Tree diseases

Tree Diseases

Growing trees in the yard not only adds to the beauty of the landscaping but also increases the property value. But, to make sure that the property reaps the benefits of growing trees, it is vital to ensure that the trees are healthy. Like human beings and all living things, trees have an immune system and any disruption can be fatal. In simple terms, like us, trees are prone to diseases that can drastically reduce their lifespan. Some of the most common tree diseases are listed below, along with possible treatments.

Tree diseases to look out for Some of the tree diseases to look out for include


Anthracnose disease

Anthracnose is a fungus, and a fairly common one too. It generally affects trees that have a bounteous amount of foliage or those which grow in damp environments. It needs water to infect and spread and hence is more prevalent during spring. The fungus camouflages itself in the dark or shade when there is a generous amount of foliage and grows to harm the tree. 

The anthracnose fungus appears on the leaves as yellow or brown spots which later turn into small holes where they appear. It is more of a cosmetic issue than a health risk to the tree. The fungus results in the stunted growth of trees. It also affects vegetable and fruit production, and leaf defoliation of affected plants and trees. It affects deciduous trees such as oak, ash, and sycamore.

 In addition, it can affect shrubs like privet and cause dark and sunken lesions of fruits, flowers, stems, and leaves. Ash, birch, dogwood, hickory, maple, oak, sycamore, and walnut are susceptible.


Anthracnose doesn’t require any treatment. The best way to avoid this fungus is to dispose off the leaves and twigs that fall, and prune the infected leaves, twigs, and branches of the tree to increase air circulation. The best way to prevent this fungus is by improving the air circulation to keep most parts of the tree dry.

Apple Scab disease

Tree Diseases - Apple Scab Disease

Apple scab is a disease caused by a fungus and infects apple and crabapple trees. It also affects mountain ash and pear tree, fruits, and leaves making them inapt for use. It is primarily a leaf disease as opposed to a tree disease. The fungus results in olive green spots on the leaves and the fruits in the initial stages. These spots then turn dark brown and black. The fruits further turn corky and look deformed. It is vital to treat apple scab fungus as it can lead to leaf defoliation.


The best way to treat apple scab disease is to use a fungicide with the active ingredient Fenarimol. Furthermore, there is no need to cut off the infected leaves as the fungicide can easily kill the fungus and stop it from spreading further. But it is vital to cut and dispose off the infected fruit. 

Ash Dieback

As the name says, Ash Dieback is a disease is a fungal infection that typically affects Ash trees. The fungus goes by the name C. Fraxinea or Chalara Fraxinea. It is a new type of infection with the first case recorded in 2012. It is believed that the Ash Dieback came from some other part of the world and it spread through natural means such as the wind into the United States.

When a tree is infected by the fungus, it causes the tree to shed its leaves. The stem shows visible liaisons that look like a burn, similar to crown dieback. If left untreated, the results can be fatal.


Tree diseases - Ash Dieback

The best way to prevent Ash Dieback is to keep an eye for the infection. Keep the surroundings clean and disinfect all equipment regularly. Understand what the symptoms of this disease are, so you can catch it in its early stage. If you spot it, seek help from tree cutting services to remove the infected branches. 

Black knot

Tree Diseases - Black Knot

A potentially deadly infection, the black knot disease disfigures trees and shrubs of the Prunus genus which includes stone fruits such as ornamental cherries and plums. In the initial stages of the infection, the tree develops swellings on the trunk and branches that are greenish brown to brown. In the next stage, the swelling develops into black erupting galls or tumors that infect new branches when they irrupt. Older tumors that die are colonized by fungi which make them white or slightly pink. 


Excessive block knots can be fatal. If the tree trunk or larger limbs are infected, it can lead to tree decline or death. The most effective method to control its spread is pruning.


Blight can affect several species of trees but it is common on pines. Diplodia tip blight, fire blight, red band needle blight, and dothistroma needle blight are some of the variants to be aware of. It stuns the growth and eventually leads to the premature death of young trees. In extreme cases, blight can be fatal to fully grown trees. Changing weather conditions give rise to this infection, which also allows them to spread quickly and easily.


The best way to prevent blight from spreading is to remove and destroy the infected areas, avoid crowding and provide enough airflow, disinfect the pruning tools, and use fungicide on the trees. 

Tree Diseases - Blight

Cedar Rust disease

Cedar Apple Rust or Cedar Rust disease is caused by a fungus. This fungus requires two different hosts to complete its life cycle and typically affects rosaceous plant varieties. The fungus spends the first part of its life on the cedar, typically a year. During spring, the wind carries the infected spores to the second host. The second host is usually located close by, say within a hundred feet to a mile. 

Cedar Rust disease infects the fruits and leaves. It leads to bright yellow-orange spots on them and swollen fruiting bodies on small stunted twigs which fall prematurely. Ash, birch, cottonwood, maples, poplars, plums, and willows are susceptible. 


Similar to Apple scab disease, cedar rust can be treated using fungicide. It can be applied when the leaves start changing color or if they develop rust-like lacerations. You can also spray the fungicide at the start of spring before the fungus infects the tree and symptoms start to show. 

