5 effective ways to treat powdery mildew on tomatoes. Disease prevention

Home / Pests and diseases

Back

Published: 06/09/2019

0

5/5 — (1 vote)

Ash or powdery mildew on tomatoes is an insidious disease caused by harmful fungi. The pathogen affects plants and without prompt treatment measures it is easy to lose most of the tomato harvest. The infection is especially dangerous for greenhouse tomatoes, since shelters most often have a microclimate favorable to the pathogen.

• 1 Why is powdery mildew dangerous and where does the infection come from?
• 2 How to recognize the disease?
• 3 How to deal with powdery mildew 3.1 Folk remedies
• 3.2 Biologicals
• 3.3 Chemicals

What it is?

Powdery mildew, or as it is also called, white or ash, is a dangerous disease caused by microscopic parasitic fungi.

They live in the soil and belong to the fungal order Erisifaceae (Powdery mildew).

The disease can affect crops growing in different conditions:

• Houses;
• open ground;
• greenhouse

When affected by this disease, the foliage of the plant becomes covered with a white coating of mycelium, on which spores ripen and droplets of liquid form. Because of this, the disease got its name.

Powdery mildew takes away nutrients from the shoots, and this is its main danger.

Bacterial diseases of tomatoes

Black bacterial spot. Small black round spots on leaves and unripe fruits (ripe ones are not afraid of it), elongated spots on stems and cuttings - this is a signal to take action, because the plants are affected by black bacterial spotting. Most often, the disease attacks plants in open ground in warm, rainy weather.

Control measures: first of all, you need to take care of healthy seed material.

Before sowing, the seeds should be soaked in a 1% solution of potassium permanganate (10 g per 1 liter of water) for half an hour, then they are thoroughly washed with water. Diseased plants are treated with the same drugs as for late blight.

Bacterial cancer. The disease most often occurs in protected soil. Wilting begins with the leaves, on which cracks and dark stripes appear, then the entire bush withers. Cancer is indicated by the ugly shape of the fruit, which contains dark and non-germinating seeds. The infection remains in both seeds and plant debris.

Control measures: unfortunately, it is impossible to treat tomatoes affected by cancer. Sick plants should be destroyed as quickly as possible

Particular attention should be paid to healthy seeds

Reasons for appearance

Any plant can become infected; pathogenic spores are transmitted as follows:

1. when watering, when water flows from one bush to another;
2. air flows;
3. on hands and gloves;
4. insects.

The causes of powdery mildew include:

• sudden changes in temperature;
• prolonged rains and high air humidity;
• too dense plantings;
• the presence of weeds in the garden;
• improper watering regime (overmoistening of the soil and its drying out);
• high nitrogen content in the soil.

Where does it come from?

The main reason for the spread of powdery mildew is violation of agricultural practices when growing tomatoes:

Spores are transmitted from sick plants to healthy ones ; they can be carried by water, parasitic insects, through an infected tool or the hands of a vegetable grower.

Signs of the disease

Powdery mildew can be confused with rot or downy mildew. It can be recognized by the course of the disease.

First it affects the lower leaves and gradually moves to the upper part of the bush.

The greens become covered with spots with a mealy structure and a greenish, gray-white or light yellow color.

A characteristic difference from other diseases is the appearance of brown balls on the surface of foliage and young twigs, as well as an increase in the density of plaque and its darkening.

The fight against powdery mildew should be started immediately after the first signs of the disease are detected. Delaying the process will reduce the likelihood of recovery.

Morphology

The causative agent of the disease is Leveillula taurica (Lev.) G. Arnaud - a marsupial fungus with a conidial stage Oidiopsis taurica Salm. (=Oidiopsis sicula; =O.lycopersici).

Conidia are solitary, elongated-elliptical in shape. Size 20–39x11–16 microns.

Conidiophores are elongated, branches extend from the base, forming a secondary, superficial mycelium.

Erysiphe communis (Wallr.) f. sp. solani-lycopersici Jacz is a marsupial fungus with the conidial stage of development of Oidium erysiphoides.

Conidia - connected in chains, elliptical or cylindrical in shape. Size 30–40x15–20 microns.

Conidiophores are short.

How does it develop and why is it dangerous?

Signs of the disease are clearly visible on the bushes; it is important to notice them in time and begin treatment, since powdery mildew develops very quickly and spreads throughout the tomatoes.

