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Late blight called the tomato plague, the most terrible disease of nightshades, it is from this disease that the entire tomato crop can die. As long as gardeners cultivate tomatoes, their “war” against late blight lasts. For decades, farmers have been coming up with new ways to combat the causative agent of tomato disease; there are a variety of remedies for this disease: from the use of medications to completely exotic methods, like copper wire on the roots of tomatoes or sprinkling the bushes with fresh milk.
What is late blight, how can it be treated and what causes this disease? And, most importantly, are there varieties of tomatoes that are resistant to late blight? These issues are discussed in this article.
How dangerous is late blight for tomatoes and what causes it?
Late blight is a disease of plants of the nightshade family, which is caused by the fungus of the same name. The disease manifests itself in the form of watery spots on tomato leaves, which quickly darken and turn brown.
The fungus quickly spreads throughout the plant, following the leaves, the stems and then the tomato fruits become infected. Late blight of the fruit appears as a compaction under the skin of the tomato, which darkens and becomes larger. As a result, the entire fruit or most of it turns into a deformed brown substance with an unpleasant putrefactive odor.
The danger of late blight lies in the excessive vitality of fungal spores and their very rapid spread. In just a few weeks, a gardener’s entire crop can be destroyed; sometimes no methods of combating this disease are effective.
The environment in which spores are stored and propagated is soil. Late blight is not afraid of either extreme heat or low winter temperatures - contaminated soil in the new season will again contain spores and pose a danger to any plants of the nightshade family.
There is also no need to plant potatoes close to the beds with tomatoes, because this crop contributes to the very rapid spread of late blight.
The following factors can awaken late blight spores dormant in the ground:
- low temperature in the summer season;
- lack of air, poor aeration of tomato bushes;
- high humidity is an excellent environment for the proliferation of microorganisms;
- excess dose of nitrogen fertilizers;
- lack of elements such as potassium, iodine and manganese in the soil;
- shade or partial shade on the site, the predominance of cloudy weather;
- excessive watering;
- the growth of weeds between tomato bushes;
- moistening the stems and leaves of tomatoes.
In order for the fight against late blight to have a result, it is first necessary to eliminate all factors contributing to the development of the fungal disease.
Late blight in beds and greenhouses
It is believed that the peak of late blight disease occurs in late summer - August. This month, the nights become cool, the temperature drops to 10-15 degrees, the long rainy season begins in most regions of the country, and there are more and more cloudy days.
All this suits the fungi perfectly - the spores begin to multiply rapidly, capturing an ever larger area.
Farmers consider early varieties of tomatoes to be a salvation from late blight. It cannot be said that tomatoes of these varieties are resistant to late blight; it’s just that the fruits on such plants have time to ripen before the outbreak of the epidemic and “overshoot” the peak of late blight.
However, the climate of not all regions of Russia is suitable for growing early-ripening tomatoes in garden beds - in most parts of the country, summers are short and cool. Therefore, early varieties are often planted in greenhouses.
It would seem that this is salvation from the terrible tomato disease. But, unfortunately, everything is not so - in closed greenhouses the risk of developing the disease is even higher; this is facilitated by the microclimate of the greenhouse. There is a particular danger:
- poorly ventilated greenhouses;
- too thick plantings, unplanted tomatoes;
- high humidity;
- too high a temperature combined with frequent watering;
- soil contaminated by previous plantings in greenhouses;
- watering is not of the root type - only the ground under the bushes can be moistened, the plants themselves must remain dry.
The fact is that fungal spores are perfectly preserved in wood, awakening every season and infecting plants. Wood processing is ineffective; only super-early hybrid tomatoes, which have the highest resistance, are planted in these greenhouses.
That's why selecting late blight-resistant tomato varieties for a greenhouse is an even more difficult task than finding tomatoes for open ground.
Which varieties of greenhouse tomatoes are resistant to late blight?
No matter how hard breeders and botanists try, tomato varieties that are absolutely resistant to late blight have not yet been developed. Every year new blight-resistant varieties appear, but so far there is no tomato that is 100% guaranteed not to get sick with fungus.
But there is a group of tomato varieties that can theoretically develop late blight, but for this to happen several factors must coincide (for example, high humidity and low temperature or planting plants in a wooden greenhouse contaminated with spores).
Determinate tomatoes have the following features:
- grow to the third or fourth ovary and stop developing;
- their fruiting is extended;
- the fruits are of unequal sizes;
- the bushes do not have or have a small number of side shoots, so the plantings are not thickened and are well ventilated;
- give good harvests;
- often distinguished by early ripening.
Unlike low-growing varieties, indeterminate tomatoThey grow up to 1.5-2 meters, have many stepsons, are distinguished by later ripening and simultaneous fruit production. It is better to grow such plants in greenhouses, but it is necessary to monitor the humidity inside and frequently ventilate the greenhouse. It is tall tomatoes that are more suitable for growing for commercial purposes - the fruits are the same size, ideal in shape and ripen at the same time.
"Resonance"
The variety is one of the few indeterminate tomatoes that can resist late blight. An early ripening crop produces fruit within three months after planting.
The bushes are not very tall - up to 1.5 meters. The tomatoes are large, round, red in color, average weight is about 0.3 kg.
The culture tolerates extreme heat and lack of watering. Tomatoes can be transported, stored for a long time, and used for any purpose.
