Diseases

Erysiphe communis Grev. f. pisi Dietrich - Powdery Mildew of Pea.

Taxonomic position.

Class Ascomycetes, group of orders Pyrenomycetidae, order Erysiphales, family Erysiphaceae, genus Erysiphe.

Synonym.

Erysiphe pisi DC.

Biological group.

Biotroph.

Morphology and biology.

Infected vegetation residues containing asci are sources of the infection. The disease appears on leaves and beans. The fungus forms a white arachnoid bloom that later turns gray. Leaves roll and die off. Affected young beans do not set seeds; late infection results in the formation of deep ulcers on valves. The fungus spores during vegetation by conidia (anamorph) and asci (teleomorph). Anamorph forms several generations of conidia infecting healthy plants. Conidia are distributed by wind, drops of rain, and insects. Conidia are unicellular, colorless, elliptic, 28-44 x 17-18 microns in size. Ascostage appear at the end of vegetation as yellowish or dark-brown cleistothecia. Fruit bodies are spherical, to 160 microns in diameter, with numerous (10-28) appendages. Appendages are colorless, located radially, with blunt apical branches. Asci ellipsoid, narrowed downward, with 4-6 ascospores. Ascospores unicellular, colorless, 16-22 x 9-12 microns in size.

Distribution.

Disease is distributed in Europe including Great Britain, in USA, Canada, India, New Zealand, Japan. In Russia, Byelorussia, Ukraine the Powdery Mildew is distributed on peas everywhere.

Ecology.

Fungus spreads through conidia by means of wind, rain and insects. Optimum conditions for conidia germination include temperature 18-22.C and relative humidity 60-80%. Incubation period of the disease lasts 4-5 days. In northwestern, western and central areas of the Non-Chernozem region the disease usually appears at the end of summer under damp cool weather conditions. In southern areas the disease appears much earlier, spreading widely under conditions of low humidity and high temperature. Precipitation inhibits disease development.

Economic significance.

The pathogen can infect vetch (Vicia sativa L.), fodder beans (Vicia fabae L.), and to a lesser extent peavine (Lathyrus pratensis L.). High severity (90-100 %) results in a decrease of yield by 5 times. Content of protein is also reduced. Control measures include cultivation of resistant varieties of peas, early terms of sowing, application of potash and phosphoric fertilizers, destruction of vegetation residues, fungicide treatments of plants.

Reference citations.

Golovin P.N. 1960. Powdery mildew fungi parasitizing on crops and useful plants. Moscow-Leningrad: AN SSSR, 266 p. (in Russian).
Iminov I. 1967. Powdery Mildew of Pea. In: Yakhontov V.V., ed. Pests and diseases of fodder and leguminous plants. Tashkent. P. 118-126 (in Russian).
Kitsko V.I. 1972. Powdery Mildew of Pea in conditions of Ukraine and description of resistance of zoned and perspective varieties. PhD Thesis. Kiev. 25 p. (in Russian).
Makasheva R.Kh. 1973. The pea. Leningrad: Kolos. 312 p. (in Russian).
Shvetsova A.N., Vinogradova N.I. 1971. Diseases and pests of field cultures in Western Siberia. Omsk: Omsk Agric. Inst. 171 p. (in Russian).

© Kungurtseva O.V.