plant diseases caused by various species of fungi of the genus Phoma of the class Fungi Imperfecti of the order Pycnidiales.
In cabbage. The stems of diseased adult cabbage plants develop depressed spots; in storage a dry rot appears on the stock stumps. Seed plants develop gray spots with pycnidia on the leaves, stems, and pods. Sources of infection are plant remains, seeds, and stock stumps. Control measures include heating seeds in water at temperatures of 48°–50°C for 20 minutes, discarding diseased seedlings, separating one-year-old and two-year-old plantings, and removing plant remains from fields.
In carrots. Phomosis appears in the form of a dry rot of the roots of carrots during storage. The stems of the seed plants have dark stripes and spots with a lilac-gray tinge; the stripes and spots later turn gray and develop pycnidia. Sources of infection are plant remains, diseased stock roots, and seeds. Control measures include presowing seed dressing, application of increased doses of potassium-phosphate fertilizers, proper root storage, disinfection of roots before storage and repeatedly in the spring before planting, application of fungicides on seed plants, and removal of plant remains from fields.
In potatoes. Depressed spots or ulcers appear on the tubers of potatoes in storage. In cuts the diseased tissue is brown, almost black along the margins; pycnidia of the fungus protrude through the skin of the tuber to the surface of the spots. Whitish spots with pycnidia appear on the stems. Sources of infection are infected tubers, plant remains, and soil. Control measures include discarding diseased tubers, seed tuber chemical dressing, and removing plant remains from fields.
In sugar beets. Spots appear on the leaves, and dry rot occurs on the roots of sugar beets. Stems and seed plants are affected. Sources of infection are plant remains and seeds. Control measures include seed dressing, applying complete mineral and borate-datolite fertilizers, separating one-year-old and two-year-old plantings, and removing plant remains from fields.
REFERENCESGerasimov, B. A., and E. A. Osnitskaia. Vrediteli i bolezni ovoshchnykh kul’tur, 4th ed. Moscow, 1961.
Dement’eva, M. I. Fitopatologiia. Moscow, 1970.
M. I. DEMENTEVA