Black dots on the rose, what is it?
When growing roses, black spot is one of the most common diseases, and if left untreated, it can become a serious problem.
All cultivars are susceptible to some degree of black spot disease, but some are more than others. Hybrid tea roses, miniature roses and grandifloras are most susceptible to this problem.
Note! Black spot mainly affects young rose leaves that are 1-2 weeks old, while older lower leaves on rose stems are much more resistant to infection.
The disease on the leaves and stems of roses is caused by a fungus. Infected leaves turn yellow over time and fall off early, even before the onset of autumn. Fungal spores can overwinter on fallen leaves and then re-infect developing new foliage in the spring. They can weaken the plant, especially if the infection occurs early in the season. Young plants are most susceptible to this fungal infection as they do not yet have a proper defense system.
Symptoms of rose leaf spot
The disease is easily recognized by black spots on the foliage. They appear on the top and bottom of the foliage. From spring to autumn, dark brown blackish spots are often visible on the leaves of roses.
Also, infection can be seen on young shoots of roses, stems and even flower petals. The edges of the spots are uneven, and are surrounded by a pale yellow ring. Their size varies from 1-2 mm or more to 10 mm in diameter. Diseased leaves turn yellow after a while and fall off.
What environmental conditions favor black spot roses?
The disease spreads very easily, as it is carried by rain and wind. It can also be transmitted from plant to plant and with pruning tools if not disinfected.
Why do black dots appear on roses?
- Waterlogging and wet foliage.
- Lack of air circulation.
- temperature range in spring.
- Purchase of infected plants.
This fungus loves to thrive in moisture, and overwatering is the main reason. Fungus spores are transferred from infected leaves to undamaged ones with the help of water droplets. The pathogenic fungus (Diplocarpon rosae) multiplies and infects in humid conditions, at a temperature of about 20-25°C. However, high temperatures above 30 C limit its growth.
Proper air circulation around the plants ensures that the leaves and stems are dry, leaving no room for fungus to grow.
The fungus, having overwintered on fallen diseased leaves, re-infects the bushes during the growing season. If measures are not taken in time, the plant will lose foliage, dry out and die.
Rose of illness. How does black spot disease affect roses?
Over time, the disease makes them weak, the plant produces fewer flowers. The affected plant produces fewer flower buds. Soon, the spores of the fungus spread to all parts of the plant, which leads to growth retardation and the inability to open flowers. Rose bushes become susceptible to winter and heat damage.
The pathogen can also get into the garden if you buy infected rose bushes. When buying, you should carefully check for the presence of infection on both the upper and lower sides of the leaves.
How to deal with black spot on rose bushes?
Although this fungal disease can be very harmful to the plant, it is easy to treat. Black spots on roses require immediate attention. It is necessary to take a number of preventive and therapeutic measures. Plant varieties of roses that are resistant to leaf spot.
Remove fallen leaves regularly. The fungus overwinters in infected leaves, and these leaves should be collected and removed from the site, or incorporated into the soil.
Toward the end of winter, a thick layer of mulch is spread around the base of the diseased plant, thereby preventing fungal spores from settling.To protect against black spot avoid dense plantings of roses. Dense plantings create conditions of poor ventilation and high humidity, as a result of which the disease develops more easily, at the same time it is much more difficult to fight it.
Additional Information! In general, for all varieties of roses, roses need a sunny place, on loamy, slightly calcareous, nutrient-rich soils, where there is always a little air. Do not plant in soil where roses used to be. Roses need to form strong roots that will develop as a result of fertilization.
During the growing season, the basis of protection is the removal of fallen leaves from the area adjacent to the plants. The first yellowed leaves, which are the initial lesions, are removed from the rose bush. In addition, you should collect all fallen leaves and affected shoots at the end of winter and remove them from the garden.
Avoid excessive watering of rose bushes, and do not water them from above, since black spot develops more easily in conditions of high humidity. It is necessary to ensure that the leaves do not get wet when watering, because water favors the development of the disease in the presence of infections on the ground. In the home garden, watering in the evening should be avoided because it helps the infection to take hold by increasing the humidity at night.
Foliar spraying is recommended as a preventive measure. Fungicides effective against leaf spot diseases (Amistar, Ditan, Fundazol, Orthocid, Polyram) can be applied following the instructions on the package.
Treat young foliage in early spring, then repeat at regular intervals throughout the season. Repeated processing of foliage is justified in especially rainy, constantly wet weather.
How to treat blackheads on roses with home remedies?
For those who want to use organic preparations, baking soda can be used, which is able to change the pH level on the surface of the leaves, which makes it difficult for plants to infect the black spot fungus.
How to prepare this organic solution:
- mix one to two tablespoons of baking soda with a liter of water;
- add a few drops of dishwashing detergent to keep the baking soda on the surface of the sheet.
Spray the leaves on both sides. Repeat weekly and after every rain.
Milk mixed with water in a ratio of 1:1 and applied to the affected areas with a soft cotton pad, you can also use it as a spray.
Add vinegar and hydrogen peroxide to a liter of water in a teaspoon, mix well and pour the solution into a spray bottle. Spray foliage on affected areas. If that doesn’t work, use a copper or sulfur fungicide as directed on the label.
In addition to all these measures, it is important to remember that this disease is spread from fallen leaves and stems, so dispose of everything carefully. Always disinfect secateurs after pruning a diseased plant.