The pathogen responsible for the disease is the imperfect fungus Cercospora beticola Sacc., which possesses high genetic plasticity and is represented by numerous regional pathotypes. The infection manifests as small, circular spots 2–4 mm in diameter, grayish-brown in color with a reddish-brown border. Under conditions of high humidity, a characteristic velvety coating of fungal sporulation forms in the center of the spots.
The infestation begins with the lower leaves and gradually spreads to the entire rosette, and in cases of high infection intensity, to the petioles and seed plant stems. Severe disease development causes premature wilting and death of the leaf blade. This triggers secondary foliage growth at the expense of sugar stored in the root crops, leading to yield loss and reduced storage quality in piles.
Genetic resistance to Cercospora leaf spot in sugar beet is a complex trait controlled by the NBS-LRR gene family. Currently, there are no immune cultivars; therefore, breeding efforts are focused on developing tolerant hybrids capable of limiting pathogen development in various geographical zones.