Stages of development:

1. The spores land on the lower leaves of tomatoes and form white spots.
2. On the reverse side of the foliage, ring-shaped lesions are formed, their structure reminiscent of flour.
3. Then the disease moves to young shoots, petioles and stalks.
4. Lastly, it affects inflorescences and fruits. Cracks form on the latter, in which rot and white plaque appear.

The disease leads to the death of plants, as well as rotting of fruits. They become covered with brown spots and lose their elasticity. If the gardener is late with treatment, he will lose the tomato harvest.

Fighting powdery mildew on tomatoes with folk remedies

Diseases destroy crops and motivation

So, from the topic of the article it is clear what kind of disease we will be examining today - powdery mildew on tomatoes, which is what is shown in the photo. How to fight, what are the signs and what to do to save the fruits without getting poisoned by chemicals - this is what we will talk about. Powdery mildew is an insidious disease; it affects not only tomatoes, but also other crops and often flowers.

The view in the garden beds becomes dull, but this disease has one advantage, well, if you can call it that, because dew is easy to determine. It really does resemble a coating of flour, as if someone sprinkled the beds and some of the leaves got dirty. But if you don’t take action in time, you can first lose the leaves, and then the entire crop.

Photo

Check out the photo below to see what the disease looks like on tomatoes and seedlings.

How to fight?

There are many known methods for treating powdery mildew on tomatoes, as well as how to deal with it on seedlings. They are conventionally divided into:

• agrotechnical;
• chemical;
• biological;
• folk

Agrotechnical methods

Treatment must begin with the adoption of agrotechnical measures and only then begin to treat the tomatoes with special preparations. For this:

1. Diseased leaves, shoots, flowers and fruits are removed from the bushes and then burned. The same applies to plants that can no longer be saved.
2. Carefully replace the soil under the tomatoes with fresh soil, since it is in it that fungal spores hide.
3. The crop is fed with potassium-phosphorus fertilizers, they increase resistance to the disease.
4. Correct the watering regime if it was previously carried out incorrectly.
5. Remove all weeds from the garden bed.

Folk remedies

Folk remedies can cope with the disease only in the initial stages of its development.
In other cases, they are recommended to be used to treat still healthy bushes, as protection against powdery mildew.

The most effective and popular solutions:

1. Soda-soap solution: dissolve a handful of laundry soap shavings and 25 g of baking soda in 5 liters of water. Treat all bushes with the product every four days until the disease subsides. The soap will coat the foliage and stop the spread of powdery mildew, and the baking soda will kill fungal spores.
2. Mix 5 liters of water and 500 ml of whey, spray the resulting solution on the plants 3-4 times, take a break of 3 days between treatments. The product will cover the bushes and form an impenetrable film, which will block the fungus’ access to oxygen and it will suffocate.
3. Chop two or three heads of garlic on a fine grater, add 2 liters of water and leave for 3 days. Use the product for spraying tomatoes and cultivating the soil in the garden; one procedure per week is enough. Garlic does an excellent job of destroying microorganisms and fungi. It weakens and reduces the activity of their molecules.

Chemicals

Fungicides are used when tomatoes are severely affected by powdery mildew. You can read about the most effective ones in the table.

When using chemicals, you must follow the instructions. Solutions should be used immediately after preparation.

Biological drugs

These products contain live bacteria that have an inhibitory effect on pathogenic fungi. They are safe, so biological products can be used even during the ripening period of tomatoes.

When treating powdery mildew, biological preparations require repeated applications and show lower effectiveness than fungicides. Therefore, they are best used for prevention, protection or treatment at the initial stage of disease development.

The most effective biofungicides in the fight against powdery mildew:

• Fitosporin - 10 g of powder per 5 liters of water, spray the foliage every 10-14 days until the disease recedes.

  The solution should be used no earlier than 1-2 hours after preparation.

• Alirin-B – 5 tablets per 5 liters of water, the solution is used for spraying and watering plants at the root.

  Treatment is carried out 3 times, with an interval of 10-14 days.

Features of treating tomatoes in a greenhouse

Powdery mildew more often affects greenhouse tomatoes than bushes growing in open ground.

This is due to the fact that such plantings are constantly located in confined spaces and conditions of high humidity, and are also located close to each other.

In addition, open ground tomatoes can independently obtain nutrients from the ground, but greenhouse bushes are deprived of this opportunity.

Features of treating powdery mildew in a greenhouse:

1. It is necessary to regularly ventilate the plants and prevent them from thickening.
2. For spraying, less concentrated solutions of fungicides and biological products are used.

Otherwise, eliminating the disease proceeds in the same way as fighting it in open ground. To do this, you can use the same means, as well as agrotechnical and folk methods.

