Rose diseases appear primarily on the top and bottom of the leaves, but often - especially in an advanced stage of the disease - also on the shoots and buds of the roses. In the case of stem roses, the stem itself can of course also be affected.
Which rose diseases occur on the trunk and how do you prevent them?
Rose diseases on the trunk can be caused by fungi, bacteria or viruses and often appear as rot, mildew or gray mold. To combat and prevent them, a well-ventilated location, the correct planting distance and, if necessary, pruning are important.
Damage to trunks and shoots has many causes
There are not just one or two, but very different causes for the different damage patterns. Most of the causative pathogens are fungal in nature, but bacteria or viruses can also cause some diseases. However, since fungicidal diseases are more common in roses, we will limit ourselves to these in this article.
Leaf and stem rot (Cylindrocladium scoparium)
This is a rot caused by a fungal pathogen that primarily affects the leaves and shoots of the rose and can lead to their death. This rose disease only occurs due to a culture that is too wet, for example because the rose is permanently in wet or too heavy (and therefore poorly ventilated) soil. The fungus can penetrate into the roots of the plant, which is why it is essential to act quickly: As a rule, only severe pruning and moving the rose to a more suitable location helps.
Powdery and downy mildew
Both types of mildew generally attack not only the leaves but also the shoots of the rose. In the case of powdery mildew, the buds and flowers can also be affected if the infestation is advanced. Both diseases - no matter how different they may be in their causes and appearance - are primarily caused by a poorly ventilated location. Ergo, good ventilation through pruning and maintaining the planting distance helps for prevention, and the roses should also be sprayed preventatively with plant strengtheners (€83.00 on Amazon).
Grey mold (Botrytis cinerea)
Greyish fungal growths on the leaves, buds and primarily young shoots, which often form brown, dry spots and appear “dried out”, are a sign of an infestation with botrytis, also known as gray mold. This only occurs in very humid summers or when there is high humidity; its development is also promoted by over-fertilization, especially with nitrogen. Infected shoots must be cut back to he althy wood.
Tip
Small orange-red, calloused spots that appear on rose shoots in spring are harbingers of rose rust, which eventually also attacks the leaves in summer.