungus.

How Can you Treat a Sick or Dying Tree?

How Can you Treat a Sick or Dying Tree?

Until correctly identified, any afflictions such as pests or diseases cannot be treated. Wrong identifications or wrong treatments may worsen the state of the tree or offer no help. 

Once correctly identified, the appropriate countermeasure can be established - whether this is fungicides to control disease via injecting the substance into the shrub or tree trunk or through fertilisation, pruning, changing habitats and more.  If a disease or pests have considerably affected a tree to the point, it is out of your depth or requires specialist tree care. 

It is highly advised that you contact a qualified arborist (tree surgeon) or trained specialist to rectify the situation before it worsens and prevent dying. A qualified arborist won't wrongly identify the disease and will know the correct actions in how to proceed and can perform them.

We offer tree surveys, tree removal and tree felling throughout Northampton, Milton Keynes and Bedford.

Are you looking for tree surgery in Northampton, Milton Keynes or Bedford? Get in touch with our experienced tree expert today to discus any of the tree services below.