Powdery mildew in greenhouses

Greenhouse tomatoes suffer much more often than open ground plants. This circumstance is due to two factors: increased humidity and temperature inside the greenhouse. Such conditions are ideal for rapid spore growth.

You can prevent tomato disease in greenhouses by taking the following steps:

1. Regular ventilation of the room. In hot weather, all vents and doors in the greenhouse should be open for maximum air access.
2. Timely planting of plants. Each greenhouse tomato must have one stem and a minimum number of leaves.
3. Watering plants at the roots. Moisture on leaves and stems creates a breeding ground for spores.
4. Weed control. The soil under tomatoes should not be overgrown with weeds, under which the fungus will feel at ease.
5. Preventive treatment of bushes with fungicides. Unlike open ground plants, greenhouse tomatoes begin to be treated with fungicides before signs of disease appear, since in an enclosed space the fungus multiplies at lightning speed, and plants can die immediately after infecting even one bush.
6. Autumn and spring treatment of walls and soil with special antiseptics. Particular care should be taken to rinse crevices where spores can live for several years. Experts advise using Peshka-S sulfur bombs to disinfect greenhouses. The smoke penetrates into all possible habitats of disease residues, and crop loss is minimized.
7. Thorough cleaning of the walls of the greenhouse to maximize light access. Through dirt and dusty deposits, the sun's rays practically do not enter the greenhouse, which contributes to the proliferation of powdery mildew spores.

It is also worth thinking about preventing sudden temperature changes. It is worth allowing the tomatoes to become hypothermic several times at night, forgetting to close the door or window into the greenhouse, and the fungus becomes more active. The temperature must be constantly monitored using a thermometer. The optimal temperature range for growing tomatoes is 20-27 degrees with a humidity of no more than 65-70%. Too cold or too warm air weakens plants and makes them defenseless.

Prevention and control measures

To avoid the appearance of powdery mildew, it is important to follow the following preventive measures:

1. Avoid nitrogen-type fertilizers.
2. Treat the bushes monthly with a solution of potassium permanganate.
3. Change the planting site more often, and in greenhouses replace the old soil with new one every year.
4. Control pests as they carry fungal spores.
5. Loosen the soil and remove all weeds to saturate the root system with oxygen.
6. Treat tomatoes with preventative agents, for example, Humate or Raek.
7. Comply with all care requirements.

Do not plant tomatoes in one place for more than 3-5 years in a row.

Tillage

Another preventative measure can be called proper tillage of the soil before planting tomatoes, because it is in it that pathogenic spores are most often hidden.

Disinfection methods:

• Copper sulfate helps kill pathogenic bacteria and microorganisms in greenhouses. To do this, dissolve about 50 g of the product in a bucket of water and water the soil in the fall. This solution can be used once every 5 years.
• Green manures are crops that can improve the condition of the soil, these include oats and mustard.
  They are sown after harvest and wait for germination. In spring, the grass is mowed and buried in the ground.
• You can also use biological products, for example, Fitosporin.
  In spring and autumn, the bed is treated with a solution of 6 ml of product and 1 bucket of water. This volume is enough to spray 1 square. m of land.
• The soil for seedlings is watered with boiling water and dried.

Disinfection of planting material

To reduce the risk of tomato infection with fungal diseases, you need to disinfect the seeds before planting. To do this, you can use the following tools:

1. A solution is prepared from 1 mg of potassium permanganate and 100 ml of water and the seed is soaked in it for 20-30 minutes.
2. Mix 1 ml of a pharmaceutical solution of brilliant green and 100 ml of water, then place the seeds in the resulting liquid for 30 minutes.

If the plants on the site have already become infected with powdery mildew, then the fungus may still remain in the soil. Therefore, it is better to take all preventive measures than to treat the plants in the future.

Treatment with folk remedies for powdery mildew on tomatoes

Previously, people grew crops, and there were no drugs to stimulate growth, destroy pests, or fight bacteria. All solutions were sought using various folk methods. They have not lost their effectiveness, but they have lost their relevance. This is because stores are replete with various chemicals, which helps to quickly solve the problem, but in the pursuit of time we forget about the harm. By spraying with chemicals, we cannot count on an environmentally friendly harvest. It is much better to try traditional methods first. Read on about them.

Soda solutions

Soda destroys fungi and can be used to treat ailments of people and plants. So, pour five liters of very hot water, add a tablespoon with a heap of soda, and rub a small piece of soap here. The soda should extinguish, the soap should dissolve, and the solution should cool. Spray the bushes with it in the morning or evening, but not in the heat, once every three days until the disease subsides.

