There are many stressors, which affect trees and put them under immense pressure. And even though one single issue can contribute to poor tree health, in most cases there are several causes at play, which impact its poor health and condition.
It pays to be prepared with some knowledge on what the most common symptoms of issues on trees are. That way you can adequately take steps to ensure that the plants and trees affected are preserved and the issue is minimised.
- Damage to the leaves – leaves are the natural diet for a variety of woodland creatures. With little damage on them, there is no immediate danger to the tree. There is hardly any single leaf without some leaf damage, which doesn’t prevent vigorous and healthy growth of the said tree. However, some pests and diseases can contribute to serious issues within the leaf or at its edges and maybe even the complete loss of leaves. One of the most widespread pests is horse chestnut leaf miner, which is a tiny insect that feeds on horse chestnut leaves. As a result, leaves acquire some brown colouring and see-through patches, which can damage the tree. Sawfly larvae also cause significant leaf damage. They are like caterpillars, which develop into flies, and not butterflies. Small trees are particularly vulnerable to them, as the insects can completely strip them. If damage occurs during the first flush, then the tree can recover. The Alder leaf beetle is another example of an insect that can affect tree leaves. It feeds on the leaves of the common alder and deciduous trees.
- Wilting and yellow leaves – this is another sign of tree stress, the risk for which can be reduced by choosing the right tree for the site. The tree may have some sort of disease, be it a bacterial one or a fungi-based one. Paying attention to which trees are impacted is important because a lot of diseases are species-specific. For example, ash dieback impacts ash trees and Dutch elm disease is mostly present on older trees. Cherries are also prone to showing disease symptoms, with leaves looking wilted and brown.
- Bleeding cankers – ‘bleeds’ on the trunks of trees are a sign of stress. There are many contributing factors, such as drought, pollution, freezing and waterlogging, in addition to some diseases. A common pathogen responsible for bleeds is the Phytophthora species, which is fungal-based. It blocks the water transport system of the tree, which in turn leads to bleeding cankers on the trunks. Bacteria can also be responsible for bleeding cankers. For example, Horse chestnut trees are often at risk from the bacterium Pseudomonas syringae. Small holes in the leaves often accompany the black patches of bark that appear on the trunk. A professional arborist may be the best bet for identifying the issue and providing a solution.
Sometimes, it is all about checking the location of the tree. Trees should be planted in the right space, or else they can struggle. Oak, yew, whitebeam, juniper and goat willow do well in slightly drier soil, whereas alder, willow and alder buckthorn do well in wetter conditions. If a tree is struggling, it may have to do with the moisture levels of the soil. If the soil is dry, then some watering is in order, though you need to be careful not to overwater the area. Water stress is often a cause for damage.