It is annoying when the beautiful splendor of roses is suddenly destroyed by fungi. An infestation usually manifests itself as differently colored spots on the leaves. But with the right care and some preventive measures, every hobby gardener can reduce the risk of disease.
Rose rust is one of the most common fungal diseases in roses
These are common fungal diseases
There are three types of fungi that are very common on roses. They are adapted to special weather conditions and therefore only occur at certain times of the year.
blackspot
Diplocarpon rosae is the cause of one of the most common rose diseases, which is favored by cool and damp weather. A disease is manifested by irregular spots on the leaves, which are gray to violet-black in color and appear radiating at the edge. Yellowish discolored leaf surfaces with reddish nuances are typical. If the infestation is not controlled in time, leaf fall will occur during the summer.
powdery mildew
This fair-weather fungus, which has the scientific name Sphaerotheca pannosa var. rosae, finds optimal conditions in humid and warm climates, which is why fungal infestation often shows up from June. You can recognize the fungus by a mealy white coating on the upper side of the leaf, which is reminiscent of a moldy lawn. With a strong expansion, the leaf surfaces curl up slightly. Buds and flowers can also be affected.
rose rust
Phragmidium mucronatum develops rust-red to orange spots, the edges of which appear dark. The more the fungus spreads, the more clearly the individual fungal foci merge with each other. Oblong spore beds grow on the underside of the leaf, in which new spores are formed and secreted. The roses respond by shedding their leaves prematurely.
What you can do about it
Since fungal infestation has a negative effect on plant health, you should address the problem as early as possible. If the disease is not very advanced, the chances of success are comparatively high.
Tips to fight:
- choose robust varieties with ADR predicate
- spray regularly with fungicides
- Combination preparations act as a universal remedy
Prevent
Remove infested foliage as soon as you see the first signs of fungal disease. The spores often survive on already infected leaves that fall from the trees. You should not dispose of the plant parts on the compost, because this way the pathogens will spread further in the garden.
Water the plants directly at the base, since a moist environment between the leaves increases the pressure of infection. Irrigation is recommended for the morning hours to allow the crop to dry off during the day. Be careful not to over-fertilize the shrubs.
Treatments with plant manure have proven to be successful for many hobby gardeners. Diluted extracts from field horsetail or comfrey are suitable. Garlic broth is especially helpful against powdery mildew. As a preventive measure, you can inject these substances into the crops when the leaves sprout in spring. Repeat the action every two weeks.