Diseases

Erisiphe cichoracearum D.C. f. helianthi Jacz., Leveillula compositarum Golow f. helianthi Golow. - Powdery Mildew of Sunflower

Systematic position.

Class Ascomycetes, order Erysiphales, family Erysiphaceae, genera Erisiphe and Leveillula.

Biological group.

Obligate parasite.

Morphology and biology.

These causative agents affect leaves and stalks of sunflower. E. cichoracearum affection appears as a continuous white felt fur mainly on the upper surface of leaves. L. compositarum forms separate angular yellow spots with brown bordering, with mycelium that are partly drowned into vegetative tissue on the lower side of leaves or, sometimes, on their upper surface. During the vegetation of affected sunflower the causative agents form several generations of asexual spores or conidia, which cause new infections on plants. Conidia on mycelium are formed as chains (E. cichoracearum) or individual formations (L. compositarum). At the end of sunflower vegetation, the sexual stage (ascus) appears on affected parts as closed fruiting bodies or cleistothecia (perithecia). The fungus E. cichoracearum has round cleistothecia; their size is 120-122 microns; asci are 58-65 x 30-32 microns, ascospores are 21-24 x 11-13 microns, and conidia are 24-32 x 17-19 microns in size. L. compositarum has flat cleistothecia; their size is 160-250 microns, asci are 72-120 x 27-35 microns, ascospores are 26-38 x 14-24 microns, and conidia are 48-63 x 15-24 microns in size. Perithecia and over-wintered mycelium kept in affected sunflower leaves and stalks are the source of initial infection by the disease causative agents.

Distribution.

Sunflower Powdery Mildew is spread throughout Russia and other countries of the former USSR everywhere.

Ecology.

Renewal of the disease occurs after germination of perithecia and over-wintered mycelium at temperatures between 13-17 degrees C. Powdery Mildew on sunflower is manifested during the flowering period as a rule. It occurs more intensively during dry and hot weather. The infection of sunflower by L. compositarum is mainly noted in droughty regions.

Economic significance.

Strong infection of leaves by Powdery Mildew causes a premature drying of plants which results in decreases of sunflower yield and oil content. The disease causes maximum harm in Kazakhstan, southern steppe regions of Russia, Ukraine, and Moldova. Quantitative harm of the disease is unstudied on sunflower. Resistant varieties and hybrids and also optimum crop rotation are recommended for control against the disease.

Reference citations:

Golovin P.N. 1960. Powdery mildew fungi parasitizing on crops and useful plants. Moscow-Leningrad: AN SSSR. 266 p. (In Russian)
Gorlenko M.V. 1968. Diseases of sunflower. Agricultural Phytopathology. Moscow: Vysshaya shkola. 206-207 p. (In Russian)
Kukin V.F. 1982. Diseases of sunflower and measures of its control. Moscow: Kolos. 80 p. (In Russian)
Maric A., Camprag D., Masirevic S. 1987. Sunflower diseases and pests and their control. Belgrade: Nolit. 379 p. (In Serbian)
Tikhonov O.I. 1975. Diseases of sunflower. In: Pustovoit V.S., ed. Sunflower. Moscow: Kolos. 401-409 p. (In Russian)
Yachevskii A.A. 1927. Pocket handbook on identification of fungi 2. Powdery mildew fungi. Leningrad. 258-259 p. (In Russian)

© Yakutkin V.I.