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Despite good care and an optimal location also robust rose varieties occasionally get sick. In addition to fungal diseases such as blackspot, powdery mildew and rose rust roses are not immune from pests. Whether rose cicada, aphids of the rose-leaf wasp, there are some rose pests that can neatly add to your beloved rose.
To prevent rose diseases and rose pests
Fungal diseases on roses such as blackspot, powdery mildew or rose rust, but also an infestation with pests, can be reduced to a minimum with the right choice of location and good care. Good places for roses are sunny, airy areas in the garden with loose, humus rich soil. Make sure that the plants are nourished in a balanced way and that they are watered well in dry periods. Sufficient planting distance between the shrubs is also important, so that diseases and pests can not easily spread to the neighboring plants and dry the rose petals after rain showers quickly.
An important prevention is also the correct choice of variety: If possible, plant roses with ADR-predicate, because they have been tested by the experts of the "General German Rose New Test" (ADR) for several years on their robustness and resistance to fungal infections and found to be good.
The most common rosacea diseases
The blackspot (Diplocarpon rosae) is the most common rose disease. It occurs particularly strongly in years with cool, damp weather. The diagnosis of the star soot is very simple: Affected leaves have differently sized and irregularly shaped, gray-black spots with radiating edges. In the vicinity of the spots, the rose petal is usually yellowish or gelbrötlich discolored. Heavily affected roses shed a large part of their foliage during the summer and can be greatly weakened by the fungal disease. The mushroom hibernates on the leaves on the ground.
Already at the first signs of infestation you should treat your roses with a suitable fungicide (fungicide). For example, Rose Mushroom-free Saprol, Mushroom-free Ectivo and Duaxo Roses are fungus-free against the blackness of the stars. It makes sense to use three treatments at intervals of seven to ten days each. Also carefully remove any fallen leaves from the bed because they may reoccur in the next year.
Star soot (Diplocarpon rosae)
If your roses were already infected in the previous year, preventive treatments are recommended starting with the leaf shoot. Many hobby gardeners have made good experiences with home-made herbal preparations such as horsetail broth, comfrey broth and garlic broth. These are also sprayed several times on the leaves at intervals of about two weeks from the leaves.
On roses, both the real and the downy mildew can occur. But powdery mildew is much more common. It is a so-called fair weather mushroom, which spreads especially in hot and humid weather. Therefore, it is unlikely that an infestation will occur before June. Symptoms of powdery mildew are a whitish, moldy fungus deposit, which occurs mainly on the leaf tops, but can also affect the flower stems and the buds and sepals. On the undersides of the leaves is usually a slightly weaker infestation. Incidentally, you should not compost the foliage-infested leaves, because the fungus forms permanent spores that can still be active next year. However, it is not as infectious as the leaves which are infested with blackspot and rose rust.
Powdery mildew (Sphaerotheca pannosa var. Rosae)
Powdery mildew (Sphaerotheca pannosa var. Rosae) mainly attacks roses, which are too well in the feed, because their mastigen, soft leaves offer little resistance to the fungus. Therefore, use nitrogen-rich fertilizers sparingly. Early, repeated treatments with plant tonics such as NeudoVital or Horsetail broth reduce the risk of infection. Preventative treatments with environmentally friendly sulfur preparations such as net sulfur WG or mildew-free cumulus are urgently recommended for mildew-prone rose varieties. In existing infestation, the effect of the sulfur-containing preparations is usually no longer sufficient to prevent the spread of the infection. A good effect, however, show the fungicides mentioned in Sternrußtau.
Rose rust (Phragmidium mucronatum) usually causes numerous, yellow-orange to rust-red spots on the upper sides of the rose petals, some with dark edges.In case of heavy infestation, they merge into one another and form elongated spore bearings on the undersides of the leaves that protrude from the leaf surface. From the spore camps first yellow, later dark spores escape, which are spread by the wind and can spread to other rose petals. In heavy infestation, the roses throw off their leaves as in the blackspot.
Rose rust (Phragmidium mucronatum)
Rosenrost spreads mainly in the presence of moisture - so you should ensure that your rosary can be well ventilated by the wind. In particular shrub roses must be regularly lighted so that the crowns remain loose and airy. You must remove infected fallen leaves immediately, because the old leaves harbor the winter spores, which can be re-infected next year. Against rose rust, the preparation vegetable-mushroom-free Polyram WG with repeated use at intervals of seven to ten days, the best effect. However, the remedies mentioned in the Sternrußau are also very effective and usually stop the further spread of the disease.
The most common rose pests
An unpopular garden visitor to roses is the aphid. Among the numerous species of aphids, the Great Rose-louse (Macrosiphum rosae) as a rose pest is of great importance. In an infestation sit about three to four millimeters green animals on young shoots, flower buds and leaves of the affected plants. Aphids but sticky honeydew exudates from which the respective plants suffer greatly. Due to the high propagation rate of the rose pest, explosive mass multiplication can occur, especially in warm weather.
Great rose aphid (Macrosiphum rosae)
Only use bee-friendly products to fight it, as the beneficial bees also fly on non-flowering roses to nibble the sugary honey from the leaves.
The rose-leaf wasp (Caliora aethiops) lays its eggs on the underside of the rose petals from spring to summer. The eggs hatch up to ten millimeters in size, snail-like, yellowish-green larvae. The young offspring damage the infested roses mainly by eating on leaves. Due to the so-called window damage, the animals damage the plants so enormously that usually only the leaf veins remain skeletal-like or the thin, colorless leaf upper and lower sides.
Damage and larva of the rose-leaf wasp (Caliora aethiops)
The full-grown, shiny black animals fly from the beginning of May in the gardens and are about 4.5 millimeters long. After successful oviposition, the new generation of larvae finally migrates to pupation and overwintering in late summer - the cycle begins again.
The rose clover (Edwardsiana rosae) is a three-millimeter greenish pest. The females lay their eggs in the autumn in the cracks of the bark of young rose shoots. From about mid-May, the next generation will hatch, which will develop into a fully-grown animal in the same summer. Rose cades sometimes switch to fruit trees, shrubs or strawberries to later lay their eggs. Usually follows until October a second generation of the Rosenschädlings. Especially roses in warm locations are more often affected by infestation.
The punctures of the rose cicadas are clearly visible here
They recognize an infestation of numerous, tiny whitish to yellowish punctures on the leaves of the roses. On the underside of the leaves, the greenish yellow larvae and the fully grown cicadas gather themselves. When approaching the plant the animals usually jump on. In the case of heavy infestation with suction damage, the leaves may be thrown off. Sometimes the hobby gardener then also damages the bud. Prevent beneficial insects such as predatory and leaf beetles and spiders. In addition, a pruning of young shoots in the fall offers.