Roses have had the image of the sensitive diva for a very long time, although this is no longer the case with modern breeds. Many new varieties are very resistant to the well-known rose diseases, but of course not completely immune to them. You can further strengthen the natural resistance of the plants by paying attention to a suitable location and good care. The choice of variety is just as important: roses with the so-called ADR seal are proven to be particularly robust and long-lasting.
Rose rust is one of the most feared rose diseases
Harmful images and antidotes at a glance
If you notice any abnormalities on the leaves, trunk, shoots or flowers, it is important to act as quickly as possible. If the gardener intervenes in good time, many infections can be contained right from the start, so that no lasting damage to the plants is to be feared. For this reason, you should regularly check your roses for possible signs of damage and react appropriately if the disease occurs. To make this easier for you, we have briefly and concisely described the common rose diseases.
chlorosis
Chlorosis is mainly seen in spring when the rose petals are pale yellow in color and only the leaf veins initially remain green. In addition, the rose grows poorly and develops only a few flowers. In most cases, the cause lies in an iron deficiency, i. H. if the uptake of the important nutrient from the soil is impeded. This can be done, for example, by liming the roses. Less often, a lack of nitrogen (in the case of incorrect or insufficient fertilization), waterlogging or frost damage to the wood cause the symptoms. The chlorosis can be eliminated by spraying iron or foliar fertilizer and feeding the plants with settled compost, horn shavings (€32.93) or manure. Prevent chlorosis by regularly loosening the soil to aerate it, fertilizing the roses in a balanced way and also watering them when they are dry.
powdery mildew
Powdery mildew on roses is caused by the fungus Sphaerotheca pannosa var. rosae and occurs primarily in warm, humid weather when the rose petals no longer dry quickly. On the surface of leaves, shoots and buds there is a white, floury and easily wiped coating; the leaves are also reddish in color and deformed. The affected areas of damage continue to grow, but only poorly; Buds don't open at all. Powdery mildew can be combated quite reliably with an old household remedy: Spray whole milk diluted with water several times at intervals of several days (ratio 1:10). You can also prevent this fungal disease by choosing resistant varieties, fertilizing the roses in a balanced way and also paying attention to an airy location. Plants should be cut back heavily in spring.
Wrong mildew
The harmful fungus Peronospora sparsa causes the so-called downy mildew, which mainly occurs in late summer and autumn and as a result of strong temperature fluctuations. On the underside of the leaf there is a gray-white lawn of mould, while on the underside there are brownish to purple spots. These initially appear mainly on young leaves, but spread quickly. The affected leaves wither and are eventually shed. In the event of an infestation with downy mildew, you should definitely collect and destroy all leaves, the soil can be disinfected with field horsetail broth. The disease can be prevented by placing the roses in an airy location, leaving enough space between the individual plants and thinning them out regularly.
bark burn
Elongated, reddish-brown spots, primarily around the eyes on last year's unripe shoots, are not only an indication of possible frost damage, but can also be traced back to bark blight. This rose disease is also caused by a harmful fungus and can only be combated by severe pruning in spring. Spraying with green copper (available in specialist shops) also helps, which should be carried out in winter. Prevent bark burn by giving the roses a balanced diet, aerating the soil (loosening the soil) and supplying the plants with potassium magnesium in August.
rose rust
Rose rust, caused by the harmful fungus Phragmidium mucronatum, is one of the most common rose diseases. It mainly occurs in humid summers and is characterized by yellowish to reddish spots. Rust-red and dusty spots can be seen on the underside of the leaves, which turn black in winter. This is the winter spore store from which the disease breaks out again the following spring. Rose rust primarily affects roses on loamy and compacted soil, which is why loosening the soil and mixing in sand and compost is a good preventive measure. Affected leaves should definitely be collected and disposed of, while the rose can be strengthened by treating it with horsetail broth.
blackspot
Black spot, which mainly occurs in late summer and is caused by the harmful fungus Diplocarpon rosae, is also one of the more common rose diseases. It first appears as dark spots with star-shaped edges on the upper side of the leaves; later the leaves turn yellow and fall off. Typically, the leaves growing close to the ground are attacked first. Collect the infested leaves and disinfect the soil with field horsetail broth. It also helps to put garlic cloves in the ground or plant garlic around the rose. To prevent this, choose resistant varieties and plant them in an airy location. Be sure to keep the recommended planting distances and avoid over-fertilizing with nitrogen.
ring spot disease
The ring spot disease caused by the harmful fungus Sphaceloma rosarum occurs mainly in midsummer and on densely leafy varieties. Warm, humid weather promotes the development of the disease. Typically, the center of the round, reddish spot on the leaf surface dies off, leaving gray with a black border. You can prevent this disease by providing an airy stand, giving strengthening agents (such as field horsetail broth) and removing infested leaves early.
tips
Before using plant protection products, please seek extensive advice from a specialist dealer. When using, please strictly follow the recommendations given by the manufacturer, especially with regard to the dosage.