A gardener's life would be so beautiful if this mildew didn't exist. Hardly a growing season goes by without it spreading to beloved plants. Mildew does not spare even a tree as strong as the oak. Should we worry about them?
What helps against mildew on oak trees?
Mildew on oak trees is a fungal disease that mainly affects young leaves and shoots and is favored by high temperatures, intense sunlight and low humidity. Control in the garden is usually not necessary as it is a relatively harmless disease. However, heavily infected branches can be removed.
Oak is food for mushrooms
Mildew is a fungal disease that removes nutrients from oak leaves, but does not penetrate the tree itself.
- only young leaves are infected
- within 3 weeks of budding
The so-called St. John's shoots are particularly affected. The leaves on infected shoots die, often even the entire shoots.
Conditions conducive to disease
The fungal network does not spread every year or always to the same extent. The following weather conditions promote an explosive proliferation of the fungal pathogen:
- high temperatures
- intense sunlight
- low humidity
Because of its preference for warm and dry summers, the mildew fungus is also known as the fair-weather fungus.
Pedunculate oak is more affected
The German oak, also known as the English oak, is one of the oak species that is most often affected by oak powdery mildew in this country. The sessile oak could also do so well because it produces fewer St. John's shoots.
Even old oak trees are not resistant to this fungal disease. Their leaves and shoots can be so badly affected that the tree looks like a gray old man from a distance.
Fruiting bodies for survival
Mushrooms also have to survive until the next season, which is why they form so-called fruiting bodies with seed spores. In oak powdery mildew they have a spherical shape and are located on the white leaf cover. Depending on the ripeness of the fruit, their color is yellow, brown or black.
The fungus overwinters on the buds. Pests such as oak moths carry oak mildew from tree to tree and contribute to its spread.
Combating oak mildew
The enormous potential for spread has made oak powdery mildew a feared disease in forestry when it works in combination with other diseases and pests. In order not to endanger the wood yield, fungicides are usually sprayed.
There is not much that can be done to control an oak tree in the garden. In any case, this disease is to be viewed as a “cold” that cannot really knock down an otherwise he althy plant.
Tip
Severely infested branches can be cut off and disposed of with residual waste or, if possible, burned.
Ladybugs like this mushroom
There are creatures that are happy about oak mildew. Some species of ladybirds have actually chosen this fungus as their food.
