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Black spots on the leaves of roses: phytosanitary interventions, pruning and how to treat roses affected by scab.
Is called scab and it is among the most common diseases of roses. The most obvious symptoms of thescabthey see a progressive yellowing of the leaves of the roses with the appearance of black spots, even the flowers can be affected. Therescabit's arose diseaseof fungal origin.
The person in charge ofblack spots on the leaves of rosesis the mushroomMarssonina rosae. The most serious fungal infections occur in the presence of dew, high humidity or wrong watering that keeps the foliage wet for too long. The disease originates when, in the strong dew, the ideal development temperatures occur, ie between 24 - 26 ° C. With temperatures above 33 ° C or below 13 ° C, the fungus spreads with greater difficulty, so in winter or in the height of summer there may be a spontaneous regression of symptoms which will then return to manifest themselves in autumn or spring.
How to distinguish thescabfrom othersdiseases of roses?
Scab manifests itself withdark spots on the leaves of roses, the color is brown, blackish and sometimes tending to purple. The spots are almost round in shape and have a jagged margin. The black spots on the leaves are about one centimeter in diameter. Attached leaves turn yellow and deteriorate prematurely and at the same time cause a strong weakening of the plant which in the long run could stop the blooms.
How to care for roses
The best way to get rid of the fungusMarssonina rosaeconsists in acting promptly: as soon as you see the first black spots on the leaves of the rose, remove them!
Cut off the affected leaves and remove them from the garden because they are infested with the fungus. At the time of irrigation, avoid wetting the foliage and follow a treatment with a good copper-based antifungal.
Treatment should be performed every seven to ten days until the symptoms have completely disappeared. The infection should be treated with a copper-based preparation such as Bordeaux mixture-20 or copper oxychloride-20. Both phytosanitary products indicated are allowed in organic farming and very effective against the Marssanina rosae fungus. For dosages and dilutions rely on the instructions on the label.
To avoid recurrence, preventive treatments are recommended when humidity levels increase and temperatures are optimal for the development of the fungus.
Copper oxychloride is a very useful antifungal in the garden and in the vegetable garden. It can be used for the prevention and treatment of various diseases of fungal origin.
They can be used both on ornamental plants (flowering plants), and on vegetables and fruit plants (vine, olive, citrus, horticultural plants ...). It is recommended for the treatment of black spots on rose leaves (Punctuation) as well as for many other diseases: Copper Oxychloride is the most used fungicide to treat Downy mildew, Monilla, Corineo ... The powder should be diluted and then sprayed on the plant to be treated. Even if the diseased plant is unique in your rose garden, it is advisable to also intervene on healthy plants in order to prevent. This fungicide is quite affordable: a one kilogram pack of copper oxychloride, on Amazon is offered at a price of 15.90 euros. For all information, I refer you to the official product page: Copper Oxychloride on Amazon.
Pruning of roses
Between autumn and winter, to prevent the appearance of rose diseases and stimulate good flowering, pruning is recommended. Before pruning the roses, sterilize the blades of the scissors using ethyl alcohol.
Remove dead, broken and older branches first. Always cut at the height of a bud facing the outside of the shrub or near healthy wood. With the pruning of the rose all weak and thin branches must be eliminated. Do not be afraid to thin out and in order to better aerate the plant, cut off the branches that intersect each other.
If you cut a branch with a diameter of 3 cm, brush the cut surface with healing putty.
For the others diseases of roses: bad white of the roses.