There are different black spot pathogens that affect different plants. For example, roses are affected by the fungus Marssonina rosae that causes black spots to form on their leaves, while the pathogenic bacteria of the genus Syringae affect lilacs.
Special features of black spot
If a plant is affected by black spot, this can be understood by the dark brown, almost black spots that form, either the edges or the middles may be light. Sometimes there are oblong or circular swellings formed on the spots. As a rule, the manifestation of disease symptoms is observed at the beginning of summer.
If the disease develops very actively, it can affect vast areas of foliage, causing it to turn yellow and fly off early. As a result, branches become bare and the bush becomes weaker, its development worsens, and it blooms poorly and produces a poor harvest. Water, wind, and pests help spread the infection. The disease develops most actively during long rains against the background of lack of potassium in soil and low air temperatures. The disease may be triggered by mechanical stress on the leaves or bark.
Treatment of black spot
Before choosing how to treat a diseased plant, you must be sure that it is affected by black spot. Remember that the disease has two forms, for example: If the signs of such a disease were found on tomatoes or peppers, then you are dealing with a bacterial black spot, and if the disease affects the rose, in this case it is fungal. But general methods of dealing with black spot of any nature have been developed, the primary task of which is to strengthen the health of the plant. This means that there are a number of certain measures that can protect various crops from the development of the infection.
Before sowing seeds or planting seedlings of a particular crop, you should not be lazy and choose the most suitable place for this.
This means that it is better not to plant shady crops in a sunny place and not to plant plants which need a lot of bright light in the shade. If you ignore these rules, this will lead to a weakening of the crop, making it less resistant to pests and diseases. Even pay special attention to the quality of the soil, before planting any culture, you need to carefully prepare the site and the soil, so it corresponds to the agronomic requirements of the plant. Also experts advise, for cultivation, choose those varieties that are highly resistant to pests and diseases. Still it will be very good if the variety is adapted to the conditions of the region where it is going to be grown.
Don't neglect pre-sowing preparation of seeds and be sure to disinfect them, especially if the seed was purchased in a store that is not trustworthy. Planting crops at the times and according to the schemes recommended by experts, keep in mind the rules of cultural agrotechnics, systematically carry out preventive treatment of pests and diseases, as well as properly and timely fertilize and water the plants. After harvesting, be sure to clean the area of plant debris and don't forget to tidy up the soil.
How to treat roses for black spot
Black spot on vegetable crops
Tomato black spot
The bacterium Xanthomonas vesicatoria is the causative bacterial black spot, which affects tomatoes grown both in the greenhouse and outdoors. Seedlings and young bushes have watery, dot-shaped spots on the leaf surface that increase to 0.
1-0.2 cm with time, and their edges gradually become yellow. On adult shrubs, the spots are usually located on the edges of leaf plates, and also on the surface of petioles and shoots. Fruits are also affected by spotting, with convex dark-colored dots with a watery rim forming on their surface. Over time, they increase in size to 0.
6-0.8 cm and become ulcerated. The pathogen can remain on plant residues and seeds for a long time, so do not forget to disinfect the seeds before sowing.
The pathogen enters the above-ground parts of the bush through breaks, cracks and various mechanical damages. Infection then spreads rapidly through the tissues, and 3 to 5 days elapse between the moment the bush is infected and the first symptoms appear.
On the surface of fruits, spots appear later, and bushes nearby the diseased plant become infected with black spot after about 15 days. The disease is most active at air temperatures above 25 degrees, but if it's cooler, the infection will not go anywhere, but will only slow down its development. Also, this bacterial disease begins to develop actively when air humidity rises to 70-75%, but only if the above-ground parts of the bush get wet. Under these conditions, the development of the disease is very rapid.
The causative agent of the spot disease persists as long as there is a food source on the site.
If the area is thoroughly cleaned after harvesting, the pathogen will die within 4-5 weeks. Currently, there are no tomato varieties that are resistant to black spot. However, it has been observed that tomatoes that are not affected by fungal diseases quite rarely fall ill with black spot.
Preventive measures, such as seed pre-sowing preparation consisting of seed dressing, play an important role in controlling the infection. Seeds can be disinfected in various ways:
- Seeds are poured into a solution of a fungicide and pulled out after 1 hour.
- Thirty minute treatment in a solution of pink manganese.
- Prepare a solution of Trisodium phosphate (12 grams of the preparation per 100 mg of water) and immerse the seed in it for 1 hour. Then it is rinsed well under running water or in a sieve for 20-30 minutes.
- For three hours soak the seeds in very warm water (about 60 degrees).
These uncomplicated methods will help get rid of the infection that is present on the surface of the seed.
