Powdery mildew on tomatoes is the general name for fungal diseases that are characterized by a white powdery coating on the leaves and stems. The main pathogens are marsupial fungi Oidium erysiphoides and Oidiopsis taurica.
Oidium most often affects greenhouse tomatoes with insufficient watering and low relative humidity. In open ground, the disease is possible, but does not have such serious consequences and is easier to treat.
The first signs of the disease are round yellowish spots on the leaves at the bottom of the bush. A white powdery coating is visible on the reverse side. Over time, the spots merge and the plaque moves to the upper parts of the leaves and stems. Fruits affected by powdery mildew crack and rot.
To minimize the risk of powdery mildew on tomatoes, you must adhere to the following rules:
- regular cleaning of the area from weeds, rotten fruits and other plant debris;
- compliance with crop rotation rules on the site and annual replacement of soil in the greenhouse;
- Planting no more than 3–5 bushes per square meter, forming bushes, tying them to supports, removing excess shoots and leaves that interfere with air circulation;
- timely feeding tomatoes mineral fertilizers without exceeding permissible dosages (especially nitrogen);
- timely watering;
- regular ventilation in the greenhouse;
- daily inspection of plantings for the purpose of early detection of infected plants;
- preventive treatment of tomatoes with biological products;
- timely treatment of infected plants with chemicals.
How to fight powdery mildew on tomatoes?
At the first signs of infection of tomato plantings with powdery mildew, it is necessary to react quickly and treat the plants in the first 3–4 days. Fungal infections are easier to treat in the early stages, before tissue necrosis occurs.
If measures have not been taken to combat powdery mildew on tomatoes, fungal colonies will quickly spread. The leaves dry out and fall off. The plant will try to sprout new shoots, but under the influence of infection they will also quickly die.
Smarter 2–3 times a month, carry out preventive spraying of tomatoes with safe biological preparations or compositions from folk practice.
Folk remedies
Before treating tomatoes for powdery mildew with chemical fungicides, you can try treatment with folk remedies. The main thing is to have time to spray the tomatoes in the first 3–5 days after infection.
Soda and soap solution
Mix 2 tablespoons of soda and 10 g of laundry soap into 10 liters of hot water. All tomatoes are sprayed with a cooled solution when the first signs of infection appear in the beds. After 2–3 days, the treatment is repeated.
Milk serum
Whey is diluted with water in a ratio of 1:10 and sprayed on tomatoes in dry weather. The serum dried on the leaves forms a protective film and prevents the development of fungus.
The serum is a safe and effective preventative against powdery mildew. Spraying plants once every 2 weeks will help avoid infection. The initial form of the disease is treated with a course of 3-4 treatments with an interval of 2-3 days.
Wood ash infusion
Wood ash is poured with hot water in a ratio of 1:10, stirred and left for a week. The water is carefully drained without sediment and the tomatoes are sprayed with it. Treating tomatoes with ash solution is an additional foliar feeding with minerals.
Manganese solution
Dissolve 2.5 g of potassium permanganate in a bucket of water and spray the tomatoes every 5 days until the signs of the disease disappear.
Bioactive substances
Not all measures to combat powdery mildew on tomatoes are equally safe for the treated plants, humans and the environment. If the disease is not advanced, then it is better to use harmless bioactive substances.
Humate Na
A solution of sodium humate (0.01%) is suitable for treating tomatoes in the initial stages of powdery mildew infection and for preventive treatments.
Spraying once every 10–14 days at the first signs of the disease stops the spread of the fungus.
Important! Humate, being a growth stimulant and complex fertilizer, helps plants grow stronger and recover from illness.
Thiovit jet, Cumulus DF (colloidal sulfur)
The bioactive substance colloidal sulfur disrupts the vital processes of mealy fungus cells. The result is visible the very next day after treatment and retains its protective effect for another 10–14 days. Subject to the recommended dosage of 30–80 g per 10 liters of water, means is safe for plants. Tomatoes are processed 1–5 times per season.
Biological drugs
By spraying tomatoes with biological preparations, you can not only cure plants of fungi, but also further strengthen their immunity.
Baktofit
Treatment with the biological preparation Baktofit should be carried out for preventive purposes and at the first symptoms of powdery mildew infection. It is harmless, is a good growth stimulator and increases yield by 10–20%. Bactofit can be used in conjunction with chemical herbicides to reduce the likelihood of burns and restore plants.
Planriz
Planriz is not registered, but is widely used by vegetable growers to combat fungi, including powdery mildew of tomatoes. This biological product treats the disease in the initial stages and is suitable for preventive spraying. Treatment is carried out once every 10–14 days. If necessary, Planriz is suitable for tank mixtures.
Bordeaux liquid
Treatment with Bordeaux mixture can be carried out only on cool, dry days, so as not to leave burns on the leaves of the tomatoes. For preventive spraying, a 1% solution concentration is suitable.If signs of fungal disease appear, treatment is carried out with a 3% solution of Bordeaux mixture. Copper in the solution has a positive effect on plant growth and ovary formation.
Chemical fungicides
Chemical fungicides can harm insect pollinators and, when used frequently, cause resistance in fungi.
Advice. Do not treat tomatoes with chemical fungicides more than 2-3 times per season and try to change the active ingredients.
Silicate glue is usually added to solutions for better adhesion of the drug. When spraying, choose a fine spray mode to prevent the substance from flowing onto the soil. In a greenhouse, not only the plants, but also the structure of the structure are treated with fungicides.
Quadris
Quadris belongs to the class of strobilurins. In calm, dry weather in the evening or morning, treat tomatoes with a 0.2% working solution of the fungicide. Do not allow the drug to flow onto the soil. The number of treatments per season should not exceed two.
Topaz
Topaz belongs to the class of triazoles. Active against powdery mildew on tomatoes and other fungal diseases. Topaz is able to penetrate through young shoots into the plant and act systematically in all parts of the bush. The activity of the drug remains for two weeks.
Privent, Byleton
Privent and Bayleton belong to the group of triazole derivatives. The active substance is triadimefon. Broad-spectrum fungicide. If signs of powdery mildew infection are detected, plants are treated with a 0.1% working solution.
Triadimefon penetrates the tissue of tomato bushes and stops the division of fungal cells. The effect of the drug is noticeable already on the first day after treatment and lasts up to 3-4 weeks.
