How to defeat late blight in a greenhouse?
Phytophthora, which has crossed the threshold of harmfulness, is a real scourge of gardeners. Especially dangerous is the disease in the limited space of greenhouses and hotbeds. In 2-3 days, under optimal conditions for the spread of the disease, up to 70% of the tomato crop dies. Blight spreads by zoospores that winter on the remains of leaves, stems of various plants, in soil, on mounts and other construction and utility parts of greenhouses and near the greenhouse space. They retain their viability for 3 to 5 years and are able to survive in the soil 20-30 degrees of frost. Therefore, a thorough annual disinfection of the greenhouse is urgently needed, which will eliminate phytophthora spores and prevent the onset of the disease in the new season.
- Preparing the greenhouse after late blight for the next season
- Methods for disinfecting a greenhouse from phytophthora
- Disinfection of greenhouse soil from late blight
- Ways of re-infection of the greenhouse with late blight
- Conditions for breeding zoospores phytophthora in a greenhouse
Preparing the greenhouse after late blight for the next season
In the fight against late blight, there is no separate pesticide that would spray the greenhouse - and late blight is destroyed. The effectiveness of the fight is determined by a set of autumn-spring work and constant diagnostics to identify the disease in cultivated plants, the timely implementation of protective measures.
The preparation of the greenhouse for the next season can be divided into 2 stages:
- external cleaning and disinfection of the territory and frame of the greenhouse itself;
- internal work on the disinfection of the frame, premises and soil.
Greenhouse preparation from the outside
After harvesting, the space around the greenhouse is freed from broken containers and tools. All working tools used during the season (shovels, secateurs, files, knives, etc.) are repaired, disinfected, and transferred to a specially designated dry room.
They collect and destroy leaves that have fallen around the greenhouse, dry weed residues and other debris in which zoospores of phytophthora, other diseases and pests can winter.
The top cover of the greenhouse is thoroughly washed from dust. It is possible with soap and water, but preferably with the use of disinfectants. To disinfect the greenhouse from late blight, use a solution of bleach or copper sulfate.
Attention! When working with disinfectants and other chemicals, be sure to use personal hygiene measures.
If the greenhouse is covered with a coating that is removable for the winter, after washing it is carefully removed, folded and stored in a dry, sanitized room. Inspect the frame of the greenhouse, carry out the necessary repairs.
If the greenhouse is covered with polycarbonate or glazed, then repair work is carried out to replace the glass or repair damaged parts of the polycarbonate. The slots in the transoms are sealed with sealant. Then, the outside of the greenhouse coating and the frame itself are thoroughly washed. Snow is constantly removed from the greenhouse during the winter.
To reduce the infestation of the territorial space near the greenhouse, nightshade, especially potatoes (the crop most affected by late blight) are never planted near the greenhouse.
Instructions for conducting internal work in the greenhouse
In order to properly prepare and disinfect phytophthora from the interior of the greenhouse, it is more practical to carry out all the work in the following order:
The entire portable open irrigation system (hoses, watering barrels, containers, tools, etc.) is removed. Wash, disinfect and transfer them to the utility room.
They clean the premises of the greenhouse from shelves, boards, racks, pegs, twine residues. Sort, must be disinfected, dried and stored indoors.
They clean the beds from plant debris - potential sources of late blight. Remove the tops and roots, uncleaned, diseased, unripe fruits and other plant debris. Healthy tops (for example, cucumbers) can be laid in compost heaps. All vegetation and garbage removed from the greenhouse, especially if the crops were affected by late blight, must be burned.
Before disinfection, the greenhouse is “bathed”, saving the room from dust and dirt. Wash the inner surface, including the frame, with soapy water or with the addition of copper sulfate. Galvanized metal structures are washed with 9% vinegar solution.
After performing general work, disinfectant solutions from late blight and the necessary equipment are prepared.
The prepared solution of freshly slaked lime from the back wall of the greenhouse to the doors is whitened, literally, smeared with a thick suspension of all the wooden structures of the greenhouse, without missing hard-to-reach places, cracks, ceilings, fastenings, supporting posts, etc. The metal frame or individual metal parts in the greenhouse must be painted. If it is not possible to paint, then they are treated with Bordeaux liquid.