"Oak"
Determinate tomato, compact bushes - up to 0.6 meters high. Early culture - fruits can be picked 2.5 months after planting the seeds. The tomatoes are small in size, colored red, spherical in shape, and weigh about 100 grams.
This variety is considered one of the most resistant to late blight, tomatoes ripen smoothly, and the crop yield is high.
"Dwarf"
The bushes are small, growing to a maximum height of 45 cm. The culture is early, tomatoes ripen in 95 days. The tomatoes are small, about 50-60 grams each, round and red.
There are few lateral shoots on the bushes, so there is no need to pinch them. The variety gives good yields - about three kilograms of tomatoes can be harvested from each plant.
"Orange Miracle"
The crop is tall, with an average growing season; harvesting is necessary after 85 days.Tomatoes are colored deep orange, spherical in shape, but slightly flattened. The color of tomatoes is due to the high content of beta-carotene, which is why tomatoes are very healthy.
The tomatoes are large, weighing about 0.4 kg. Plants resist late blight well and can be grown in hot and dry regions.
"Nobleman"
The bushes are of a determinate type, their height is maximum 0.7 meters. Tomatoes ripen in medium terms and withstand difficult climatic conditions.
Tomatoes are round and large, weight can be 0.5 kg. The pulp of the fruit is sweet, sugary, very tasty.
Bushes of this variety must be pinched, removing lateral shoots.
"Lark"
The variety is a hybrid type, characterized by ultra-early ripening. The culture is resistant not only to late blight, but also to several other diseases that are dangerous for tomatoes.
The bushes are of a determinate type, however, their height is quite large - about 0.9 meters. "Lark" produces good harvests. The tomatoes are medium-sized, weighing about 100 grams. The fruits are considered tasty and suitable for processing and preservation.
"A little prince"
Low growing plant with compact bushes. The productivity of tomatoes is not very high, but the crop resists late blight. The main protection of these tomatoes from a dangerous fungus is a short growing season; the tomatoes ripen very quickly.
Tomatoes weigh a little - about 40 grams, have a good taste, and are great for pickling.
"De Barao"
Indeterminate tomatoes that need to be grown in greenhouses. Plants stretch up to two meters and need to be strengthened with supports. The culture has a strong immunity against late blight; even despite the late ripening period, this variety rarely suffers from fungal diseases.
Tomatoes ripen four months after sowing, have a plum-shaped shape, and weigh about 60 grams. A distinctive feature is the very rich cherry hue of the fruit; sometimes the tomatoes are almost black.
Up to five kilograms of tomatoes are harvested from a bush; they can be stored for a long time and used for any purpose.
"Cardinal"
The greenhouse crop, growing up to 180 cm, has an average growing season. The fruits are distinguished by an interesting heart shape and heavy weight - up to 0.5-0.6 kg. The variety gives good yield and has high taste.
Late blight will not affect these tomatoes if the greenhouse is well ventilated and excessive humidity is not allowed inside it.
"Carlson"
These tomatoes will ripen 80 days after planting. The bushes are quite tall - up to two meters. The shape of the tomatoes is elongated, there is a small “spout” at the end of the fruit, they weigh about 250 grams.
From each such tall bush you can harvest up to ten kilograms of tomatoes. Such tomatoes are stored for a long time, can be transported, and are very tasty.
How to deal with late blight
As mentioned above, late blight is easier to prevent than to overcome. This is a very persistent disease for which it is difficult to find a “treatment”. To identify the disease in the early stages, the gardener should check the bushes and leaves daily, pay attention to light or dark spots on the leaves - this is how late blight begins to develop.
It is better to remove an already diseased tomato bush from the garden so that neighboring plants do not become infected. If most of the tomatoes are affected, you can try to cure these plants. For these purposes, many means are used, in some cases some “medicines” help, in others they turn out to be absolutely useless, then you need to try something else.
Modern gardeners most often use such means from late blight:
- “Baktofit”, diluted in water according to the instructions, and applied under the bush along with watering;
- fungicidal drugs used to irrigate bushes;
- Bordeaux mixture;
- copper chloride;
- folk remedies such as iodine, milk, mustard, manganese and even brilliant green.
You can help plants resist late blight at all stages of development. For this:
- Treat tomato seeds with a manganese solution before planting.
- Spill the soil with boiling water or potassium permanganate, fungicidal preparations.
- Water the bushes only at the roots, carefully ensuring that drops of water do not fall on the leaves.
- In rainy and cool weather, monitor the plants especially carefully and regularly treat the bushes.
- Mulch the soil between tomato bushes.
- Stop any treatment 10-20 days before fruit ripening.
- Plant mustard and basil between the rows of tomatoes - these plants kill late blight spores.
- Remove tomato leaves that touch the ground.
- Tie the tomato stems, raising the plants so that they are better ventilated.
Phytophthora-resistant tomato varieties are not a 100% guarantee of a healthy harvest. Of course, such tomatoes are better able to resist the pathogen; their natural resistance has been greatly enhanced by breeders. But only an integrated approach to the problem of late blight can be considered truly effective:
- purchasing resistant varieties;
- seed treatment;
- soil disinfection;
- compliance with the rules of growing tomatoes;
- timely and regular treatment of plants.
This is the only way to be confident in your tomato harvest!