However, to get rid of the internal seed infection, you will need another method. To do this, the seed material is dipped into a solution of the biological fungicide Planriz (1%) before sowing. Tomato seedlings are treated twice with a solution of Phytosporin-M, Bactophyte, Planriz or Gamair just before planting in the open soil. Phytolavin is very effective for treating tomatoes, as it is able to kill the pathogens of bacterial black spot, apical rot, bacterial cancer, and other diseases.
After planting tomatoes in the open ground, they should be systematically sprayed with a solution containing copper as a preventive measure.
For example, you can use Oxyhom, Hom, a solution of Bordeaux mixture (1%) and other products of similar action.
Black pepper blotch
The causative agent of black bacterial blotch on sweet pepper and tomato is the same: Xanthomonas vesicatoria. The infection most often affects the young parts of the bush, resulting in the appearance of pinpoint watery spots on the leaves, fruits, shoots, seedpods and petioles. As the disease progresses, the spots become black and their shape changes to round or angular. These black spots, which have pale yellow edging, are about 0.
1-0.2 cm in size. The spots spread along leaf veins, and yellowish necroses with dark borders are formed in their midst. On the surface of fruits, convex points of black hue, surrounded by watery fringe, are also formed at first. As the disease progresses, the spots increase to 0.
6-0.8 cm and they become rotting ulcers. Peppers should be protected from black spot and treated with the same methods and remedies as tomatoes.
Black spot on fruit crops
Black spot on grapes
Grape black spot is also called fomopsis, either bark cracking or escoriosis or shoot dieback, and its causative agent in this case is the fungus Phomopsis viticola. Its first symptoms appear in June on the surface of annual shoots' nodes: oval or round spots of black or brown-black color are formed on them; they look like swollen tissue with a center of necrotic cells in the middle.
Over time, the number of spots gradually increases and they begin to connect to each other, forming patches that open in the middle. On the surface of the edges of darker-colored spots, cork tissue is formed, which looks like scabs. Most often, only the first 6 or 7 internodes of the stem are affected by the blotch. Leaf blades at the very bottom, bunch crests, tendrils, and flowers are affected by the infection. Necroses have dense light-colored fringes on leaf plates, and tension of tissues is observed, making leaves look curly and tearing in some places, resulting in holes.
The foliage turns yellow earlier than it should. Because the leaves are deformed and holes appear on them, photosynthesis is weakened, and it may happen that in one-year stems in the lower internodes most of the buds die. Diseased fruits turn dark violet in color and taste unpleasant, one-year wood affected by the disease becomes grayish-white.
Spreading of black spot pathogen is promoted by: rain, dew, wind and pests. And it can enter the bush through stomata or mechanical damage.
A diseased plant becomes less resistant to frost, and if you do not start to treat it, the grapes will die after 5 or 6 years. Experts advise you to choose varieties that are resistant to black spot, for example: Cabernet-Sauvignon, Liana, Traminer, Tavrida, Spark, Riesling, Bastardo Magarachsky and Estafeta.
If you notice signs of black spot disease on grapes, you should start fighting it immediately. The peculiarity of this disease is that the fungus mycelium is located very deep in the tissues, so treatments of the plant with fungicide preparations will be ineffective. However, by treating plants with Nitrafen or DNOC, you can destroy both fruiting bodies and fungus spores.
That is why it is so important not to forget to conduct timely treatments to prevent fungal diseases, as this will help protect your vineyard from black spot.
Preventive treatments of bushes with Efal, Euparene, Mikal or Bordeaux mixture (1%) solution are conducted throughout the vegetation period. The first treatment is made immediately after buds swell in early spring, and the second spraying is carried out when 4-5 leaf plates open on the stems. The third treatment is carried out at the end of flowering, and this time it is recommended to use a product that fights both black spot and peronosporosis and powdery mildew. If the bushes are very badly affected by black spot, after the pruning is completed or the leaf fall is over, they are liberally sprayed with a solution of a product containing copper.
After the procedure, the plant should literally be washed with the solution of the drug. Those sleeves on which there are symptoms of desiccation should be pruned. Very effective in the fight against black spot on grapes are fungicidal preparations such as: Captan, Triadimenol, Maxim, or Mancoceb.
To prevent the vineyard from being affected by this fungal disease, the following preventive measures are used:
- plant only absolutely healthy planting material;
- examine the plants systematically for symptoms of the disease;
- as soon as the first symptoms of the disease are found, cut out and destroy by fire all affected parts of the bush;
- stems should not lie on the soil, so they must be tied up;
- feed the bushes properly with a balanced fertilizer, which should necessarily include boron and zinc.
It is very difficult to completely cure black fungal spot, so the fight against it can take a long time.
But even if you manage to cure grapes of this disease, do not stop regular preventive spraying.
Black spot disease (escariosis) appears in early June
Black spot disease on flowers
Black spot disease on roses
The causative agent of black spot disease on roses is the fungus Marssonina rosae, It is capable of attacking both the green stems of the bush and its foliage. On the front surface of the leaf plates, whitish-red spots appear, which eventually turn black, they are rounded and radiant, as if fringed. The lower foliage is initially affected, but the infection quickly spreads throughout the bush. Affected leaf plates turn a brownish-gray color, and later twisting, dying, and flying off can be observed.
The plant becomes weaker and produces few or no buds. If the plant is very heavily infested, it may drop off all of its leaves by the time autumn arrives.
Cut off all diseased leaves immediately after the first symptoms of the disease are noticed and remove any fallen leaves from under the shrub. Spray regularly every 7-12 days with a solution of a fungicide such as Abiga-Pika, Bordeaux liquid, Previcur, Skor, Topaz, Fundazole, Mancozeb, Thiophanat methyl or Trifloxystrobin. Soil near the rose is sprinkled twice or three times with a solution of Phytosporin-M.
In autumn, when preparing the bush for wintering, remove all foliage from it, and collect and fallen leaves, all this is destroyed by fire. Then the bare bush is sprayed with a solution of iron sulfate (3%). In spring, before the growing season begins, cut all branches and stems back to healthy wood and then spray the plant and the soil surface around it with one of the remedies listed above.
The symptoms of black spot, or Marsonina, on the rose are very similar to those of the following diseases: brown spot, peronosporosis, phyllostictosis, cercosporosis, septoriosis, purple spot, ascochytosis and sphacelloma. But you don't have to worry that you might misdiagnose a diseased rose because fungicidal drugs are used to treat all of these diseases.
How I Cured Roses from Black Spot, Rust, Gray Rot and Mildew!
Black Spot Treatments (Fungicides)
Before deciding what treatment for black spot it is advisable to research the action and the purpose of the particular product. The fungicides most commonly used against black spot and other fungal diseases are described below.
- Abiga-Pic. A broad-spectrum contact preparation containing copper. It is used in the control of bacterial and fungal diseases.
- Baktofit. A biological agent effective in controlling both fungal and bacterial diseases.
- Bordeaux liquid. This broad-spectrum contact agent is used for prevention of fungal diseases and for treatment of fruit, melon, vegetable, berry and other crops.
This biological bactericide is used to suppress certain bacterial and fungal diseases in the soil and on crops.
- Captan. This contact agent is characterized by its multidirectional mechanism of action on fungal organisms.
- Maxim. This contact agent is used for seed dressing.
- Mancoceb. The contact agent is used for prevention of fungal diseases.
- Nitrafen. A complex action agent characterized by bactericidal, insecticidal and fungicidal properties.
This broad-spectrum systemic contact agent is used to treat fungal diseases.
- Planriz. This microbial agent protects crops against a range of diseases, and is distinguished by its fungicidal-insecticidal and bactericidal properties.
- Previcur. A systemic drug characterized by its protective action, it also stimulates growth.
- Scor. Such a systemic drug is characterized by its prolonged protective action against fungal diseases, and it is also effective in treating them.
- Tyophanate-methyl. This systemic contact agent combines the properties of a fungicide, pesticide and insecticide. It is used for preventive treatments.
- Topaz. This systemic agent is used to control the whole complex of fungal diseases.
- Triadimenol. This systemic drug is used to treat crops during the growing season and is effective against a large number of diseases.
This effective systemic-contact preparation is characterized by its preventive and curative effects, and it is used against a variety of plant diseases.
- Phytolavin. This biological bactericide of systemic action is used to protect and treat plants against a variety of bacterial and fungal diseases.
- Fitosporin-M. It is a biological contact fungicide.
Such a microbiological agent is used for the prevention of a large number of bacterial and fungal diseases.
- Fundazole. Such a systemic fungicide and broad-spectrum protectant is effective in controlling a variety of fungal diseases.
- Hom. A contact and systemic-local agent used to treat a variety of plant diseases.
- Euparen. A prophylactic contact drug that promotes the destruction of condylar sporulation.
- Euparen. Such a systemic remedy is used for preventive treatments of fruit and vegetable crops against many diseases.
There are several folk remedies that are used more for prevention of this disease than for treatment of plants affected by black spot.
- 2 tbsp. water is combined with 1 milligram of iodine. The resulting mixture is sprayed on the plants.
- Water is combined with cowpea in a ratio of 10:1, the mixture is allowed to infuse for several days. Then at the beginning of spring it is poured on the rose after the cover is removed.
From May to July it will require 2 or 3 more such applications.
- Boil 30 to 40 grams of garlic or onion husks in water and allow the broth to infuse for 6-8 hours. Use the strained mixture to spray the rose bushes and the soil near them. If there are flowers on the bush, pour the decoction under the root, otherwise petals may change their color after spraying.
According to many gardeners and horticulturists citrus decoction and herbal infusions (nettles, horsetail, etc.
) are of low efficiency. ) are ineffective against black spot.
Diseases of Roses, Spots Appear on Leaves - What to Do and How to Treat Roses.