Diseases

Phoma betae Frank - Zonate Leaf Spot, or Phomosis of Beet.

Taxonomic position.

Division Eumycota, subdivision Deuteromycotina, class Coelomusetes, order Sphaeropsidales, family Sphaerioidaceae, genus Phoma.

Synonyms.

Phoma sphaerocarpa Rostr., Phyllosticta betae Oud., P. tabifica Prill.

Biological group.

Facultative saprotroph.

Morphology and biology.

The disease appears in the second half of vegetation period. Yellow and light-brown rounded (3-5 mm in diameter) necrotic spots appear on the lower leaves of beet. They expand gradually, frequently merging in larger formations, and necrotic tissue drops out of middle of the spots. Leaves dry out. Later fine black dots (pycnidia) are formed on the spots. Necroses appear on leaf petioles, on stalk parent plants, and on flower-bearing shoots, having the form of brown longitudinal spot-bearing pycnidia. The fungus also affects petals of perianth, and infects seed glomes. Mycelium is colorless, gray or dark gray, strongly ramified, 3-5 microns in width. Pycnidia are entirely immersed in epidermis at first, projecting later, spheroid-flattened, light to dark brown, 100-400 microns in diameter, having a pore in the top part; the pore is 20-30 microns in diameter. Conydia are unicellular, colorless, ovoid, 5-7 x 3.5-4 microns in size. In damp weather they are squeezed out of pycnidia as colorless or pinkish threads as wide as the pore. The disease develops more often on beet leaves weakened by other fungi or suffering from physiological diseases. Phomosis causes also infection of shoots by Pythium debarianum, Phoma lingam and other diseases.

Ecology.

The agent winters on vegetation residues in the upper ground layer at depth of 5-15 cm, also in seeds and roots as pycnidia and mycelium. The fungus develops well at relative air humidity 60-70%, temperature 15-30.S (optimum is 25.C), and soil acidity pH 7.

Distribution.

The disease is found in all beet-growing areas.

Economic significance.

At high severity the productivity of roots is reduced by 29%; seed germinations by 39.7%; sugariness by 1.17-1.58%; weight of seeds by 11.7-19.1%. Protective actions include removal of yield remains from fields, subsequent deep autumn plowing; seed dressing; maintenance of crop rotation; optimum terms of planting; treatments of plantation by fungicides; use of resistant varieties.

Reference citations:

Ainsworth G.C., ed. 1971. Ainsworth and Bisby's Dictionary of fungi. 6 ed. Kew, Surrey: CAB Intern.: 663 p.
Al.khovskaya T.F. 1969. Fungal diseases of sugar beet in Chu River valley of Kirghizia. PhD Thesis. Tashkent: ANUzbSSR, 19 p. (in Russian).
Amanzholov A.A. 1980. Fungal diseases of seed sugar beet in Kazakhstan and their control. PhD Thesis, Alma-Ata: KazakhSKHI, 18 p. (in Russian).
Amanzholov A.A., Agataev M. 1985. Characteristics of control of cercosporosis and phomosis on parent sugar beet in Kazakh SSR. In: Zubenko V.F., ed. Effective measures of sugar beet protection from diseases at industrial technology of its cultivation. Kiev: VNIS, p.130-132. (in Russian).
Gelimbatovskaya R.V., Broyakovskaya K.N. 1985.The main sources of disease agents on parent sugar beet crops at their non-landing cultivation in the south of Ukraine. In: Zubenko V.F., ed. Effective measures of sugar beet protection from diseases at industrial technology of its cultivation. Kiev: VNIS, p.122-127. (in Russian).
Popova I.V. 1968. Diseases of sugar beet. In: Polyakov, I.Ya., ed. Distribution of pests and diseases of grown crops in the USSR in 1967 and the forecast of their appearance in 1968. Moscow: Rossel.khozizdat, p. 94-96 (in Russian)..
Popova I.V. 1969. Diseases of sugar beet. In: Polyakov I.Ya., Chumakov A.E., eds. Distribution of pests and diseases in agricultural crops in the RSFSR in 1968 and the forecast of their appearance in 1969. Leningrad: VIZR. p. 116-119 (in Russian).
Popova I.V. 1971. Diseases of sugar beet. In: Polyakov I.Ya., Minkevich I.I., eds. Distribution of pests and diseases in agricultural crops in the RSFSR in 1970 and the forecast of their appearance in 1971. Moscow: VIZR, p.148-154 (in Russian).
Popova I.V. 1973. Diseases of sugar beet. In: Polyakov I.Ya., Minkevich I.I., eds. Distribution of pests and diseases in agricultural crops in the RSFSR in 1972 and the forecast of their appearance in 1973. Moscow: VIZR, p.112-116 (in Russian).
Popova I.V., Zlotnikov M.D. 1970. Diseases of sugar beet. In: Polyakov I.Ya., Minkevich I.I., eds. Distribution of pests and diseases in agricultural crops in the RSFSR in 1969 and the forecast of their appearance in 1970. Moscow: VIZR, p.205-212 (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).
Pozhar Z.A., Dzhanuzakov A. 1969. Cercosporosis and other diseases of sugar beet. In: Polyakov I.Ya., Chumakov A.E., eds. Distribution of pests and diseases of grown crops in the USSR in 1966 (Proc. VIZR, V. 34). Leningrad: VIZR, p. 203-208 (in Russian).
Pozhar Z.A., Tishchenko E.I. 1968. Diseases of sugar beet. In: Chumakov A.E., Minkevich I.I., eds. Distribution of diseases of grown crops in the USSR in 1967. Leningrad: VIZR, p. 29-35 (in Russian).
Valovikova G.D. 1985. Distribution of diseases and protection sugar beet parent crops at their non-landing cultivation in Krasnodar Territory. In: Zubenko V.F., ed. Effective measures of sugar beet protection from diseases at industrial technology of its cultivation. Kiev: VNIS, p.127-130 (in Russian).

© Khlopunova L.B.