The causative agent: fungi of the genus Fusarium: fungi of the genus Fusarium: Fusarium oxysporum f. Sp Lycopersici, F. moniliforme, less often F. nivaie and F. solaria.
The disease is common in warm countries. The disease is a particular danger for soil greenhouses with acidic sandy soils, where pathogen can be preserved. Symptoms of the disease are similar to those of other diseases; therefore, it is difficult to initially accurately determine the cause of the disease of tomato and start correct treatment. The causative agent penetrates into the plant through the roots, clogs the vessels, which leads to slowing its growth, stopping the development of fruits and dying out.
Fusariosis wilt of tomatoes is more typical for greenhouse plants, which from season to season are grown in the same soil. The disease can manifest itself at any stage of the plant's development. After infection, its immunity decreases, which increases the possibility of penetration of other diseases. Comfortable conditions for the development of this disease are sharp differences in temperature and humidity levels, insufficient illumination, as well as mechanical damage to the stem and root system of the plant.
The fungus penetrates the vascular system of tomato through young, not yet strengthened roots and develops along with the plant. The disease usually appears during the period of mass fetal growth of tomato, when the load on the plant increases and its immunity is reduced. Identify it after the manifestation of the primary symptoms (yellow and fading leaves), it is possible to cut the stem - angio of plant will be brown. To confirm the "diagnosis" it is enough for a couple of days to hold the cut stem in a place with high humidity - in such conditions will begin to appear white mycelium.
As the fungus develops in the vascular system of the tomato, the lower layers of the leaves first yellow, and then the top. Sheet streaks are lightening. The leaves themselves are deformed, twisted and fall off. In wet weather, you can see a white scarf on the roots of dried plants. At high temperature, the disease progresses more intensively. With time, the whole plant will dry up and die.
One of the main causes of infecting the pathogen of the disease into a plant is damage to the root or wound on tomato during ticking. The spores of Fusarium can live both in the soil itself and on the surface of the inventory that it undergoes, as well as in the seeds and substrate for seedlings. But if there is no agent in the soil, then there is nothing to fear.
The secondary causes of the development of fusarium wilt of tomatoes are excessive plant density, poor light, poor watering, breaking the rules of crop rotation, excess chlorine and nitrogen fertilizers in the soil. As a prevention there are such actions: regular disinfection of soil and seeds before planting, strict adherence to agrotechnical norms of tomato breeding and rules of crop rotation, treatment with biological and chemical preparations, as well as the creation of favorable conditions for the growth of tomato, but destructive to the development of the disease.