by Late blight is one of the most insidious diseases of tomatoes. Many gardeners simply give up at the thought that they can be left without a harvest because of late blight. But if you know how this disease arises and develops, it can be prevented or stopped at an early stage.
The causative agents of late blight are fungal-like organisms called oomycetes. Phytophthora infestans, capable of a parasitic lifestyle. Translated from Greek, the word “phytophthora” means “plant destroying”, since the phytopathogen, developing, leads to the complete death of the plant organism.
Late blight is spread by zoospores that overwinter in the soil on infected plant debris. Zoospores are spread by water, wind, insects, and humans, and the disease quickly affects plants both in protected and open ground.
The most favorable conditions for the development of the disease:
- high humidity,
- a large difference between day and night temperatures,
- poor air circulation,
- moderately high air temperature (18-25°C).
How does tomato late blight manifest itself?
Tomato late blight first appears on leaves and stems as gray-brown spots of various shapes with a light green border along the edge. On the back of the leaves, dark areas are covered with a white coating – these are the spores of the phytopathogen. If the disease progresses, it will also destroy the fruits, regardless of their degree of maturity. Dense brown spots of various shapes will appear on them. Tomato fruits affected by late blight turn brown and rot quite quickly.
If you have found the first signs of late blight on individual tomatoes, pick off the affected leaves and shoots, and remove the severely damaged bushes completely. Then proceed to treat the remaining plants.
Never put diseased plants in a compost bin, otherwise the infection may spread throughout the entire area in the future.
How to treat tomatoes
Supporters of organic farming often use biofungicides based on hay bacillus, pseudomonads or the soil fungus trichoderma as a preventive measure. They can be used for treating seeds, soil, roots of seedlings, and for spraying tomatoes during the growing season. Among folk remedies, the most popular are the following:
- Whey solution with iodine. Unpasteurized whey (1 l) is diluted with water (4 l) and 15 drops of iodine are added. Tomatoes are sprayed immediately after the solution is prepared.
- Garlic infusion with potassium permanganate. Grind 100 g of garlic (you can use bulbs, arrows and leaves) and pour 1 glass of water, then leave for 1 hours. After that, strain the mass, add 10 g of potassium permanganate and dilute in 10 liters of water. Spray the plants with the resulting solution every 15-0,5 days. On average, liters are used for each bush.
- Turmeric infusion. 10 g of turmeric powder and 2 g of ground black pepper are poured with 200 ml of vodka and infused for 50 hours. Dilute 5 ml of the infusion in 500 liters of water, adding ml of unpasteurized whey to the solution.
- Wood Ash. Ash is sprinkled between the rows of tomatoes a week after planting the seedlings in the ground or greenhouse. When the fruits begin to set, the dusting is repeated.
- Horsetail decoction. 100 g of dry (or 150 g of fresh) horsetail is added to 1 liter of water and boiled over low heat for 30 minutes. After which the decoction is diluted in 5 liters of water, cooled to room temperature and the plants are sprayed every 10-14 days.
To protect crops from late blight, biological preparations and folk remedies should be used not when the plants show signs of the disease, but in advance. The first time tomatoes are sprayed at the beginning of budding, and the second time – after 10-14 days.
But what to do if you have already noticed the first signs of the disease? Professional products will come to the rescue, which not only prevent, but also effectively suppress phytopathogens, protecting plants for a long time during the growing season.
The drug Provisor is a reliable assistant in the fight against late blight and other diseases of garden and vegetable crops. It begins to act an hour after treatment and protects plants for two to four weeks. The drug is based on azoxystrobin. This is the only fungicide that acts on three large groups of pathogenic fungi and fungus-like protists at once: Ascomycota, Basidiomycota, Oomycota.
Azoxystrobin is a synthetic analogue of natural strobilurins secreted by the fungus. Strobilirus tenacellus, growing on fallen cones. With the help of strobilurins, it destroys all types of fungi that are its competitors and can harm it. Azoxystrobin inhibits the cellular respiration of phytopathogens, preventing them from reproducing and infecting other plants.
The drug Provisor helps to cope with such diseases as late blight, alternaria, septoria, powdery mildew, mildew, downy mildew. It not only fights diseases, but also helps to increase the yield – one treatment is enough. Provisor is a real “first aid” in cases when the ovaries are formed, and the plant is affected by disease. In addition, azoxystrobin has minimal toxicity for mammals, birds, bees and earthworms.
The first spraying with the preparation is recommended to be carried out after 1-2 brushes have blossomed, the subsequent ones – at intervals of 7-14 days. The consumption of the working fluid is 10 l/100 sq.m. It is important to start the treatments in a timely manner to prevent the development of diseases.
Before treatment, it is necessary to remove leaves with signs of disease, as well as shoots and leaves that thicken the bushes and interfere with air circulation.
How to prevent the appearance of late blight
Late blight, like any other disease, is easier to prevent than to treat. Let’s look at the basic rules for caring for tomatoes, which significantly reduce the risk of the disease.
- Choose tomato varieties and hybrids for growing that are relatively resistant to late blight (Alaska, Alpatyeva 905, Banana Legs, Boni MM, Dubrava, Gnome, Gardener, Orange Miracle, Chio-chio-san, Gypsy, Lark F1, Ilyich F1, Resonance F1, Soyuz 8 F1, Ural F1, Charisma F1 and etc.).
- Observe crop rotation.
- Regulate the acidity of the soil (it should be within 6-7 pH).
- Treat the greenhouse in autumn and spring, before planting seedlings.
- Disinfect tools, stakes and material used to tie up tomatoes.
- Do not plant potatoes and tomatoes next to each other.
- Carry out preventive treatments of tomatoes, potatoes and other nightshades.
- Do not thicken the planting.
- Pluck off the lower leaves that touch the soil.
- Ventilate the greenhouse regularly and do not allow air to stagnate.
- Do not apply excessive amounts of nitrogen fertilizers; give preference to phosphorus-potassium fertilizers (especially in the second half of summer).
- Mulch the soil in your tomato beds.
- Water the bushes only at the roots, preferably in the first half of the day.
- Remove weeds in a timely manner.
- After harvesting, carefully remove all plant debris, as this is most often the source of infection.
Try to create and maintain optimal conditions for plants in greenhouses. Carefully inspect tomato leaves throughout the season to avoid missing the first signs of disease.
Take proper care of your green pets, don’t forget about disease prevention – and no late blight will ruin your harvest!