Treat not only the bushes, but also the soil around them.

Milk serum

It covers the leaves, preventing fungi from growing and multiplying. Plus there is additional fertilizer for the plantings. Spraying is carried out every three days, it will take 3-5 times. The proportions are 1:10, that is, dilute a liter of whey per bucket of water.

Bordeaux mixture and copper sulfate

These two remedies help well against ailments and serve as prevention. The first is diluted per bucket of water - 100 grams, the second - 200 grams per bucket of water. Of course, it is advisable to carry out the treatment not only when you have already noticed the lesion, but for the first time two weeks after planting the seedlings in the ground or greenhouse.

If the plants begin to get sick, then they treat not only them and the soil, but also the area around them and the greenhouse. It is also important to always maintain crop rotation.

Ash

Ash has long been used to treat plant diseases and as a fertilizer. Therefore, it is always better to prepare it in advance before the start of the summer season. The best ash solution is the one that has stood for a week. But during this time, your plantings may suffer greatly. It’s better to have the infusion on hand, use it for prevention, and if your bushes are healthy, then you can simply pour it into the soil as fertilizer and a remedy for parasites. You need to dilute a liter of ash in a bucket of very hot water and let it stand. If you cannot wait, then use the solution immediately after it has cooled.

Powdery mildew can be caused by high humidity in the soil, thickening of plantings, weeds, lack of nutrients or their excess, namely excess nitrogen. Look after your garden.

Potassium permanganate

This solution perfectly destroys all fungi and bacteria. Divide 2.5 grams into a bucket of water and treatment is carried out in the morning or evening every five days until the disease subsides.

Garlic

Garlic has long been valued for its ability to fight all pathogenic environments. We use it when we ourselves are sick, but we can also do it when our garden is suffering. At the same time, garlic does not tolerate many insect pests. Which is a big plus, because diseases and parasites can ruin all efforts over months during the season and deprive the harvest.

Take 2-3 heads of garlic, crush them using a blender or simply crush them through a garlic press. Fill everything with two liters of water, leave the infusion for two days, preferably, and spill the soil and spray the plants.

Are there varieties resistant to this disease?

Due to the emergence of fungal resistance to chemicals and other drugs, breeders began to develop varieties resistant to powdery mildew. These include:

• Tolstoy;
• Swart;
• Marmande;
• Roma;
• Scarlet candles;
• Rambinik.

Compliance with all the rules will significantly reduce the risk of powdery mildew. Proper care and control of plants will help to detect the disease in time and stop it at the initial stage of development.

Biology

Like all powdery mildews, the reproductive organs of Blumeria graminis are represented by antheridia (male gametangia) and ascogones (female gametangia). The antheridium has a two-celled structure, while the ascogon has a unicellular structure. During the process of fertilization, the entire contents of the upper cell of the antheridium move into the ascogon through a special pore (hole). Then a closed fruiting body called a cleistothecia appears around the zygote. Inside it, asci with spores are formed. Having matured, the cleistothecia crack, throwing off the upper part, like a lid. This releases the ascospores.

Erisiphe graminis (= Blumeria graminis) shoots ascospores from the bags at a distance of up to 2 cm. Then they are carried by the wind and, falling on plants that are weakened and susceptible to the pathogen, germinate.

Infection occurs at ambient temperatures from 0°C to + 20°C and relative humidity from 50 to 100%. Higher temperatures, above +30 °C, retard the development of the pathogen. The incubation period of the disease lasts from 3 to 11 days, on average 3–5. Conidia are capable of producing several generations over the summer.

The pathogen is highly specialized, but this does not prevent it from exhibiting noticeable heterogeneity. There are two types of its development: monocyclic and dicyclic.

Monocycle type

Conidial sporulation appears and develops from the phase of third leaf formation until waxy ripeness. The marsupial stage is formed in the phase of the plant emerging into the tube, but the formation of asci with ascospores proceeds slowly. They mature only after the cleistothecia have overwintered.

Dicyclic type

The pathogen overwinters as a mycelium. Conidia are formed in the waxy ripeness phase. The marsupial stage is observed towards the end of tillering – the beginning of booting. Ascospores ripen and are released from August to September. In this case, powdery mildew affects crops in the fall, and carrion seedlings become its reserves.

The plants that suffer most from powdery mildew are those that are shaded and those that are exposed to short periods of light. It has been noted that early spring crops are affected less than later ones. Winter crops are most affected when sown early.