For advice or a free estimate call 0800 030 6212

Tree Diseases Explained

Just like every living thing on this planet, trees are also, unfortunately, susceptible to disease. A tree that lacks either light, water, nutrients or carbon dioxide will struggle to stay healthy and thus be under stress, making it weak and open to contracting diseases. Environmental factors can play a big part in a tree’s health, which means particular seasons can increase the risk of them catching certain types of disease. 

This month, Artemis Tree Services will be covering what to look out for when diagnosing a tree disease.

Anthracnose tree disease as seen on the leaf
(Anthracnose disease)

Common Tree Diseases

Acute Oak Decline. This disease has affected thousands of oak trees in Britain. It became present in trees situated in drought-prone locations, where the pollution levels were high. Symptoms of AOD include black fluid oozing from the tree trunk where there’s missing bark or minor damage. 

Anthracnose. This disease typically targets ash trees, oak trees, maple trees, sycamore trees and other similar types of tree. To identify if your tree has Anthracnose, look for burnt-looking leaves or retreating branches if the tree is extremely weak.

Dothistroma Needle Blight. This fungus usually rears its ugly head in June/July time and changes the colour of the needles of a tree from green to yellow, and later on down the line, red. The affected needles will then begin to shed early.

Phytophthora Lateralis. First identified in 2010, UK, this disease causes tongue-shaped breakages in the bark and bleeding on the outside of the bark, which indicates more lesions underneath. Another sign to look for is red/brown leaves.

Phytophthora Austrocedri. This is a pathogen that discolours and kills off the foliage. Look out for cinnamon-brown coloured wounds on the branches or under the bark of juniper trees.  

Rust. This fungal disease affects the leaves of poplar trees, oak trees, ash trees, birch trees, maple trees and plum trees. To identify the fungal disease, you’ll spot small orange lumps that are full of powdery spores present on the leaves. You’re likely to spot this during the summer months, around August time.

Sirococcus Tsugae. Affects trees including atlas cedar, deodar cedar, cedar of Lebanon, western hemlock, eastern hemlock and mountain hemlock, across the UK. The symptoms include the changing of needle colour from green to brown or pink, fungus on needles and dying seedlings. 

Sweet Chestnut Blight. This fungus enters a tree’s wounds and fissures, and its symptoms include cracks in the bark, stem girdling, wilted brown leaves and orange growths on the bark.

How to tell your tree is in poor health – signs to look out for 

  • Bark abnormalities – visibly deep cracks or holes can be a sign of disease
  • Decay – mushrooms or fungus growing on trees can be a sign of disease
  • Dead branches easily broken and dry branches can be a sign of disease
  • Unusual leaf discolourationleaves changing colour before autumn can be a sign of disease
  • Growing at an anglea lopsided tree can be a sign of disease or damage


If you spot any obvious tree defects, call a local professional who will be able to assist you. Artemis Tree Services serve customers throughout the Hertfordshire areas, providing a reliable and professional service, whatever job we take on. To arrange a free site visit from our tree surgeons, simply contact our friendly team to discuss your project further.


This website uses cookies to enhance your browsing experience...

More information I understand