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any one of several plant diseases caused by fungi imperfecti of the genus Fusarium. The diseases affect both cultivated and wild plants and occur in all climatic zones. Fusarium wilts damage the vascular system and tissue of the plant, causing the rotting of roots, fruits, and seeds and the wilting of ears and cobs. The pathogens live for a long time in the soil and on plant residue as mycelia, chlamydospores, or perithecia; they enter a plant through the root system and lower stalk. Infected seeds and seedlings may also be a source of infection. Rapid development of the disease is aided by adverse abiotic factors, including abrupt fluctuations in air and soil temperature and moisture content, inadequate soil nutrition, and insect damage.
Fusarium wilts cause sudden failure of the vital functions of the affected plants. The mycelium of the fungus clogs the vascular system and secretes fusaric acid, lycomarasmine, and other toxic substances. In most affected plants the leaves lose turgor, turn yellow, curl, and fall off; the top of the plants wilts and withers. Growth is retarded, vitality decreases, and large areas of crops frequently die. Fusarium wilts are especially harmful to fine-staple varieties of cotton, flax, cabbage (primarily head cabbage), gourd crops, grain legumes (mainly alfalfa, soybeans, and feed legumes), potatoes, tomatoes, and eggplant.
Fusarial root rots damage plants at all stages of development. In cereal grains they cause the development of empty ears and shrunken kernels, the death of productive stalks, and, if infected early, the death of shoots. In legume grasses the roots turn brown and decay; the base of the root neck, the central cylinder, and the vascular bundles of the stalk are destroyed.
Fusarium wilts of the ears and kernels of cereals cause the spikelets to turn white and then brown. Nonviable caryopses form. Pale pink or white spots produced by the mycelium form on affected corn cobs at the beginning of full ripeness. In the center of the spots the caryopses turn muddy brown and crumble easily. Seeds damaged by the disease cannot germinate.
One type of fusarium wilt, snow mold, is harmful to winter wheat and rye and to perennial gramineous grasses. Indistinct watery spots produced by a mycelium appear on the leaves. The mycelium spreads over the leaves, cementing them together. Diseased plants often die. Fusarium wilts of coniferous trees, including spruce and pine, also occur.
Control measures include crop rotation, cultivation of disease-resistant varieties, removal and burning of plant residues, dressing of seeds with granozan and mercurane, application of pesticides to crops, and use of healthy seeds and seedlings. Also effective are the application of increased amounts of phosphorous and potassium fertilizers and the liming and draining of soils.
REFERENCESRaillo, A. I. Griby roda Fuzarium. Moscow, 1950.
Gorlenko, M. V. Sel’ skokhoziaistvennaia fitopatologiia. Moscow, 1968.
Peresypkin, V. F. Sel’ skokhoziaistvennaia fitopatologiia. Moscow, 1969.
M. V. GORLENKO