Diseases

Erysiphe communis Wallr. f. glycine Jacz. - Powdery Mildew of Soybean

Systematic position.

Class Ascomycetes, superorder Pyrenomycetidae, order Erysiphales, family Erysiphaceae, genus Erysiphe.

Biological group.

This species is a biotroph.

Morphology and biology.

The disease is characterized by albescent web-like or mealy bloom on the upper side of leaves, on stems and beans. Later the bloom condenses, turns gray, forming black points of cleistothecia of the pathogen. Cleistothecia are spherical, 62-180 microns in diameter, with numerous simple appendages. One cleistothecium forms 4 or 8 ellipsoidal asci with 8 unicellular ascospores that are 9-14 x 19-25 microns in size. The fungus can produce conidial sporification in addition to the ascigerous stage. Conidia are ellipsoidal, unicellular, singular, located on apices of elongated conidiophores, 8-10 x 25-30 microns in size. Cleistothecia of the fungus winter on infected vegetation residues. Conidial sporification is a mode of spreading for this species during vegetation of plants.

Distribution.

The disease is distributed in Western Europe, Japan and the Ukraine. In the former USSR it is found in the Far East and Northern Caucasus.

Ecology.

Conidia are spread by wind, rain, and insects. Optimum conditions for conidia germination are temperatures of 18-22.C and relative humidity 60-80%.

Economic significance.

The pathogen is highly specialized. Affected leaves have smaller assimilating surface and become fragile. Strong development of the fungus can cause a significant decrease in yield, i.e., by 15% and more. Control measures include crop rotation, destruction of vegetation residues and spraying of plants during vegetation.

Reference citations:

Golovin P.N. 1960. Powdery mildew fungi parasitizing on crops and useful plants. Moscow-Leningrad: AN SSSR. 266 p. (In Russian)
Peresypkin V.F. 1989. Agricultural phytopathology. Moscow: Agropromizdat. 480 p. (In Russian)
Pidoplichko N.M. 1977. Fungal parasites of cultural plants. Guide, V. 1. Kiev: Naukova Dumka. 299 p. (In Russian)

© Kungurtseva O.V.