If in the autumn they didn’t have time to disinfect the greenhouse from late blight, then in the spring 3-4 weeks before the start of seasonal work, the greenhouse is washed, wooden floors and the rest of the frame are whitewashed with lime, metal frames are treated with 9% vinegar. The room is kept closed for 2 to 5 days, ventilated and treated with biofungicides (see the section "Use of Biological Preparations" below).
Remember! When working with chemical solutions, be sure to follow the rules of personal hygiene: a respirator, glasses, a hat, gloves, shoes, and outer clothing.
Methods for disinfecting a greenhouse from phytophthora
Greenhouse disinfection methods can be divided into:
The most accessible disinfection of the room with solutions:
- slaked lime;
- concentrated solution of copper sulfate;
- sulfur drafts;
- chemical fungicides.
For cooking bleach 0.5-1.0 kg of dry matter is dissolved in 10 l of water. They insist 3-4 hours, filter and spray the entire interior, thoroughly coat all wooden structures (additional protection against decay). Sealed for 2-3 days, then ventilated. After aeration from bleach lime vapors, the wooden frame is treated with a 5-10% solution of copper sulfate, and the metal frame is painted (at least after 2-3 years).
You can disinfect the room with a solution slaked lime. The following ingredients are used to prepare slaked lime solution: 3-4 kg of freshly slaked lime are mixed with 0.5 kg of copper sulfate and 10 l of water. The wooden frame, brickwork and all the places where pathogenic microflora can overwinter harmlessly for themselves are carefully whitened in thick suspension.
Blue vitriol perfectly copes with late blight. A saturated solution is prepared from 100-150 g of vitriol per 10 l of water and with this composition all places of accumulation of pathogenic microflora are carefully whitened.
Of the various disinfection methods, the most popular is lump sulfur fumigation. The method takes significantly less time and labor. Smoke penetrates all inaccessible places in the room, leaving no late blight chances for survival. Lumps of sulfur 100-150 g are laid out on iron trays. Trays with sulfur mixed with kerosene, have one per 1.0-1.5 square meters. m of the greenhouse area and set on fire, moving from the back wall to the exit from the room.
The room treated from late blight is hermetically sealed and left for 4-5 days, then ventilated. Work must be done with a respirator, goggles and protective clothing. It is important to remember that sulphurous anhydride formed during the burning of sulfur is dangerous to human and animal health.
Sulfur Fumigation can be done with ready-made checkers “Fas”, “Climate”, “Volcano”. The method of use is detailed on the packaging.
Remember! If the frame of the greenhouse is metallic and not painted, sulfur fumigation cannot be used due to the activation of corrosion processes.
The chemicals market offers a number of versatile, effective chemical fungicidesthat quickly disinfect phytophthora room and soil in the greenhouse. They include compounds of sulfur, iron, mercury, copper, manganese and others, which pose a great danger to the life and health of humans and animals.
Therefore, in private estates it is better not to use them or use them with great care, clearly following all the recommendations for working with such substances. Conditions for working with fungicides and other requirements are always written on the package or as a recommendation application.
Chemical fungicides from late blight can be used in the form of fumigation or spraying, which is recommended to be carried out in the morning or in the evening at a room temperature in the range + 10 ... + 25 ° С.
Of the chemical fungicides from late blight, it can be recommended for disinfection of the room by spraying:
- "Ecocide-S", 5% solution;
- Virkon-S, 2-3% solution;
- Virocid, 1% solution.
- "Oksikhom", 2-3% solution;
- "Abiga-peak", 3-5% solution.
Working solutions spray the premises, leave them closed for 2-3 days, then ventilate and dry.
Chloropicrin is used to aerate the premises, spending 15-40 g of substance per cubic meter. Processing is carried out at a temperature not lower than + 12 ° C. The room is kept closed for 3-5 days, then aired.
The use of chemicals from late blight can be replaced solar "roasting" of the room. If autumn is hot and dry, close the room. The temperature inside rises to + 35 ° C. The room is kept hermetically sealed from several hours to 2–3 days. Zoospores at a temperature of + 30 ° C decrease their activity, and at + 35 ° C they begin to die. Naturally, the source of the disease does not die completely, but the room is cleared of pathogens by 70-80%.
