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Black spots on rose leaves, like other lesions, cause weakening and help reduce budding of the plant. If measures to eliminate the disease are not taken in time, the flower may die. Overcoming spotting can be very problematic; it often happens that it spreads to all bushes. Experienced gardeners claim that it is much more effective and simpler not to treat already infected roses, but to prevent this disease annually.
What does black spot look like and why is it dangerous?
Brown spotting on rose bushes is caused by the fungus Marssonina rosae, which is transmitted during rain or through dew drops and has a detrimental effect on the crop.
The disease does not appear immediately; rose leaves begin to become covered with black spots 30 days after the development of the fungus. The only exception to the rule is humid, warm weather. At temperatures around 30 degrees, spotting can become noticeable already on the tenth day. But usually it manifests itself in full closer to July.
The first symptoms appear in the lower part of the plant and gradually spread to the top of the bush. Shoots and leaves are covered with dark brown spots with a yellow border. Over time, other symptoms arise:
- the spots begin to enlarge and become black;
- the leaves turn yellow and curl, and a little later they begin to fall off;
- shoots grow slowly or stop developing altogether;
- buds become inconspicuous in appearance or completely cease to form on the bushes.
Black spot is difficult to treat and can completely destroy the plant.
Why do black spots appear on rose leaves and they fall off?
In order for the treatment of the disease to give a positive result, it is important to correctly determine the reason why black spots appeared on the roses and they dropped their leaves. There are several reasons that contribute to the damage to bushes:
- Wet and warm weather. Leads to the activation of fungal spores, as a result of which rose leaves begin to become covered with brown spots and fall off.
- Inappropriate landing site. A thickened area or lowland promotes slow evaporation of moisture, multiplication and spread of spotting.
- Inadequate care. Late detection of provoking factors can also be the cause of the disease.
- Using insufficient or excessive amounts of fertilizer. A lack or excess of nutrients leads to the development of the disease.
What to do and how to treat black spots on rose leaves
Timely and properly selected treatment for black spot on roses (see photo of the lesion below) will help get rid of the disease. There are several ways to combat the disease, but the first thing to do is cut off and burn all diseased leaves. If this procedure is neglected, then in the new season the rose will get sick again.
In addition to destroying diseased plant elements, gardeners often resort to using various means, which are also considered very effective in the fight against black spot. Preparations can be either chemical or biological in nature, some use traditional methods.
Rose foliage with black spots must be torn off and burned
Chemicals
If the rose leaves turn yellow and become covered with black spots, they should be treated with chemicals that contain mancozeb and zinc. The most effective among them are:
- Oksihom.
- Profit M.
- Copper chloride (Cloroxed cuprum).
- Ridomil gold.
- Strobe.
Treatment should be carried out every 14 days, constantly changing the drug. This is done to prevent the fungus from developing strong immunity to it.
Treatment of the disease should be carried out until the dark spots stop growing and spreading
Biological agents
If you find yellow leaves with black spots on a rose, you can use not only chemical, but also biological means to eliminate the problem. The drug Fitosporin-M with the addition of Zircon or Siliplant has proven itself as a cure for black spotting. Before treatment, you should destroy all diseased specimens, then feed the soil with copper-containing compounds and spray the bushes with the solution. The procedure should be carried out every 5 days, preferably at least four times. In the intervals between treatments with Fitosporin, the soil around the plants should also be watered.
Folk methods of struggle
You can also fight dark spots on rose leaves using improvised means. A good folk method against infection is to spray seedlings with iodine solution. In this case, you should use the product carefully so that it does not fall on the ground. Prepare the drug by mixing 1.5 ml of iodine and half a liter of water.
Another folk antifungal remedy is a decoction of onion peels. It can be used to either spray or water a diseased plant. To prepare the medicine, take the peels of two onions and boil them in 500 ml of water.
