Common Tree Diseases

Tree disease is caused by various factors, from weather to tree health, which interfere with the growth and appearance of a tree. It is important to discover the hosts of tree diseases as they are the target of concern when it comes to spreading and treatment. Trees provide homes for wildlife as well as clean air and fuel across the world. They also provide food and water which means that diseased trees could lead to a whole host of other risks, not only for animals but also people.

Trees are under threat from diseases such as Dutch Elm disease which has killed around 60 million! Pests and diseases are infecting native trees and six have reached epidemic levels where the population will die out within a short period of time. However, many diseases can be treated if the bacterial or fungal host is identified. In these cases, necessary measures can be taken in order to bring the tree back to reasonable health. Different varieties of tree and diseases have specific symptoms and signs, life-cycle and management systems.

Tree diseases are categorised into different types which include Conifer Foliar, Hardwood Foliar, Rust and Bacterial.

Common tree diseases include:

Canker Disease

Canker Disease comes in 3 forms, Cytospora, Nectria and Phomopsis which looks like a blister on the bark or branches of a tree. It tends to affect trees such as pine, willow, poplar and spruce and is caused by an infected opening on broken branches which spreads bacteria or fungus. Nectria canker infects honey locust, maple and oak trees whereas Phomopsis canker is found in arborvitae, Douglas fir and Russian olive trees.

Heart Rot Disease

Heart rot disease is often found in deciduous trees including beech, birch, maple, dogwood and cedar. Infection (such as the Fistulina hepatica) is caused by different species of fungus that grow on branches which are damaged from fires, animals or insects. You can suspect Heart Rot Disease if you see conk or mushroom forms growing on the tree.

Powdery Mildew Disease

Trees that are likely to suffer Powdery Mildew Disease include chokeberry, crabapple, catalpa and linden. This is a very common disease which is known to attack many more trees than the common sufferers but mainly those in warm, dryer climates. With this disease, you will notice a white or grey powder-type substance (similar to talcum powder) on the tree leaves.

Root and Butt Rot Disease

Root and Butt Rot Disease come in 3 forms, Armillaria, Hypoxylon deustum and black root rot which can infect the trunks of trees and their roots. The forms attack the moist, poorly protected under surface of the trunk creating rotten plant matter and a black, shiny fungus that spreads up the trunk.

Another common indication of the disease are mushrooms which appear at the base of the tree.

Sooty Mould Disease

Trees such as Boxelder, maple, linden and elms are the most likely to suffer Sooty Mould Disease. Trees with high insect populations are also susceptible to the disease as mould varieties feed off insect honeydew. The main symptom is a black powder-form on the leaves of the tree.

Verticillium Wilt Disease

This is a problematic disease as it attacks the root system of trees and is harder to manage as it spreads very quickly to other plants. Trees that are likely to be infected by this soil-borne disease include maple, elm, catalpa and stone fruit. The tree leaves become lighter in colour and ultimately fall from the branches after a period of time.

There are many ways to prevent tree diseases such as researching their geographical areas to avoid spreading a certain disease. It is effective to buy trees which are resistant to the problematic diseases in the area. It is also encouraged that trees are monitored in terms of fertilizer, weather, soil, available light, temperature and watering conditions in order to prevent and easily identify incidents of disease.