In cold regions, it is actively used to combat late blight and other diseases. Greenhouse “freezing”. It is effective for small greenhouses. In the winter cold, the greenhouse is left open for several days. It is not necessary to cover the soil with snow, since phytophthora overwinter comfortably under its zoospore layer. After freezing, the soil in the greenhouse is covered with snow.
The use of biological products
At home, especially if the greenhouses are small, it is better to use biological preparations to disinfect the greenhouse from late blight. The drugs are developed on the basis of positive microflora that is harmless to humans, which has the ability to suppress fungal diseases for several years. The only condition: biofungicides do not work at low temperatures. Room treatment with solutions of biofungicides should be carried out at a room temperature of at least + 12 ... + 14 ° C.
For disinfection of the premises use biological product "Fitop-Flora-S". 100 g of the substance are dissolved in 10 l of dechlorinated water and the room is thoroughly sprayed. After 1.5-2.0 weeks, the spraying is repeated.
Biofungicide "Fitosporin" attributed to universal disinfectants for the greenhouse. It is used for processing rooms, soil and plants during the growing season. For spraying the premises, a saturated working solution is prepared (50 ml per 10 liters of water) and the room is carefully treated. After spraying, the greenhouse is kept closed for 4-5 days. Then carry out further work.
In the same way they process the greenhouse Trichodermin, Bactofit and other biological products.
Integrated greenhouse processing
In recent years, greenhouses have been using a set of measures to combat late blight: “roasting”, “freezing” the premises, along with processing plants in season with biological products “Fitosporin-M”, “Alirin-B”, “Krezatsin”, “Trichoplant”, “Bactofit "," Planzir "and others. These same drugs are effective in the disinfection of premises and soil. Detailed dosages and conditions for the use of biofungicides are described in detail on the packaging, in the insert or in the accompanying recommendations.
For home greenhouses, the most acceptable in terms of labor, cost and safety for health is the integrated use of temperature and biological methods of processing the room, it provides effective protection against late blight and allows you to harvest organic vegetables.
Disinfection of greenhouse soil from late blight
In a confined space, greenhouse soil quickly loses its agronomic structure, reduces fertility, increases acidity, and accumulates pathogenic flora and fauna. To increase the duration of use of the greenhouse, greenhouse soil must be systematically healed. Soil improvement is carried out in several ways.
The most harmless to the environment, humans and animals - full or partial replacement of soil in the greenhouse. The method is very simple, but time-consuming and more suitable for small greenhouses. Usually, once every 2-3 years (it is possible and annually), the top 10-25 cm layer of soil is carefully removed and taken out to a prepared place, where a “layer cake” is formed from the worked land, dry healthy tops, autumn leaves, compost.
Each layer with a height of 5-15 cm is shed during the warm period with water or with a solution of Baikal EM-1, Ekomik, Trichoplant, Azotofit and others. Composting using solutions of these biological products contributes to the destruction of negative microflora and faster processing plant material.
Constant shoveling speeds up the process and after 2 years the updated soil can be used for garden crops. As a rule, the top layer is replenished with forest or field land or soil, which was never used for vegetable and other garden plants, was not treated with chemical preparations. The renewed topsoil is broken up into beds and sown with winter green manure, which will enrich the soil with organic matter and at the same time destroy part of the painful microflora (see the article “What green manure to sow in autumn”).
Improving the topsoil in the greenhouse can be done in another way. Old soil in a layer of 15-20 cm can literally be sorted out or sifted through sieves with wide openings (0.3-0.5 cm). The soil will be cleaned of excess roots, rotting residues, and some pests. The cleared soil is seeded with green manure.
With strong soil infection with late blight, a high cleaning effect is achieved by sowing white mustard for one season. First, soil is treated with lime, and then white mustard is sown. The combination of these two methods almost completely cleans the soil of the pathogen phytophthora (see the article "What green manure to sow in spring").
In dachas and personal garden plots it is better to use biological soil disinfection method. It is especially effective in combination with pre-heat tillage.
After processing the greenhouse with bleach, slaked lime, copper sulphate, part of the solution enters the soil. Mix the top layer by loosening. We provide the dried soil to the sun. High temperature in the soil dried and warmed by the sun (+ 30 ... + 35 ° С) will destroy a significant part of the pathogenic microflora and improve the soil.
