2024 Author: Gavin MacAdam | [email protected]. Last modified: 2023-12-16 13:38
Black spot of roses is a frequent guest of rosaries. You can encounter it in any area where roses are grown, and flower growers of almost the whole world are familiar with this ailment. To a large extent, the development of this misfortune is facilitated by the combination of moderate temperatures (from twelve to twenty degrees) with rainy weather. Premature loss of leaves makes roses form new shoots that do not have time to ripen and therefore often freeze in winter. If you do not fight black spot, then roses will begin to lag behind in growth and development. And the decorativeness of the affected roses suffers decently - even single specks make the queen of flowers less attractive
A few words about the disease
Roses are most often infected with black spot at the beginning of the growing season, however, the manifestation of visible signs of a harmful disease can most often be seen only closer to the middle of summer, in the second half of it. On the upper sides of the leaves, the formation of rather large (often reaching 15 mm in diameter) rounded or star-shaped specks, equipped with yellow edges, begins. Initially, they are brownish, but after some time they become almost black. Sometimes, instead of such large spots, many small fuzzy spots appear, which gradually merge and cover the entire surface. Rose leaves turn yellow or gray-brown tones, curl and fall off rather quickly.
The specks characteristic of black spot can also form on flowers with stems. The stalks attacked by the disease become very lignified and after a while completely dry out.
Upon close examination, on the specks, you can notice barely visible "swellings" of an oblong or round shape - these are fungal sporulation.
The causative agent of black spotted roses is the pathogenic fungus Marssonina rosae. Spores of the pathogen are carried mainly with the help of water droplets, and their wintering takes place on fallen leaves and in affected shoots. And with the onset of spring, black spot begins to move upward along the stems.
The most susceptible to the ill-fated ailment are considered to be remontant varieties, as well as hybrid tea varieties with yellow flowers and pale green leaves. Climbing and so-called "wild" roses (or rose hips) are also exposed to the harmful misfortune. At the same time, different varieties of roses in different areas are affected completely differently.
How to fight
Purchasing healthy roses for planting and following basic agrotechnical rules can significantly reduce the likelihood of damaging beautiful flowers with a destructive ailment.
Roses should be planted in sunny areas, and the resulting bushes should be formed in a timely manner. With the onset of the long-awaited spring, for preventive purposes, roses are recommended to be treated with preparations containing copper ("Ordan", "Abiga-Peak", "Hom", etc.). It is best to carry out processing at the stage of blooming leaves or before flowering.
In the summer, it is extremely important to systematically ventilate the growing pink bushes, and also make sure that there are no droplets of moisture on the leaves. Infected leaves should be collected and burned. It is also necessary to eliminate weeds from the sites and cut out shoots attacked by black spot. Affected roses are recommended to be treated with Skor. The drug "Fitosporin-M" also helps well in the fight against this scourge, which is recommended to be used with an interval of ten to fifteen days before and after flowering. Also suitable is "Pure Blossom BAU", which begins to be applied immediately when signs of black spot appear, and then the treatments are repeated every two weeks. Stimulants such as "Epin", "Zircon", etc. will also be useful.
As soon as autumn comes, all fallen leaves should be removed, and the soil under the roses should be carefully dug up. Well, just before covering the queen of flowers for the winter, both the roses themselves and the soil under them must be thoroughly treated with copper-containing preparations again.
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