Vascular bacteriosis. A characteristic sign of cabbage disease is the darkening of the veins of the leaves, the conducting vessels of the petioles and the stoker.
Bacteria penetrate into the vascular system during the growing season either through water pores located along the edges of the leaf blade or through the roots. In the first case, the infection, falling into droplets (using insects or wind, etc.), is drawn into the pores with them, penetrating the vascular system of the leaves in this way. At the same time, the small veins darken, and the central skeletal veins of the leaves remain with a natural color, the leaves begin to mucus and rot from the edges.
This type of lesion is caused by improper excess watering, especially in the evening, due to which excess water comes out at night in the form of droplets through the water pores. In the second case, bacteria spread throughout the plant from the bottom up (from the roots) – first, they are found in the stumps, and then in the petioles and main leaf veins. Spreading through the vessels of the leaves to the periphery, the bacteria cause the formation of a clearly visible black mesh of darkened veins. The harm from the disease is expressed not only in a decrease in the quality of heads of cabbage but also in a decrease in yield.
Control measures include following crop rotation, carefully discarding seedlings (using only viable seedlings with well-developed roots for planting), and collecting and destroying post-harvest plant debris as the main source of infection.