The causative agent: the bacterium Corynebacterium michiganense.
Harmfulness: this disease is considered one of the most dangerous, its first symptoms can be noticed only after the beginning of fruiting. A massive defeat leads to a loss of up to 30% of the crop, as well as often the loss of plants.
Bacterial tomato canker is a disease that is characteristic of plants of solanaceous, which is caused by slow-moving rodlike bacteria-causative agents. They enter the body of tomatoes mainly through external mechanical damage. Basically, it is greenhouse and in the open ground disease is practically not found. The best conditions for the development of this infection are the temperature above 25°C and high humidity. At a temperature of 50°C, the causative agent perishes. There are two types of this disease - diffuse and local.
With diffuse defeat on the petioles of adult tomatoes, longitudinal bands are formed, which eventually turn into ulcers, due to which the stalk of the plant is cracked and it dies off. In this case, the fruits take vulgar forms, their seeds do not give dark and new healthy shoots.
In the case of local damage, small dark spots appear on the above-ground part of the plant, and on the fruit, light blurring with a darkening in the center (often called "bird's eye" due to its characteristic form). In this case, the fruits with this kind of infection develop normally, and the seeds are not infected by the pathogen of the disease.
Infection with this disease is possible only through seeds in which bacteria-pathogens (both externally and internally) are preserved. Among the main symptoms is the fading of leaves with sufficient watering of the crop, while not uniformly, but from one side of the plant. The appearance of an egg ("bird's eye") is possible at the stage of the formation of the ovary and the appearance of the first fruits.
In the course of its development, bacteria penetrate into the vascular system of tomato with a diffuse infection, clogging it. This causes the fading and premature loss of plants.
The root cause of the bacterial canker of tomatoes in a greenhouse can be only infected seeds, because alone the soil pathogen cannot remain for a long time. The risk of contamination through soil, plant residues or garden equipment is significantly lower.
The following measures are recommended as prevention of bacterial tomato canker: