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Alternaria is a fairly common disease that affects various plants at different stages of development. This ailment is caused by imperfect fungi of the genus Alternaria.
Another name for Alternaria is dry or black spot. It can be found everywhere, but the damage from this very dangerous disease is most noticeable in the southern regions.
You will learn how to recognize this disease in different cultures in our article. We also recommend watching a useful video on the topic.
What it is?
Black spot of rapeseed is also caused by fungi of the genus Alternaria... In this culture, the lower part of the plant is affected first, and then the disease spreads upward. Black spot can develop on:
Where and how is it manifested?
The disease makes itself felt during the budding stage and continues throughout the summer period. Alternaria manifests itself on parts of the plant in the form of brown and necrotic spots, on which dead tissue is visible. On the damaged areas, brown spots with a dark coating are formed, which consists of fungal spores.
These spots, under favorable conditions, become noticeable 2-3 days after the lesion. After 2 days, gray spores with transverse and longitudinal septa appear on them. Damaged parts become brittle and brittle.
Alternaria develops when dry hot weather alternates with night dews or rains. The best temperature for the development of this disease is + 24 ° С-30 ° С, the minimum is + 7 ° С.
Why is it dangerous?
The danger of Alternaria lies in the transfer of spores to healthy plants... This is done by:
IMPORTANT: Spores can persist for a long time in the remaining plants and ground, further causing primary infection. The disease results in a 50% loss in yield.
Which culture is striking?
This disease mainly affects the following cultures:
- tomatoes and cabbage;
- potatoes and pumpkin;
- pepper and sunflower;
- eggplant and zucchini;
- grapes and cereals;
- carrots and onions;
- henbane and belladonna;
- dope and tobacco;
- hybrid petunia, etc.
- family of nightshades.
How to find?
Alternaria can be detected by the following signs. Places appear on the surface of the plant that differ sharply from the healthy part. They are irregularly shaped, dented dark spots. Often wrinkles form on their surface. Rotting with Alternaria occurs as dry rot.
General principles of protection and struggle
There are common measures for all plants to protect and control this serious disease. These include:
- compliance with crop rotation;
- weed control;
- careful incorporation of plant residues;
- using exclusively healthy and sustainable seed material;
- seed dressing;
- fungicidal treatment.
Fungicide treatment must be done before the plants show symptoms of Alternaria.
Features of diagnosis and treatment in individual cases
Early and late dry spotting occurs... With early spotting, 15-20 days before flowering begins, clear spots with a bloom are formed, which, if severely affected, merge, the leaves turn yellow. Later they dry up. If the disease touches the stems strongly, then ulcers can be found on them. As a result, the plant will wither over time.
ATTENTION: Late dry spot mainly occurs on leaf tips at the end of flowering. The spots are dark brown in color, on their surface you can see a velvety olive bloom. In dry weather, the disease can be detected by the leaves twisted upward in lobules, which look like boats.
In tomatoes, this disease is called zonal or dry spotting.... It poses a danger to the plant, manifests itself immediately after the tomato seedlings are planted in a greenhouse or open soil.
This disease is much easier to prevent, to insure against possible loss of crops. It is necessary to well remove the remnants of vegetation and adhere to the rules of crop rotation. According to them, tomatoes should not be planted in the place where they were previously planted:
There should be spatial isolation between tomatoes and potatoes.
Alternaria on a root crop mainly appears in mid-June and lasts until autumn... The disease prefers medium late varieties. After the defeat of the stems and leaves, the growth of tubers slows down, which are also covered with dark spots, or even stop forming altogether.
The development of Alternaria is favored by:
- lack of nitrogen;
- drip moisture that lasted more than 2 hours in a row;
- the presence of pests on the crop.
Before planting tubers, it is recommended to process them with such preparations:
- Ridomil Gold;
The first treatment must be done no later than the weather conditions favorable for the development of the disease.... The following manipulations are carried out with a break of 10-14 days.
Alternaria on wheat crops begins to manifest itself during flowering and when the grain is filled with milky ripeness. This can be seen from the dark spots appearing on the scales of the spikelets. Subsequently, during the period when the grain ripens, the blackening of the embryo is noted. Flour from such an embryo is dark in color and has low baking qualities. Plants grown from these seeds do not grow and develop well, which leads to a decrease in yield. The methods of struggle are the same as in cases with other cultures.
The first signs of grape disease appear in May.... Light silvery spots appear on the leaves and shoots. The peel of the berries begins to shine, then a dark fungal bloom forms on it. They become shriveled, stop ripening, die off, and those that do ripen acquire an unpleasant taste.
For the treatment of grape alternariosis, drugs are used:
- Ridomil Gold;
The disease is recorded during the period of seed filling, most often 20-25 days after flowering ends. A brown oval spot appears on the back of the basket and the expanded axis of the inflorescence, which spreads further. There is a gradual damage to the inner tissues of the basket and the entire plant.
As a result, nutrients cease to be supplied to the seeds, the basket becomes brown. Baskets and seeds are getting puny often, infection leads to the fact that the stems break and the plant dies.
In order to prevent the development of sunflower alternaria, it is necessary to observe general protection measures, increase soil fertility, and harvest the crop at the earliest optimum date. Do not forget to use chemical control methods.
The disease is easily seen by the watery white spots on the feathers.... On their edges, reddish spots often appear; when they are combined with white ones, the onion dies off very quickly. It is recommended to treat onions with fungicides when there are already signs of the disease on it, and moisture remains on the feathers for 11 hours.
At first, the disease on zucchini manifests itself in the form of small spots of white and brown color, then the surface of the vegetables is covered with a velvety black bloom. They gradually increase in size, then cover the entire leaf, which withers and dies off.
A diseased plant develops and grows poorly. To prevent this from happening, you need to take appropriate measures.
It is necessary to destroy weeds, remove the collected tops away. In the presence of Alternaria, bushes with zucchini must be sprayed with fungicidal preparations.
- In order to prevent the occurrence of Alternaria, the best solution would be to spray the plants with appropriate solutions.
- It is imperative to disinfect the soil, in a timely manner to destroy already diseased plants.
- It is necessary to choose varieties that are resistant to this disease.
- Tall plants need to be tied up, it is recommended to remove the lower leaves.
- Mechanical damage to tubers must not be allowed.
- Affected potatoes must be discarded during the process.
Fertilizers need to be applied correctly... It is necessary that the concentration of nitrogen in the soil is not exceeded. It is imperative to introduce such mineral fertilizers into it, which contain potassium.
If alternariosis can be detected at the initial stage, then it will be possible to cope with it in one season. However, it cannot be argued that the disease will not appear again, therefore, it is imperative to carry out preventive and agronomic care measures. If all the rules are followed, then the plants are not threatened with any diseases.