If in the fall they did not have time to perform work on disinfecting the soil from late blight, then they are performed 2-4 weeks before the start of seasonal work in the spring. The soil is poured with hot water, covered with a film for deeper steaming.
Both methods of hot soil disinfection destroy not only part of the pathogenic, but also beneficial microflora. After such disinfection, the soil needs resuscitation.To restore beneficial microflora, if necessary, moisten the soil, bring it to a temperature of + 12 ... + 14 ° C and treat it with a solution of Baikal EM-1, Ekomik, Radiance or scatter Emochka-Bokashi, covering it with a rake and covering it with cover material .
In a warm, humid environment, effective microorganisms (EM) begin to multiply intensively, using pathogenic microflora as food. To maintain a healthy soil level during seasonal work, approximately 1 time every 2-4 weeks, the same biofungicides are applied to the soil with watering as for the treatment of plants - “Gamair”, “Alirin-B”, “Trichoplant”, “Haupsin”, "Fitosporin-M" and others. How to prepare solutions of biofungicides for tillage is indicated in the accompanying recommendations or on the packaging of the drug.
At home, even hasty people who like to do everything quickly are not recommended to disinfect greenhouse soil with chemicals.
Of chemical methods of tillage from late blight in private greenhouses, it is permissible to treat the soil with a hot solution of potassium permanganate (dark pink) or a solution of copper sulfate, prepared at the rate of 25-30 g of the drug per 10 liters of water. 2-3 days after soil treatment, digging is carried out on an incomplete bayonet of a shovel and green manure is sown. Often and in high concentrations, using these methods of disinfecting the soil is not recommended. Manganese and copper, which are part of salts, accumulate in the soil and inhibit plants.
Ways of re-infection of the greenhouse with late blight
Despite the disinfection of the greenhouse, late blight can occur in the new season on tomatoes and other nightshade. Ways of re-infection:
- poor-quality and not disinfected seed material;
- diseased seedlings;
- drift of zoospores by late blight from open areas, neighboring gardens through open transoms during ventilation;
- the infection can get into the soil with a drop during high humidity in the greenhouse, especially if the latter was not well disinfected;
- non-disinfected tools and auxiliary devices (hoses, containers, shovels, etc.) can become a source of infection.
How to find out that late blight appeared in the greenhouse?
Phytophthora infection is most pronounced on tomatoes, the most common crop grown in protected ground.
The lower part of the leaves, located close to the soil, is covered with separate whitish spots of arachnoid plaque. They merge, acquire a brownish tint. Leaves curl, dry, fall off. Sometimes the disease begins with damage to the edges of the upper leaf blade with brownish spots.
After 2-3 days, the stems and petioles become covered with brown spots. This sign indicates the entry of late blight into the most active phase of reproduction. During this period, lightning damage to the entire tops, inflorescences and fruits is observed.
Fruits are initially covered with dark spots located under the skin of the fruit. Their color under the skin is brownish red. The spots quickly soften, tomato rot begins, caused by concomitant rot.
You can save the crop from late blight only by urgent harvesting and laying for ripening. How to properly lay the fruits for ripening is described in the article "How to properly ripen and store tomatoes."
Remember! Do not use tomatoes for food, even slightly damaged by late blight (that is, at the stage of dark spots).
If you do not take timely plant protection measures, then the epiphytotic reproduction of late blight will destroy the crop in a matter of days.
Conditions for breeding zoospores phytophthora in a greenhouse
Favorable conditions for the start of activation and reproduction of phytophthora zoospores in the greenhouse and other enclosed spaces are:
- high unregulated humidity;
- drops from the greenhouse coating;
- differences in night and day temperatures.
If the air humidity in the greenhouse is higher than 75%, and the air temperature is + 12 ... + 15 ° С, then zoospores begin to multiply actively. Together with a drop, they fall into the soil. The incubation period lasts 7-12 days and an outbreak of the disease occurs. Phytophthora cannot be destroyed forever. She is constantly returning.
Therefore, to obtain a full-fledged healthy crop, along with the systematic disinfection of the greenhouse, it is necessary to carry out protective measures during the growing season of vegetables to preserve tomato fruits from late blight.
Read more about the protection of tomatoes from late blight in the articles “Late blight of tomatoes. Prevention and control measures "," Why tomatoes rot on a branch. "