A gardener's life would be so beautiful if it weren't for this powdery mildew. Hardly a growing season goes by without it spreading to beloved plants. Powdery mildew does not spare even a tree as strong as the oak. Do we need to worry about them?

A powdery mildew infestation can be recognized by the white coating on the leaves

Oak is food for fungi

Powdery mildew is a fungal disease that robs the leaves of oak trees of nutrients but does not penetrate the tree itself.

  • only young leaves are infected
  • within 3 weeks after sprouting

The so-called Johannistriebe are particularly affected. The leaves die off on affected shoots, often even the entire shoots.

conditions conducive to disease

The mycelium does not spread every year and not always to the same extent. The following weather conditions favor an explosive multiplication 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 English oak, is one of the oak species that is most frequently attacked by oak powdery mildew in this country. The sessile oak could also do so well because it produces fewer locust shoots.

Even old oaks are not resistant to this fungal disease. Their leaves and shoots can be so severely affected that the tree looks like a gray old man from afar.

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 powdery mildew from tree to tree and contribute to its spread.

Control of oak powdery mildew

The enormous potential for spreading made oak powdery mildew a dreaded disease in forestry when it acts in combination with other diseases and pests. In order not to endanger the wood yield, fungicides are usually sprayed.

With an oak tree in the garden, there isn't much that can be done to combat it. In any case, this disease is to be regarded as a "cold" that cannot really knock down an otherwise healthy plant.

tips

Heavily 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 the oak powdery mildew. Some ladybug species have actually chosen this fungus as their food.

Category:

Trees