Super remedies that will get rid of black spots on rose leaves

The beauty of rose bushes can be marred by the appearance of unsightly spots on the leaves. These spots can be brown, white, yellow, red, or rusty, and in all cases indicate health problems with the plant.

Black spot is a fungal disease whose symptoms most often appear in the summer. It not only significantly reduces the decorative appearance of rose bushes, but can also interrupt the flowering of roses.

Causes of black spots

Black spot on roses is caused by the fungus Marssonina rosae. The pathogen spreads by spores and becomes active in warm, humid conditions. Spring is the most favorable time for the fungus to develop. The disease rarely appears during dry, hot summers.

Bushes growing in low-lying areas or surrounded by dense plant growth in flower beds are particularly susceptible to the disease, as these factors impede normal moisture evaporation after precipitation and irrigation. Fungal development is also facilitated by: insufficient light or nutrients for roses; potassium deficiency, excess nitrogen, and heavy and acidic soils are particularly critical.

Symptoms and course of the disease

The disease doesn't manifest itself immediately; the first signs of damage appear about a month after the fungus has actively developed. The exception is warm and humid summers; at temperatures around 30°C, the disease becomes noticeable within 10 days. On average, black spot on rose bushes is most likely to be detected by mid-summer.

The disease spreads from the bottom to the top of the bush. Dark brown spots with a yellow border appear on the leaves and shoots. As the disease progresses, other symptoms develop:

• the spots become black and increase in size;
• curling and yellowing of leaves is observed;
• falling of leaves from bushes;
• slowing down and stopping of shoot growth;
• poor flower formation, even to the point of cessation of flowering.

Treatment of black spot

Control of black spot involves pruning affected parts of the bush, treating plants with antifungal agents, and taking preventative measures to slow the growth of the fungus.

Timely spraying of roses with folk remedies usually produces positive results, while in the later stages of the disease, chemical fungicides are recommended. It's important to note that once the first symptoms appear, the disease progresses very quickly.

The most powerful folk remedies:

1. Bordeaux mixture. Dissolve copper sulfate and lime in small amounts of water in separate buckets, using half the volume of copper sulfate as lime. Dilute the copper sulfate with hot water, and the lime with cold water. Mix both solutions thoroughly, and add cold water to each until both buckets have equal volumes. After mixing, pour the copper sulfate solution into the container with the lime solution and mix again. The amount of water is determined by the desired concentration of the solution. A 1% solution is typically used to spray rose bushes against black spot. This means, for 10 liters of water, use 100 g of copper sulfate and 200 g of lime, and make 5 liters of each solution. Apply Bordeaux mixture 2-3 times, with a week or ten-day break between applications.
2. Colloidal sulfur. Dissolve 30 g of sulfur in a bucket of water. Spray the rose bushes with the solution three times, 10 days apart.
3. Horsetail decoction. You can use fresh or dried horsetail per bucket of water. For the former, use 1 kg, while for the latter, use 150 g. Let the horsetail steep for 24 hours, then boil for half an hour. After cooling, strain the liquid and dilute each part of the infusion with 10 parts of clean water.
4. Nettle infusion. Fill a bucket halfway with fresh nettle leaves, stems, and roots (but not flowers or seeds) and add a bucket of boiling water. Let the infusion steep for at least two days, stirring occasionally to promote fermentation.
5. Liquid manure. It is recommended to use rotted cow manure. Add one part to two parts water and leave for three days. Then strain and dilute the infusion with twice as much water. Apply three times every two weeks.
6. Dandelion infusion. Chop 1 kg of roots and green parts of the plant and add 10 liters of water. After 24 hours, strain the mixture and use it for spraying and watering bushes (to kill fungal spores hidden in the soil). Apply three times, 7 days apart.
7. Onion peel infusion. Take 100 grams of onion peel and pour half a bucket of cold water over it. After 24 hours, strain the infusion and dissolve 5 grams of soap in it. Spray roses with this infusion three times every 10 days.
8. Ash. Wood ash is used in dry form to dust bushes against black spot.

Prevention

Preventive measures for black spot include:

• providing roses with suitable growing conditions;
• compliance with annual sanitary measures;
• Preventive treatments in case of risk of disease.

Growing conditions

Prevention of black spot in roses begins with choosing a planting site for the bushes and planning the flower bed.

Culture requires:

1. Sun. Roses should be planted in sunny locations where they can receive adequate light throughout the day. This will also benefit flowering and the overall health of the bushes.
2. Slightly acidic soil. When planting in highly acidic soils, liming is necessary: ​​add 250-500 g of dolomite flour or 150-250 g of lime.
3. Space. Maintaining distance between bushes prevents the rapid spread of the disease. Also, avoid surrounding bushes with dense walls of other plants—the fungus is more likely to appear where air circulation is restricted.
4. Good nutrition. Roses need to be fed during the growing season, during and after flowering. Provide phosphorus and potassium, and don't forget about micronutrient fertilizers, but exercise reasonable moderation in nitrogen feeding.
5. Crop rotation. It's best not to plant roses in areas where roses have already grown. Planting should only take place five years after other crops have been grown in the area.

Planting hygiene

In spring and autumn, it is necessary to carry out a number of sanitary measures aimed at reducing the risk of disease in roses.

1. It's recommended to remove dead and damaged branches twice a year: when preparing the bushes for winter and after uncovering the roses in the spring. If necessary, thinning pruning should also be performed.
2. In the fall, before placing the roses under cover, you need to clear the bushes of any remaining foliage.
3. Since the spores of many fungi, including those that cause black spot, overwinter in the soil, the soil under roses should be treated with a 0.01% copper sulfate solution before covering the bushes and immediately after removing the protection in the spring. It is recommended to alternate this solution with a ferrous sulfate solution.
4. In autumn, you can also treat the bushes with Bordeaux mixture or a solution of copper sulfate at a concentration of 3%.
5. In spring, it's recommended to spray roses once with Skor, Profit, Ridomil Gold, or Strobi when the leaves emerge. An alternative is two sprays with biological products, such as Fitosporin-M, performed a week apart.
6. Throughout the season, it is necessary to remove weeds from the flower bed that thicken the planting.

Processing bushes

If the spring or summer is rainy and warm, it's best to take extra precautions against fungal diseases. Regular weekly treatments are recommended throughout the season:

1. Tobacco infusion. Use 500 g of dried and finely chopped tobacco leaves per bucket of water. Pour boiling water over the leaves and let sit for 5 days. Strain the infusion before use.
2. Garlic infusion. Take 200 g of crushed garlic cloves and pour a liter of warm water over them. After 5 days of steeping, strain the solution and add 1/2 cup per bucket of water.
3. Wood ash. During the rainy season, ash should be scattered around the trunks of rose bushes.

Resistant varieties

The least resistant to black spot are varieties of tea, polyanthus, and climbing roses. Avoid planting them if conditions are favorable for the fungus. The most resistant to black spot are rose varieties with glossy leaves—their thick skin is too tough for the fungus to penetrate.

Among the most resistant varieties we can note:

• "Grande Amore";
• "Baronesse";
• «Quadra»;
• "La Perla";
• Leonardo de Vinci;
• "Memoire";
• Sebastian Kneipp
• "Nostalgie";
• "Resonanz".

Providing roses with proper care is crucial in the fight against black spot, as the fungus primarily attacks weak and weakened plants. If, for some reason, roses are at risk, measures should be taken to restore their resistance to adverse factors without waiting for the disease to appear. This can be achieved by introducing a special fertilizing regimen (increased potassium intake), watering the bushes with growth stimulants, and using products to strengthen the roses' immune system.