Content
Alternaria tomato blight is a common disease that affects plants mainly in greenhouses. However, specimens planted in open ground are not immune from it. The disease greatly weakens the bushes themselves and causes a significant reduction in yield. Alternaria tomato blight develops quickly, so even with proper treatment, “losses” are inevitable. Accordingly, it is necessary to reduce the risk of tomatoes being damaged by fungus - preventive measures will help with this.
Description and photo of Alternaria
Alternaria blight is a fungal disease that affects not only tomatoes and other plants from the Solanaceae family, but also fruit trees, berry bushes, legumes, grains, and sunflowers. The developing pathogen gradually deprives the plant of its strength - without treatment, it loses its tone and withers due to “failures” in the process of photosynthesis and metabolism.
Alternaria has been given several “alternative” names:
- macrosporiosis;
- dry spotting;
- zonal spotting;
- brown spotting.
At an early stage of development, Alternaria blight on tomatoes appears as grayish-brown, dry, round spots on the leaves. Initially, their diameter is small, but they quickly “blur” and the surrounding tissues turn yellow.
The pathogen spreads from bottom to top, starting from leaf blades located closest to the ground
If the bushes are not properly treated, the fungus will also attack the fruits. At first they become covered with individual “pressed-in” brown spots, then they darken completely.
In adult bushes, along with tomatoes, the stems also suffer from Alternaria. Without treatment, they become covered with longitudinal cracks, become brittle, and break easily.
Alternaria blight on tomatoes can occur during the entire period of active growing season - from the moment of growing seedlings to harvesting. In young seedlings at home, an additional symptom is observed - black “rings” at the base of the stems. In open ground, the pathogen is activated at a temperature of 7-10 °C.
Causes
Healthy plants most often “catch” the pathogen from the soil, from plant debris remaining in the garden from the previous season, or from weeds that are suitable for it as “intermediate” hosts. Sometimes tomatoes have to be treated for Alternaria blight due to the fault of the gardener. The pathogen is easily transferred from diseased bushes to healthy ones if disinfection of equipment is neglected.
Alternaria tomato spores are spread by wind and raindrops
The experience of gardeners shows that in the presence of “risk factors”, tomato bushes require treatment for Alternaria blight more often:
- alternation of fairly warm weather and heat with constantly high humidity;
- large differences between day and night temperatures, contributing to heavy dew;
- non-compliance with crop rotation rules;
- planting tomatoes next to other Solanaceae or plants that are also susceptible to Alternaria;
- regular “interruptions” with watering;
- presence of sunburn, any mechanical damage;
- lower leaves touching the ground.
Danger of disease
Alternaria tomato blight means inevitable yield losses. The affected bushes develop slowly, very few buds appear on them, flowers and fruit ovaries fall off. Existing tomatoes become smaller, deformed, and their flesh is hard and almost tasteless.
Without timely treatment, the resulting reduction in yield averages 30-50%
Measures to combat macrosporiosis of tomatoes
The use of folk remedies for the treatment of tomato Alternaria is most often a waste of time. Gardeners use them, like agricultural techniques, in conjunction with other preventive measures.Agrochemicals or biological products with fungicidal properties will help get rid of the disease.
Agrotechnical techniques
Agrotechnical measures are aimed at creating conditions that reduce the likelihood of tomatoes becoming infected with Alternaria to a minimum, so that they do not have to resort to treatment:
- timely removal of lower leaves, both infected and healthy;
- proper watering;
- regular ventilation of the greenhouse or greenhouse;
- choosing a place for planting in open ground so as to ensure normal air circulation.
In tomatoes, you can gradually “expose” the stem by half - this will not harm the bushes
Folk remedies
As “auxiliary” measures in the treatment of tomato Alternaria blight, it is recommended to spray the bushes with compounds with antibacterial properties at intervals of 15-20 days. For 10 liters of water take:
- kefir or whey (1 l) and iodine (20 drops);
- baking soda or soda ash (30 g);
- sifted wood ash (0.5 kg);
- potassium permanganate (about 0.5 tsp, until bright pink).
Potassium permanganate is suitable for disinfecting seeds, soil, and treating adult plants
Chemicals
Agrochemicals with fungicidal properties are the only means suitable for treating tomatoes from Alternaria in severe cases. However, they must be used in strict accordance with the instructions, otherwise the tomatoes will become unsuitable for food.
It is recommended to use chemicals against Alternaria tomato blight before flowering and the formation of fruit ovaries, so that their active ingredients have time to “exit” from the plant tissues.If the bushes require treatment at a later date, only contact-type drugs are used.
