Tree Diagnosis

July 18, 2017 Blog Comments Off on Tree Diagnosis

Tree Diagnosis By Certified Arborists

Tree Diagnosis

Trees may show signs of illness for various reasons and require a diagnosis. Dead or dying branches can be due to old age, a tree disease, or a pest infection among other reasons. In specific areas, especially dry climates, problems with your tree may also be due to issues such as drought. It is possible to diagnose a tree yourself, although an expert opinion is usually very helpful.

Skills Needed To Diagnose Trees

In order to diagnose the problem with a tree, the tree must be closely examined. This means looking at every aspect of the tree and making detailed notes. Instead of simply noticing the leaves are an odd color, pay attention to see what shade it is and whether there is a specific color pattern. Similarly, simply finding bugs on the tree doesn’t necessarily mean there is an infestation. Even if there is, it doesn’t tell you what kind.
To correctly diagnose the tree, it is also necessary to read or have vast knowledge. This lets a tree expert compare the tree’s symptoms to known illnesses and other problems, letting them easily make an accurate diagnosis. Diagnosing a tree also requires a great deal of practice as various problems may show similar symptoms or one issue could have varying symptoms. It is this, combined with the knowledge required, which makes it essential to consult an expert, such as an arborist.

Steps of Tree Diagnosis

There are several specific steps that need to be taken when conducting a tree diagnosis. First, it is important to know exactly what type of tree is being looked at. Next, you can examine for the symptoms, then read (or use your own knowledge) to compare the symptoms to those present in known infestations or illnesses. After the diagnosis, you can determine whether there is a treatment option and what exactly it would be.

Ask a Tree Expert

As mentioned earlier, it is possible to attempt to diagnose your tree yourself, but unless you are experienced in the subject, it makes more sense to hire an arborist. An incorrect diagnosis could lead to the spread of the illness or infestation or simply the death of the injured tree. While it may seem possible to save money by diagnosing and treating your tree yourself, you don’t want to risk the wrong diagnosis. Arborists and other tree experts will also diagnose the problem more quickly due to their vast knowledge and experience or practice.

Common Tree Diagnosis

Even if you are not the one diagnosing the tree, it is helpful to be aware of some of the most common diagnoses that an arborist may make. While the arborist will likely share the relevant information with you, being familiar with the possibilities ahead of time will make their job easier so they can fix your tree sooner.

Bacterial Diseases of Trees

Fire blight will only affect Rosaceae plants, such as rose, pear, and apples trees. The other type of bacterial disease, canker or bacterial blight, can affect many different species. In cases where the disease has advanced, the twigs will dry out and it will be nearly impossible to find the bacteria, even in a diagnostic lab. Arborists will usually suggest pruning off the dead wood. You can also use fungicides with copper to control bacterial diseases, but watch out for spotting on young shoots.

Foliar Fungal Diseases

There are many types of fungi that can lead to twig dieback, shoot blights, or leaf spots. In most cases, you can simply remove the infected leaves, but you may also need to apply a broad-spectrum fungicide. It is also possible for foliar disease to lead to cankers on the branches or twigs.

Fungal Cankers

If there are cankers on the branches or twigs, your arborist will suggest pruning these areas back until you reach healthy wood. You have to disinfect the pruning tools between each cut to prevent the fungus from spreading, so consider having an expert do it.

Powdery Mildew

This powdery, white fungal growth can occur on top of the buds and leaves, but typically only causes damage in severe cases. There are some types of trees, however, including lilac and rose, which are more susceptible. If this occurs, always rake up fallen leaves and throw them out instead of composting.

Root and Stem Galls

Crown gall bacteria thrive in a range of trees, particularly willow, poplar, pome and stone fruit trees, walnut, and rose. The bacteria will remain in the soil, so replanting must be done with resistant trees. There are also other types of galls, which are specific to particular species or a set of them. Because of this, an arborist’s services are essential.

Root Rot

Root rot most frequently occurs from prior drought stress, flood, over-watering, root damage, or poor soil conditions. Even if certain bacteria are present, it doesn’t mean they were the cause of the issue as Phytophthora and Pythium are usually within any rotted, dead roots. Unless you have a highly sensitive tree, there is not usually a problem with replanting a healthy tree in the same spot.

Leaf Rust on Trees

Rust is a type of fungi that leads to brown, orange, or yellow spots as well as the leaves dropping early. To control this issue, you remove one type of host and rake then throw out the infected leaves. An arborist may also apply sulphur or copper fungicides in some cases.

Vascular Wilts

Vascular wilts typically begin with young branches and twigs dying. These dead twigs will display a brown or black ring. The infection starts in the roots before going upwards via the tree’s vascular system. Some mature trees will quickly die when these wilts occur, while others might separate the infection and have a long life. Arborists will recommend only planting resistant species in the soil as the fungus will still be present for several years.


Most of the time, a viral disease will only lead to noticeable symptoms in cases where the tree is in a stressful environment (such as drought) or is severely pruned. Viruses will not usually spread and sometimes they are easy for an arborist to diagnose, while other times leaf tissue and soil tests are necessary.

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