Tree Diseases, Pests, Triage & Treatment
Trees are living beings, and as such they are susceptible to diseases and disorders just like the rest of us.
- A lot of tree diseases are caused by fungi.
- Other disease-like symptoms are actually caused by environmental stresses and the weather.
- Some tree disorders are the result of bad planting and pests, and a very few are caused by bacterial infections.
This information is provided by Benbow Brothers to help you assess the risk to your trees, and in some cases treat the disease or infection yourself, if you are in any doubt, please contact us for a free assessment of your tree health.
We try to keep this page up to date, but Arboriculture is a surprisingly fast moving science and information is sometimes out of date. This page also contains links to forestry commission information that we are not responsible for.
If you have any questions or concerns about a tree growing on your property please do not hesitate to contact us. We will be happy to examine the tree in question, usually for free and assess any risks to it and your property.
This simply means the tree isn’t getting enough water. It may be due to lack of shade, falling water-table, drought, damage to the roots, salt poisoning, excessive damage to the trunk of the tree or wind exposure. It can often cause the leaves to brown and fall off even though it is not autumn. This symptom is not just caused by dehydration however and so is treated as a disease symptom that we have to use our expertise to discern the cause of the Leaf scorch.
Flooding is very stressful for trees in general. Trees can be slow to show symptoms and it can be difficult to judge the effects on the tree. Typical symptoms include:
- Leaf Scorch
- Small leaf size
- Excessive Watersprouts
- Crown dieback
Flood stressed trees are best treated by applying a low-nitrate fertilizer, and mulching the soil about the roots. Flood water often washes nutrients out of the soil and these require replacement. Since flooding can cause defoliation it can be tricky to decide whether leafless limbs are dead. Dead limbs must be removed for the health of the tree so we recommend contacting us if you are unsure about the condition of your tree.
Truly cold winters are less common than they once were, but frost cracks are a response to bitter cold dry winters especially in Ash and Maple trees. They are long, usually vertical cracks that open in cold winters, but usually close again in warm weather. If this takes place repeatedly the tree may develop a “frost rib” a deep vertical callus ridge. Frost cracks can lead to heart rot and structural failure within the trunk.
Snow and Ice Damage
Fast growing and brittle trees are most at risk during the cold weather. Snow and ice can freeze to the limbs and branches causing them to become overloaded and broken. Snow and ice can also collect in V-shaped crotches where branches join together, especially in fast growing trees and repeated frosts can cause the ice to expand, damaging the tree, and structurally weakening the crown. Eventually, branches overloaded with ice and snow break free and come crashing down. Where possible you should try to safely remove built up snow on a tree. Some smaller fast growing and multiple leader trees should be covered or reinforced with cables during particular harsh winters. You should examine vulnerable trees (especially non-native trees), and prune weakened branches before the leaf-fall. Generally, most British trees cope very well with the winter and do not require summer pruning for winter. Our Tree Surgeons and Arborists have the expertise to assess trees, and plan for long term care whatever the weather may bring.
Shoot (or bud) death
Late spring frosts can kill buds and shoots. This problem is exacerbated by poor tree husbandry such as over irrigation in late autumn or excessive fertilization in late summer as both can cause winter growth.
Not really a disease but often symptoms of a stressed tree, these are straight vertical limbs off side branches (in the case of watersprouts) or roots (suckers). They are usually only weakly attached, and rarely fruitful, but are rapidly growing and can become problematical if left too long. We recommend early pruning of watersprouts and suckers. If you aren’t happy pruning your trees employ a professional, insured, and qualified Arborist to do the work for you.
Most tree disorders and diseases are caused or spread by insect pests. Tree pests are a growing concern in this country. Globalization has proved to be bad news for the ecology of our island with new pests being introduced, bringing new problems for tree surgeons and gardeners in this country.
The most common pests are insects, usually beetles or weevils who thrive on dead wood, but some prefer the extra nutrients available in living wood. Often disease or bark damage will weaken a tree allowing pests access to the wood. Beetles lay eggs beneath the bark, that hatch into tunnelling grubs that eat galleries of passages into the wood. The bored galleries weaken the structure of the tree, and can cause collapse and limb loss.
For a complete list of the current pests that we have to deal with please refer to the Forestry Commission Pest and Diseases page.
If you believe your trees are infested with a pest you should contact us or another qualified Arborist at once. Many pests must be reported to the Forestry Commission by law, and can only be successfully identified with proper training and a sample insect.
Some pests have natural predators which can be used to control the spread of these pests, but sometimes a tree must be treated with pesticides to kill a pest infestation.
As with any infestation, prevention is much better than treatment and wherever possible the risks of infestation should be reduced. If you have any doubts you can call or contact us and request advice and even a free inspection if you think the tree requires attention.
Bacterial infections are caused by single-celled organisms that infest the bark and wood of trees and are as varied in symptoms as they are in humans and animals. The most common symptom in the UK is Leaf Scorch, where the leaves brown and fall as though it were autumn as the tree tries to conserve energy to fight the disease. Bacteria can cause topical leaf scorch, where only infected leaves are browning, or browning occurs with patches upon the leaf’s surface. Since there is no effective treatment for bacterial leaf scorch it is essential that trees with the disease are identified accurately and quickly and where necessary immediately removed.
Leaf scorch is a name given to the symptom of leaves browning and/or falling outside of autumn.
It is a natural response of a stressed tree that tries to conserve reserves of nutrients and energy, exactly like they do through the winter, by dropping leaves. The tree pulls all the chlorophyll from the leaf and it loses its green colour, then drys as no more water is supplied for the photosynthesis process, finally the dry, red, brown or yellow leaf falls.
Since Leaf Scorch is a symptom of a stressed tree it is vital that the correct cause of that stress is quickly identified so that the tree can be treated appropriately. Likely causes include:
- Dehydration – lack of water.
- Flood Stress – over watering
- Nitrogen Burn – caused by too many Nitrogen Salts in the soil from over fertilization
- Soil compaction – packing soil too tightly around roots hampers their ability to draw water and nutrients
- Nutrient Deficient soil – a lack of nutrients that can be fixed by mulching or fertilization
- Transplant shock – moving plants can cause them stress
- Bacterial Infection – Which is, at this time, untreatable
There are many causes of tree stress and each must be separately treated in order to recover the tree. In general, though if you have never fertilized the tree and it is obvious that the ground is not waterlogged, then applying a mulch over the root area, but not up to the trunk, around the tree and gently watering is unlikely to cause harm. The mulch should provide nutrients and control the rate of water uptake. Additionally in some cases light pruning can reduce the amount of water that the tree requires increasing the health of the remaining limbs and trees.
As there are many causes of Leaf Scorch and it can be problematical to identify the cause yourself. Please contact us if you have any doubts as to the cause.