Diseases

Erysiphe betae (Vanha) Weltzien - Powdery Mildew of Sugar Beet.

Systematic position.

Class Ascomycota, order Erysiphales, family Erysiphaceae, genus Erysiphe (Braun U.).

Synonyms.

Erysiphe communis (Wallr.) f. betae Jacz.

Biological group.

Obligate parasite of Sugar Beet.

Morphology and biology.

Plants of beet of the first and second year are affected. Disease appears on all above-ground parts of plant (on leaves, stalks, and glomes of beet) as a white bloom. In the beginning the bloom is gentle and web-like; then it quickly expands, becoming white, dense, and powdering. The affected parts of plants get a powdered kind. In the second half of vegetation the brown, later black dots are formed on a white strike black points of fungal cleistocarpia are formed on white bloom. The affected leaves turn yellow and die off. Primary infection of beet plants is formed by ascospores, which are thrown out from wintered cleistocarpia having size 75-102 microns in diameter; the cleistocarpia form 6-8 asci (62-65 x 35-40 microns in size) with 4-6 ascospores in each one (20-24 x 13-14 microns in size). During vegetation of plants the Powdery Mildew is distributed by conidia being formed on short conidiophores. Conidia are oval, colorless, 30-36 x 10-15 microns in size. The disease results in premature dying of plants, decrease of weight of roots, reduction of sugariness, and bad safety at storage.

Distribution.

Disease is recorded in all areas of industrial cultivation of sugar beet in the former USSR. High severity was reported in Central Black Earth area and Krasnodar Territory (61 to 100% plants were affected), and also in Moldova, Kirghizia, Kazakhstan, Ukraine, and Georgia. Low severity was reported in Oryol, Tula, Saratov, Nizhnii Novgorod, Penza, Rostov Regions, in Mordovia, Chechnya and Ingushetia.

Ecology.

The pathogen winters as cleistocarpia on plant residues, on soil surface, on heads of parent beet, on glomes of beet seeds. The disease intensively develops at sharp fluctuations of humidity (63-93%) and air temperature, being especially developed at dry and hot weather when the average air temperature reaches 20-25. to 34-35.C.

Economic significance.

The disease results in decrease of yield of sugar beet roots by 20-30%, of seeds by 5-16%, of sugariness by 1-5.3%, of seed germinating capacity by 11-38%. Control measures include crop rotation; placement of beet crops at a distance of 1 km and more from seed fields; deep autumn plowing of fields; application of phosphoric-potash fertilizers; agronomical actions directed on improvement of water supply of plants; treatment of crops by system fungicides; dusting by powder of sulfur; use of resistant varieties.

Related references.

Al.khovskaya T.F. 1969. Fungal diseases of sugar beet in Chu River valley of Kirghizia. PhD Thesis. Tashkent, 19 p. (In Russian)
Bondarenko A. 1965. Powdery Mildew of Beet. Kolkhozno-sovkhoznoe proizvodstvo Moldavii 6: 31. (In Russian)
Hawksworth D.L., Kirk P.M., Sutton B.C., Pegler D.M. 1995. Ainsworth & Bisby.s Dictionary of the fungi. CAB International. 616 p.
Kovbasyuk E.V. 1985. Mechanism of development of Powdery Mildew of Sugar Beet in zone of sufficient humidifying in northwest Forest-steppe of Ukraine. In: Zubenko V.F., ed. Effective measures of sugar beet protection from diseases at industrial technology of its cultivation. Kiev, p.17-22. (In Russian)
Lipgardt Yu.Yu. 1981. Powdery Mildew of Sugar Beet in South-East Kazakhstan and ways of reduction of its harmfulness. PhD Thesis. Kiev, 24 p. (In Russian)
Musaev T.S. 1975. Influence of Powdery Mildew on yield and quality of beet seeds. In: Zaprometov N.G., Karimov M.A., eds. Diseases of agricultural crops and their control. Tashkent, iss. 36, p. 85-88. (In Russian)
Popova I.V. 1968. Diseases of sugar beet. In: Polyakov, I.Ya., ed. 1968. Distribution of pests and diseases of grown crops in the USSR in 1967 and prediction of their appearance in 1968. Moscow: Rossel.khozizdat, p. 94-96. (In Russian).
Pozhar Z.A. 1963. Diseases of sugar beet. In: Polyakov I.Ya., Chumakov A.E., eds. Distribution of pests and diseases in agricultural crops in the USSR in 1962 and the forecast of their appearance in 1963. Leningrad: VIZR. p. 218-225. (In Russian)
Zhukova L.M. 1967. Powdery Mildew of Sugar Beet in South Ukraine and its control. PhD Thesis. Kiev, 18 p. (In Russian)

© Khlopunova L.B.