Late blight of tomatoes. Prevention and control measures
In recent decades, the scourge of our gardens has become an unpleasant disease called late blight. When you first encounter it, you catch yourself thinking: is it worth growing tomatoes at all, if so much effort is so simple, they come down to zero result. However, late blight, or late blight, is still not the worst thing that can happen to our beds. If you know the characteristics of the disease, it can be prevented, saving yourself from grief and disappointment.
- Signs of late blight of tomatoes
- What contributes to the development of late blight?
- Preventive measures against late blight
- Chemical agents for the control of late blight
- Microbiological agents
- Folk remedies against late blight
Signs of late blight of tomatoes
Late blight or brown rot of tomatoes is a fungal disease caused by the simplest microscopic fungus Phytophthora infestans. It manifests itself in the form of elongated dark brown spots or stripes on the stems and petioles of plants, grayish brown on leaves and brownish brown on fruits.
Starting from the lower tiers of leaves, late blight gradually captures the entire tomato bush. In dry weather, the affected areas dry out, in wet rot.
On fruits, regardless of their degree of maturity, late blight spots have a solid structure. Growing to the entire surface, they affect not only the outer integument of the tomato, but also go deep into its tissues. May appear on ripped tomatoes left for ripening. Inflorescences affected by late blight, flowers and sepals blacken and dry.
What contributes to the development of late blight?
The areas of spread of late blight are quite wide and are divided by severity into strong, medium and weak. However, if even the probability of the spread of this disease in your area is small - to know that blight is necessary, because in addition to tomato, it affects eggplant, pepper, and potatoes, and sometimes it can even be found on strawberries. Damage caused by Phytophthora infestans often results in up to 70% yield loss.
A favorable period for the progression of late blight is the second half of summer, characterized by differences in day and night temperatures and increased humidity in the evening and morning. A banal excess of nitrogen, introduced under the crop during feeding, and poor ventilation of the beds, and high planting density, and the presence of diseased plants among neighboring crops can provoke the disease. Therefore, it is better not to wait for a favorable moment for the fungus, but to take care in advance to protect your tomatoes from it.
Preventive measures against late blight
1. The simplest preventive measure in the fight against late blight, recommended in most literary sources, is the choice of varieties resistant to this disease. But, neither tomato varieties nor hybrids are fully resistant to late blight, no matter what the producers write on packs with seeds. Some agronomists include relatively stable varieties: "Liana", "Glory to Moldova", "Grotto", "Gribovsky 1180", "Cinderella" and some others.
2. You can plant tomatoes with a short growing season and differing in a quick friendly return of the crop, such as Profitable, Radical, F1 Debut, Sanka. Managing to form fruits in 80 - 90 days, they actually avoid the fate of being destroyed by a malicious fungus.
3. The choice of tall varieties also helps to protect against late blight. Their agricultural technique is based on the method of removing the lower leaves, which means that their plantings are more ventilated and less exposed to excessive moisture.
4. Good performance is given by growing crops in greenhouses, where it is easier to maintain a stable temperature and humidity. If there is no way to organize a greenhouse, it is possible, with the onset of cold nights, to cover tomato plantings with foil in the evening.
5. As a preventive measure against late blight, before sowing in open ground or cups, tomato seeds must be pickled with a 1% solution of potassium permanganate.
6. If late blight still “walked” around the garden, the autumn cleaning of the beds should be especially thorough: plant debris should not just be collected, but buried in the ground or burned, and garden equipment should be disinfected.
7. When approaching the dangerous period, you need to monitor the cleanliness of tomato plantings from weeds, to prevent moisture from getting on the leaves during irrigation, to fertilize with a high content of potassium and spray with boric acid (1 tsp per 10 l of water). Subsequently, the spraying is repeated two more times with an interval of two weeks, until the fruit redness.
8. The use of growth regulators on tomatoes shows good results. "Epin plus", "Oksigumat", strengthening plants, give them the strength to resist fungus.
9. The recommended preventive measure is the removal of the lower leaves, as they have the property of “picking up” this disease.
10. At the first manifestations of late blight - affected plants, it is imperative to pull out and remove from the garden.
11. If late blight has come to neighboring areas and the weather is favorable for its development, you can not wait for it to damage your crop, but take off the unripe fruits and put them on ripening, having previously disinfected them in hot water. Dosing should take place in the dark, at a temperature of approximately + 25 ° C, disinfection - for two minutes in water with a temperature of + 60 ° C.
12. Some gardeners, as a preventive measure, use an infusion of garlic (1.5 cups of chopped garlic, 1.5 grams of potassium permanganate and about 2 tablespoons laundry soap per 10 liters of water). The first spraying is carried out when the seedlings planted in the soil take root well (approximately 10-14 days after planting), the second and subsequent are repeated after two weeks, at the rate of 150 g of solution per plant.
However, all this is only the prevention of the disease, and relying on the fact that late blight is a difficult problem, it is impossible to dwell on these measures, but without fail add more substantial control measures to them.
Chemical agents for the control of late blight
Based on the fact that the first signs of late blight, manifested on tomatoes, are an indicator that the disease has already begun to progress (i.e. the fungus has been living in the plant tissues for some time), it is necessary to start fighting it, even by chemical means, in advance - how only the thermometer began to fall to + 10 ° С, strong dew began to appear on the plants or it rained for more than two days. It can be August or September, more often the end of July, and sometimes June.
It is necessary to choose drugs with a reference to the fact that Phytophthora infestans very quickly develops resistance to chemistry, which means taking funds with different active ingredients. Treatments should be carried out once a week, alternating preferred fungicides. What to apply, it is better to inquire about the place of purchase. Since scientists pay increased attention to late blight, new drugs are constantly appearing on the market. Of the old, proven, you can recommend "Bravo", "Ditan", "Ditan M-45", "Ridomil Gold."
Chemical prophylaxis should be carried out in the evening, in the absence of wind. The last spraying should take place no later than 20 days before harvest.
Microbiological preparations, such as Fitosporin and Trichodermin, are also quite an effective option. The microorganisms present in them actively suppress the phytophthora fungus, and the antibiotics secreted by the fungus Trichoderma lignorum also destroy the pathogenic bacteria of other pathogens. However, they will not be able to completely destroy the brown rot of tomatoes, so they must be used in conjunction with other methods of control and prevention.
Folk remedies against late blight
Since we still grow tomatoes "for ourselves", we can try in opposition to late blight and folk remedies. Their scientific justification is insufficient to recommend, but still ...
1. Pine shoots. Finely chop still sticky tops of overgrown pine twigs and boil them for 2 to 3 minutes in 300 to 400 ml of water. Dilute the cold filtered broth with clean water 1 x 5 and spray the tomatoes.
2. Ash. Boil approximately 300 g of ash for about 30 minutes in a small amount of water. Settle, strain, dilute in 10 l of water with the addition of 20 g of grated soap.
3. Rotten straw. On 10 l of water 1 kg of rotten straw or hay, a handful of urea - insist 3 to 4 days. Spraying is carried out with an interval of 1.5 weeks.
4. Copper sulfate. For 10 liters of water, 2 g of copper sulfate and 200 g of soap.