Citrus Gall Wasp

The citrus gall wasp disease is easy to detect. It affects the branches of the citrus tree which appear to be swollen where it is infected by the wasp. The wasp lays eggs within the branches of the citrus tree which causes an infection within, infecting the tree. As more wasps are born, more eggs are laid and the cycle continues. If left unnoticed and untreated, citrus gall wasps can kill your citrus tree.


The most ideal way to treat citrus wasp infection is to cut off the infected branches. Experts recommend removing the branch as soon as you notice a swell or an inflammation. By doing so, you can prevent the infection from spreading to other parts of the tree. You must be vigilant and notice any change in the tree branches so that you can remove the affected branch before it is too late.
Tree Diseases - Citrus Gall Wasp

Cypress Canker

Tree Diseases - Cypress Cancker

Cypress Canker is an infection that spreads with the wind and certain pruning tools. Though it is commonly found in Australia, this disease is found in certain parts of the United States. When infected, the branches turn red and die, sometimes within a day. Furthermore, the branches may turn yellow and have fungus build up in the infected area.


Unfortunately, cypress cankers cannot be prevented. But cutting down the infected branches can prevent them from spreading. 

Emerald Ash Borer

Emerald Ash Borer is a beetle that works like a termite and makes its way through the wood with tunnels, infecting them from within. The most common symptom of this infection or rather an infestation is that the leaves turn yellow followed by dying branches. If left untreated, an emerald ash borer can kill your tree.


The best way to treat this disease is to kill the beetle by using an insecticide that must be injected directly into the infected branch. This is not a guaranteed solution as there might be larvae within, waiting to hatch. The tree may need several treatments. 

Oak Wilt

Tree Diseases - Oak WIlt

One of the most serious tree diseases that quickly result in death is wilts. They are caused by a fungus that clogs the vessels and blocks the water flow to the crown. When it happens, the tree appears scorched and experiences a quick death. The leaves of the infected tree display a partially charred appearance, one of the most visible symptoms of this infection. Some of the best examples include mimosa wilt, Dutch elm disease, and verticillium wilt. 

As the name suggests, oak wilt is a fungal disease that typically affects oak trees and can be fatal to red oak groups. Surprisingly, the white oak family is more resistant to it. The infection starts at the top of the tree, wilting the leaves and turning them brown rapidly. It spreads from tree to tree through sap-sucking beetles or the roots.


You can prevent the spread of this fungus by digging up soil around the infected tree using pruning tools. This blocks the passage of the fungus through the roots. In the case of oat tree plantation, it would be best to remove the tree completely and kill the root and stump to guarantee that the fungus doesn’t spread. 

Photinia Leaf Spot

Similar to various other tree diseases, the photinia leaf spot is a fungal disease as well. It infects several species of trees and causes unsightly red spots on the leaves. These spots begin at the surface and as they progress, they become gray in the center. 


If the infection is isolated, the treatment starts with removing the affected areas and spraying the tree with fungicide. But if the whole tree or plant is affected, then it is best to prune and then spray with fungicide. 

Tree Diseases - Photinia Leaf Spot

Powdery Mildew

Tree Diseases - Powdery Mildew

Powdery mildew is one of the easily recognizable diseases as it leaves behind a talcum powder appearance over the leaves, covering the foliage. It can be caused by various fungal pathogens working together, leaving behind fungal threads or hairs called white mycelia. This disease is common among plants that grow in shady areas, especially when there is no rain and the humidity is high. The fungus targets young plant tissues and results in stunted growth. When infected, the leaves become distorted and turn yellow and the plant experiences a premature death.


This fungal infection can be prevented by planting trees in a space where there is ample light and air. You may spray fungicide and reduce the risk of infection. 

Sudden Oak Death

Sudden Oak Death, a disease that has affected tree plantations in the United States and some regions of Europe is caused by the fungus Phytophthora Ramorum. The fungus infects plantations and forests in bulk, but fortunately, the outbreak is under control. Once infected, the tree can die quite swiftly. 


Unfortunately, there is no treatment for sudden oak death as the trees die immediately. But it is advised to remove the dead tree soon as it dies as it can be unstable quite fast.

Root Rot

Tree diseases - Tree Rot

As the name speaks, root rot is a fungal infection that affects the roots of trees. When infected, it results in pale green or yellow leaves and a wilted appearance even when the weather condition is ideal for the tree to grow. It usually affects trees that grow in poorly drained areas. 


The fungus does not spread naturally and hence it is easy to control. Root rot is caused by the fungus in the soil. The best way to prevent it is to avoid planting trees in downspouts or wet areas. Instead, you may consider water-loving species such as sycamore, willow, cypress, or black gum in such areas. 



In addition to the above, various other tree diseases can adversely affect the trees such as little leaf disease, loblolly pine decline, decay, and annosum root rot, among others. Change in weather or pest infestation is considered to be the main source of infection, which leaves the trees vulnerable to diseases. The best way to avoid tree diseases is to ensure that you plant a tree suitable for the topography, and care for it as required. Regular maintenance can reduce the risk of infection.