What tree disease is it? The most common diseases and what to do about them

What tree disease is it? The most common diseases and what to do about them

The most common tree diseases

Trees can be attacked by microorganisms and thus become ill or suffer from an unsuitable location, too much or too little moisture and a lack of nutrients. In the event of a non-parasitic disease, however, the trees are weakened and as a result can no longer adequately defend themselves against fungi, bacteria or viruses. Another illness is therefore often the result.

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Wood-decomposing tree diseases

Typical tree diseases can affect the leaves, but often also the wood. In particular, wood-decomposing fungi pose a danger. Often these are invisible fungi, although species with pronounced fruiting bodies such as honey mushrooms or tinder fungi are not uncommon.

Red pustular disease

This is a weak or wound parasite that mainly affects deciduous trees. Fruit trees such as plums, cherries, apricots and all pome and nut fruit species are often affected, but also ornamental trees such as maple, robinia, hornbeam and box. The fungus develops mainly on dead wood as well as on dead parts of living trees. From there it attacks healthy areas if it finds stumps and other wounds to penetrate.

Leaf spots

Leaf spots can have very different causes. In addition to fungi, bacteria and viruses, the stains can also be caused by cell sap-pulling or leaf-eating pests. Leaf spot diseases caused by fungi occur primarily as a result of damp weather, particularly in late summer and autumn. Infested leaves should be removed liberally, especially if they have already fallen. The various pathogens often overwinter in it, which is why such plant material never belongs on the compost.

Leaf tan

This fungal disease is a typical phenomenon of damp spring and summer weeks, which initially shows itself as small, rounded, red-brown spots on the leaves. If the damp weather continues, the spots soon cover the entire leaf. If the infestation is severe, leaves can fall. In the case of fruit trees in particular, the fruits can also be infected.

scab

Scab is also a widespread fungal disease. The infection often takes place in early spring when the temperatures are quite cool, when the spores spread by wind and rain are transferred to the leaves. Wet leaves and high humidity promote the spread. Over the summer months, new spores form over and over again, which then overwinter in the fallen leaves on the ground. Scab fungi are noticeable through brown, rounded spots that become increasingly larger.

Shotgun Sickness

Shotgun disease is also a fungal disease in which small, reddish to brown spots initially appear on the leaves. These break out later, so that the leaves with their irregular holes appear to have been riddled with a shotgun charge. If the infestation is severe, the leaves are shed.

Rust fungi

There are different types of rust fungi as they are highly specialized in certain tree species. Orange-red, reddish or purple-tinged leaf spots that mainly appear on the upper side of the leaves are typical. Infested wood should be cut back generously.

Diseases with fungal pathogens

Another fungal disease is powdery mildew, which - unlike other fungal diseases - does not need damp weather to spread. Flower, fruit and twig monilia (“tip drought”) as well as the wilt disease caused by various Verticillium fungi also occur frequently in many tree species.

Diseases with bacterial pathogens

In the case of bacterial pathogens, it is above all fire blight and bacterial blight, which occur in many trees, especially fruit trees, and can cause considerable damage here. Like fungi, bacteria penetrate the tree through wounds and other open areas and spread from here.

Typical diseases in selected tree species

The following tables provide an overview of the types of diseases that occur in certain tree species that are often cultivated in gardens. If a tree species is not explicitly named, it is a robust, less disease-prone species - which, despite its robustness, is of course not immune to infection.

Fruit trees

Type of fruitCommon diseases
AppleScab, powdery mildew, fruit tree canker, collar rot, stippling
pearScab, pear grate, fire blight
Plums, mirabelle plums, reneclodsRust, shotgun disease, fool's or pocket sickness, sharka
Peach apricotFrizziness, scab, chlorosis
Sweet cherry, sour cherryShotgun sickness, Monilia

Deciduous trees

Deciduous tree speciesCommon diseases
Maple (acer)Powdery mildew, wilt, leaf spot pathogen, leaf tan
Beech (Fagus)Leaf tan
Oak (Quercus)Powdery mildew
Chestnut (aesculus)Powdery mildew, wilt, rust, brown leaves
Lime tree (tilia)Leaf tan
Trumpet Tree (Catalpa)Wilt
Elm (ulmus)Wilt
Willow (Salix)Powdery mildew, rust, leaf spot pathogens
Crabapple (malus)Powdery mildew, shotgun disease, scab
Ornamental cherry (Prunus)Shotgun disease, scab, wilt, leaf spot pathogen

Conifers

Conifer speciesCommon diseases
Araucaria (Araucaria)Needle tan
Yew (taxus)Wilt
Spruce (Picea)Wilt
Pine (Pinus)rust
Larch (larix)Gray mold rot, larch cancer
False cypress (Chamaecyparis)Phytophthora rot, needle tan
Fir (Abies)Pine shrimp, rust, gray mold, needle tan
Juniper (Juniperus)rust
Cypress (Cupressus)Phytophthora rot

Tips

Most tree diseases can be kept in check if the crown is kept light - this way the leaves dry off faster and there is also enough light and air inside the tree crown.