Suitable fungicides include:
- Quadris SK;
- Acrobat MC;
- Ordan;
- Ridomil-Gold MC;
- Polyram DF;
- Maksim;
- Abiga Peak.
Usually, at the early stage of Alternaria blight development, 1-2 treatments of tomatoes with fungicides are enough. In “severe cases” their number is increased to 3-4 times.
Both the plants themselves and the soil need to be sprayed with an agrochemical solution.
Biological products
Preparations of biological origin help in the treatment of tomato Alternaria due to the presence of strains of bacteria or fungi that are “hostile” to the pathogen and “feed” on it. However, it must be taken into account that biological products begin to “work” more slowly than agrochemicals. In severe cases, they most likely will not give the desired effect, since they act more mildly.
Biological products for the treatment of tomatoes are used by shedding the soil and spraying the plants. Once in the soil, they additionally activate the work of the “local” microflora. As a result, the soil fertility increases and it becomes looser.
To treat Alternaria blight on tomatoes, use:
- Fitolavin;
- Alirin-B;
- Gamair;
- Trichodermin;
- Fitosporin-M;
- Phytocide.
Biological products can be used at any stage of the active growing season
Features of fighting in a greenhouse
Tomatoes in a greenhouse need treatment for Alternaria blight much more often than in open ground - a microclimate favorable for the fungus is created there. In a “closed space”, spores spread much faster, which means more damage to plantings.
Accordingly, when growing tomatoes in a greenhouse, the room must be regularly ventilated, reducing the level of air humidity. With good aeration, the causative agent of Alternaria feels much worse than in a “stagnant” atmosphere.
“Stale” air is preferred not only by the fungus that causes Alternaria blight, but also by many other pathogens and pests
Along with this, “preventive” treatment of tomatoes is recommended to protect against the disease. To prevent the development of Alternaria, from the moment the seedlings are planted and before flowering, the bushes are sprayed with any fungicides at least once a month. Then, before the formation of fruit ovaries, a “break” is taken, and after that the treatments continue, using only biological products.
Preventive measures
In order not to have to “accelerately” look for ways to treat tomatoes from Alternaria blight, it is strongly recommended to study preventive measures in advance and not neglect them. Knowing and practicing “basic” gardening principles will also help.
Prevention includes:
- Placing beds with different crops from the Solanaceae family as far away from each other as possible. Alternaria blight can “spread” from tomatoes to other plantings, and vice versa. The number of plants in need of treatment is increasing very quickly.
- Compliance with crop rotation rules. The most unsuccessful predecessors for tomatoes are any Solanaceae. Especially if last season the crops in this bed required treatment for Alternaria blight.
- Treating seeds before planting in a solution of any fungicide. Or soaking in hydrogen peroxide diluted with water, potassium permanganate. Disinfection is especially important if the seeds are collected independently.
- Planting seedlings according to the scheme recommended for a given variety or hybrid. The reason is the same - to prevent the rapid spread of Alternaria between tomato bushes and gain time for treatment.
- Timely watering. Any method is suitable, with the exception of sprinkling.
- Timely ventilation of the greenhouse or greenhouse. In this case, it is necessary to exclude cold drafts that weaken the plants. With reduced immunity, tomatoes require treatment for Alternaria blight much more often.
- Regular spraying with “supporting” drugs - biostimulants, adaptogens, immunomodulators. They are carried out regardless of whether the tomatoes “survived” treatment for Alternaria blight or whether the bushes have characteristic symptoms.
- Cleaning up plant debris and digging up the soil at the end of each season. It is especially important to clean the bed if the crops on it were affected by Alternaria this season and required treatment. In a greenhouse, it is generally advisable to completely change the top layer of soil or at least disinfect it.
The planting pattern for each variety or hybrid is determined by the dimensions of the plant
Resistant tomato varieties
There are no varieties and hybrids of tomatoes for which breeders guarantee absolute protection against Alternaria blight. However, the experience of gardeners shows that varieties that are resistant to cracking are less susceptible to infection:
- Golden Bullet;
- Aurora;
- De Barao;
- Firebird;
- Debut;
- Hope;
- Pickling miracle;
- Tanya;
- Diva;
- Linda;
- Steak;
- Sanka;
- Ray.
Conclusion
Alternaria tomato blight is a disease that inevitably negatively affects the yield volume and quality of the fruit. Bushes in a greenhouse are affected by the fungus much more often, so when growing indoors it is necessary to pay increased attention to prevention. The disease develops quite quickly, however, the use of modern agrochemicals and biological products can minimize the damage. Folk remedies for the treatment of Alternaria are ineffective; in most cases, their use is a waste of time.
Reviews about the treatment of tomato Alternaria
