Diseases

Erysiphe communis (Wallr.) f. solani-lycopersici Jacz. and Leveillula taurica (Lev.) Arnaud - Powdery Mildew of Tomatoes

Systematic position.

Division Ascomycota, order Erysiphales, family Erysiphaceae, genus Erysiphe.

Synonyms.

Erysiphe orontii Cast., Golovinomyces orontii (Cast.) Geljuta.

Biological group.

Obligate parasite.

Morphology and biology.

Plants during all growth stages of their development, from the appearance of the first leaves until fruiting, are affected. The disease appears on the upper side of leaves and on stems as a white bloom of sporification later turning a brown color. During vegetation the Powdery Mildew is spread by conidia. E. communis f. solani-lycopersici forms conidia on simple short conidiophores being 100-300 microns in length; conidia oval, colorless, 36.6 x 20.2 microns, located one by one or in short rows. Cleistocarpia of the fungus are 65-180 (90) microns in diameter, saucer-shaped, with various numbers of appendages of various shapes. Cleistocarpia form ovoid or rounded asci (46-72 x 30-45 microns) with 3-6 elliptic ascospores each (19-35 x 9-14 microns). L. taurica is found in southern areas only, developing in the conidial stage only (Oidiopsis taurica). Conidiophores are simple, less often weakly branched, 200-700 microns in length; conidia clavate or cylindrical, 22-85 x 13-28 microns, single. Affected leaves turn yellow and die off.

Distribution.

The disease was recorded for the first time in 1988 in the western part of the former USSR in conditions of protected ground. It is recorded in Latvia, Russia (Saint Petersburg, Vologda, Novgorod, Moscow Regions), Byelorussia, and Ukraine, developing in the last country in conditions of open ground. The Powdery Mildew caused by L. taurica was found in Kazakhstan for the first time in 1957, and since 1966 in hothouses and in field conditions of Armenia and Krasnodar Territory where it is the most nocuous, resulting in decreases of tomato yield up to 50%.

Ecology.

Fungal mycelium and cleistocarpia are a source of the infection, staying on the affected plant residues and in the ground. Pathogens develop under a wide range of temperatures (18-28.C) and air humidity levels (60-90 %).

Economic significance.

The disease results in a decrease of assimilating surface of leaves reduction of tomato yield by 40-50%. Control measures include destruction of vegetation residues, alternation of cultures in crop rotation and treatment of plants by fungicides during vegetation.

Reference citations:

Braun U. 1995. The powdery mildews (Erysiphales) of Europe. Jena, Stuttgart, New York: G. Fischer. 338 p.
Gelyuta V.P., Ivanova G.P., Dorofeeva G.P., Belykh E.B., Koretskii P.M. 1994. Taxonomic position of the Powdery Mildew of tomatoes registered in the East Europe. Ukrainskii Botanicheskii zhurnal (Kiev) 51(4): 62. (In Russian)
Osnitskaya E.A. 1968. Diseases of vegetables. In: Polyakov I.Ya., Chumakov A.E., eds. Pests and diseases distribution on agricultural crops in RSFSR in 1967 and the forecast of their appearance in 1968. Moscow: Rosselkhozizdat. 120-125 p. (In Russian)
Papoyan F.A., Markosyan A.A., Bazhanova N.V., Avetisyan K.V. 1980. Testing of Benamil against the Powdery Mildew of tomatoes. In: Gvritishvili M.N., ed. Materials of the Transcaucasian coordination meeting on plant protection; 15-16 May, 1980; Tbilisi: Gruz NIIZR. 44-46 p. (In Russian)
Smetanina T.I., Filippov A.V. 1994. Progressing disease. Zashchita rastenii 7: 15. (In Russian)

© Khlopunova L.B.