Content
- Mildew, Sternrußtau, Rosenrost - The most common leaf diseases on roses
- Powdery mildew
- Wrong mildew
- blackspot
- Rose rust
- Gray mold
- Tips
Rose rust is a dreaded rose disease
Mildew, Sternrußtau, Rosenrost - The most common leaf diseases on roses
The countless species and varieties of the genus Rosa are unfortunately very susceptible to various diseases, which is mainly favored by an unsuitable location or wrong care. More robust than many cultivated roses are only wild roses and their hybrids, whereby these representatives of the rose plants are not immune to the most common leaf diseases. These are mainly caused by fungi.
Powdery mildew
The powdery mildew, due to its increased occurrence, especially on hot and dry summer days, is also called "fair weather mushroom". It mainly attacks the leaves and young shoots and sometimes buds and flowers. Powdery mildew is caused by the fungus Sphaerotheca pannosa, although there is also a variety that only affects roses. This can be recognized by a white coating on both sides of the leaves as well as reddish discolored leaves.
Wrong mildew
In contrast to powdery mildew, the downy mildew caused by the fungus Peronospora sparsa occurs mainly on humid summer days. They detect an infestation from the dark purple to reddish brown colored leaf spots, which are brown at the bottom. At high humidity, the typical white-gray spore surface appears here as well. In addition to the leaves, the stems are often infested.
blackspot
Also the star soot (caused by Diplocarpon rosae) appears on the leaf mainly in damp weather. The rose petals first whiten or turn yellow to develop round, blackish-brown spots. These patches are initially small, but increase with progressive infestation.
Rose rust
The fungus Phragmidium mucronatum attacks roses mainly in spring and causes the quite common rust disease. This is quite good at recognizing large, orange spots on the top of the leaves. The rose rust survives until late summer, then form on the underside of leaves tiny black fruiting bodies. In these hibernate the fungal spores, and then the next spring to attack the rose again.
Gray mold
Typical of infestation with Botrytis cinerea, the gray mold blight, are reddish or brown specks on the leaf. In the further course, soft, foul spots develop not only on the leaves, but also on the shoots and flowers. The gray mold spoilage is particularly common in high humidity and in rainy weather.
Tips
Most leaf diseases on roses are caused by too much moisture and especially when the leaves are permanently wet - for example, because it has been raining for a long time or because of a wrong casting behavior.