Cow dung is no less effective against spotting. Mullein is diluted in a ratio of 1 to 20 and the culture is watered with the resulting infusion.
Many gardeners report good results after using infusions of dandelions, nettles or horsetail.
Traditional methods of combating black spotting are less effective and are more suitable as preventative agents.
How to treat roses against black spot in spring
To avoid the appearance of black spots on the leaves of roses, they should be sprayed in the spring, before the buds open. Many gardeners consider copper sulfate (copper sulfate) to be the most common and proven means for primary treatment. It is a very powerful fungicide and can only be used once per season. Diluted in a proportion of 50 g per 1000 ml.
Towards the end of spring, in May, you can additionally spray roses with Strobi. This should be done 2-3 times with an interval of 10 days.
How to treat roses against black spot in summer
The cheap product Fitosporin M can help avoid black spotting on roses. The only main rule when using it is regularity. The biofungicide will give results if it is used throughout the summer, every week (especially in August). The effectiveness of Fitosporin can be increased by combining it with Gumi paste.
How to treat roses against black spot in the fall
For successful wintering, it is also important to treat rose bushes with anti-infection agents. They can be made healthier using traditional methods (onion decoction, iodine solution) and commercially available drugs (fungicides).
In autumn, treating roses against black spot involves using Fitosporin (if the plant is not sick). Spraying should be carried out with the onset of cold nights, fogs and when dew appears. Frequency of actions – up to 4 times, every 5 days.
At the slightest suspicion of black spot infection, rose leaves should be sprayed with stronger preparations, such as:
- Topaz (topazius).
- Skor.
- Bayleton.
If the disease covers the entire bush, then it is better to use “Hom” or “Oxyhom”.
Prevention of the disease
As preventative measures to combat black spot, gardeners use the same means as in treating the disease. The only difference in the procedure is the frequency of use of the drugs.
Timely treatment of the plant
Spraying must be carried out even before black spots appear on the leaves and on the rose bush, at the onset of warm weather, after the snow has melted. At this time, the mushrooms do not have time to grow stronger and spread. For prevention, fungicides, biofungicides and compounds with copper are usually used:
- Glyocladin or mikosan-I (100 ml per 10 liters of water).
- Copper sulfate.
- Bayleton.
The first spraying of roses against black spot should be carried out in early spring
Planting varieties resistant to disease
There are no varieties that are 100% immune to rose disease - black spot. But as practice shows, the species with glossy leaves are considered the most resistant to damage:
- Grande Amore.
- Quadra.
- Leonardo da Vinci.
- Resonance.
- Nostalgie.
- Baroness.
Climbing varieties, as well as tea and polyantha varieties, are more prone to infection with black spot. You should refrain from planting such roses if growing conditions are favorable for the occurrence of the disease.
Recommendations
To prevent brown spots on rose leaves from ever appearing, it is advisable to follow these recommendations:
- Constantly change medications. Both treatment of roses and measures to prevent black spotting should be carried out with different substances.The fungus is good at adapting to life and can develop immunity to fungicides.
- Consider the harmfulness of the composition. When purchasing a drug, you should pay attention to its hazard class and strictly follow the recommendations for preparing solutions.
- Burn affected leaves. The fungus is completely destroyed only after exposure to fire; no other methods work on it.
- Carry out prevention. Every spring you should spray the leaves and bushes of roses well with antifungal drugs, monitor the evaporation of moisture from the ground, and observe the interval between plants when planting.
- Plant only healthy seedlings. You need to buy rose cuttings that are strong and uninfected, preferably in specialized stores. Before planting new bushes, it is better to try to keep them in quarantine for 1-2 months.
Conclusion
Black spots on rose leaves cannot always cause the death of the plant. To avoid sad consequences, it is important to diagnose the disease in time and take urgent measures to eliminate it. It’s better not to neglect preventive measures, regularly provide the shrub with proper care and completely prevent the development of black spotting. If infection occurs, treatment will take a long time.
