Diseases
Sclerospora spp. . Downy Mildew of Maize
Systematic position.
Class Oomycota, order Sclerosporales, family Sclerosporaceae, genus Sclerospora. Several species of Sclerospora were described: S. maydis, S. graminicola, S. macrospora.Biological group.
Hemibiotroph.Morphology and biology.
Infection by S. maydis causes the formation of light yellow spots on leaves with film on lower surface. The film consists of fungal conidiophores and mass of conidia. The conidiophores are colorless, with short branches forming conidia. The size of conidiophores is about 150mkm. The conidia are ellipsoid, colorless, 28-45 x 16-23mkm. Infection by S. graminicola causes rolling of leaves, making them lighter. Fungal conidiophores are visible in stomata on the lower leaf surface. The conidiophores are ramified, with short branches, forming capitate crown. Conidia are globe-shaped or egg-shaped, colorless, 18-22 x 12-18mkm. Oospores are yellow-brown, rounded-angular, 35-45 mkm in diameter. Ripening, the oospores destroy leaf along ribs and come out. Infection by S. macrospora causes hypertrophy and rolling of leaves; panicles become green. Conidiophores and conidia are absent. Oospores are globe-shaped, colorless, 60-65 mkm in diameter. Initial infection is caused by oospores keeping on infected plant debris. Secondary infection is caused by fungal conidia. Corn plant is very sensitive to the infection in stage of seed sprouting and during period of formation of 3-4 leaves.Distribution.
Sclerosporosis occurs on corn leaves and stem in Kuban region and in Ukraine, but being not very abundant. In Russia S. graminicola and S. macrospora are spread on Setaria italica and Italian millet. The disease is distributed in humid and warm regions.Ecology.
High humidity is necessary for development of these fungi. Thick plaiting of corn is favorable for the disease development.Economic significance.
Under favorable conditions of development the disease can fully destroy yield. The main methods of plant protection are agronomical measures, e.g., ventilation of rows and decrease of soil moisture.Related references:
Kalashnikov K.Ya., Shapiro I.D. 1962. Pests and diseases of maize. Leningrad: Sel.khozgiz, 189 p. (in Russian).Nemlienko F.E. 1957. Diseases of maize. Moscow: Sel.khozgiz. 230 p. (in Russian).