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  • Dr Stump

Diagnosing Tree Diseases


Our beloved trees are the lungs of the earth so it's important to diagnose and treat diseases before they can become irreversible. Most trees will grow perfectly well in your garden but many could be under stress, so keep a look out as much as you can to see if you spot any damage or changes that might be a sign of pests or diseases. Below are some to look out for.


Leaf damage

Mammals and insects that eat tree leaves are usually harmless for a tree, however it is a good idea to be mindful because some insects can cause problems for tree health. One of the most common insects who will happily enjoy a tree for dinner is the Horse Chestnut Leaf Miner, this tiny insect may be difficult to see but is hard to miss the destruction they leave behind. This is the larvae of the moth Cameraria ohridella which are only about 4-5mm in length. During the early summertime, they can lay up to 180 eggs on the leaves. You may notice brown spots appearing on the leaves which can be removed along with any fallen leaves in the autumn so they can't overwinter.


Wilting leaves

Wilting leaves can be a sign of stress. Leaf health is determined by three elements; garden soil, sunlight and temperature. If you notice wilting leaves, try to identify what these might mean for your tree. It could be that your tree is sitting in the wrong soil type or prefers to be positioned in a shady area of the garden for example. If you are sure the tree is placed where it’s happiest, then there may be other factors at play. It's important to research the species of tree you have to pre-empt the most common disease specific to that tree. For example, a common disease that is killing 80% of Ash trees is Ash Dieback which currently has no cure. If you’re struggling to determine what could be causing your tree’s leaves to wilt, contact a tree surgeon who will be happy to help.


Bleeding cankers

Another way that trees can express stress is through ‘bleeding’ in their trunks. This ‘bleeding’ appears as a dark red fluid that oozes from cracks in the bark, the foliage around the infected area will be sparse as the branches start to die back. There can be many causes for this such as excessive freezing, pollution, drought or disease. One of the most common deadly pathogens is Phytophthora which blocks the transport of water through the tree. The most effective way to solve this is to ensure you are providing the tree with good drainage and practising good water management.


How can you help your tree have the best chance?

It is extremely important to make sure that you have the right location for the specific type of tree that you have. For example, Oak, Yew and Juniper prefer drier soil while Alder and Willow thrive in wetter conditions. To help young trees, you can check how dry the soil is by pushing a screwdriver into the ground to test the moisture. If it is difficult to push in, then it is most likely too dry and could do with being watered. However, watering is a fine line, overwatering can also be problematic for your tree. Make sure to test the soil before doing so. When planting a tree, it can be helpful to include a layer of mulch such as bark chippings. This will reduce the chances of soil compaction which is dangerous to the tree as the volume of air is reduced in the soil, stopping the growth of healthy roots.


Dying trees can not only be dangerous to yourself due to falling branches, but they can also pass harmful pathogens to neighbouring trees. Therefore, it’s important to ask a trusted tree surgeon to remove it for you before it makes the situation worse.

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