Powdery mildew on maple - Acer campestre

A white, mealy coating forms on young leaves and shoots shortly after budding. The affected leaves stand up steeply, remain bent backwards, curl up and gradually dry out from the edge. Whole shoots can wither down to a leaf cluster with small, stunted leaves at the shoot tip.

In addition to the white fungal coating, purple-reddish discolorations are sometimes visible on the leaves.
If the inflorescences are infested, the flowers are no longer fully developed, the petals remain narrow and turn green.
Severe infestation can also result in fruit infestation in susceptible varieties.

A whitish coating, which can also be gray, spreads over the leaves.

The fungus penetrates the inside of the leaf in spring. The spores through which it spreads are usually only formed in summer within the white coating.

The affected leaves must be removed and the bonsai must be treated with a powdery mildew agent. In the following spring, a prophylactic treatment with another powdery mildew agent should be carried out during the new shoots in spring.

Caution: After treatment, clean the tools thoroughly with spirit, otherwise the spores will be transferred to other bonsai.