Diseases

Cercospora oryzae Miyake (teleomorpha Sphaerulina oryzina Hara) - Cercospora Leaf Spot, Narrow Brown Leaf Spot

Systematic position.

Division Eumycota, subdivision Deuteromycotina, class Hyphomycetes, order Hyphomycetales, family Dematiaceae, genus Cercospora.

Biological group.

Hemibiotrophic parasites.

Morphology and biology.

Lesions short, linear, brown to dark brown, 2-10 x 1-1.5 mm, located parallel to midrib or veins of leaves. The fungus shows similar symptoms on sheaths, pedicles, and glumes. The disease appears usually after booting or during later stages of plant growth. Conidiophores emerge through the stomata, being solitary or locating in fascicles by 2-4 ones, being pale to medium brown, sometimes dark brown, aseptate or 1-2-septate, unbranched or branched with 1-2 geniculations, with 1-5 thickened scars, 30-70 x 3.5-4 mkm. Conidia are hyaline, cylindrical to obclavate, straight or slightly curved, 3-10 (mostly 1-4) septate, obconic at base having thick dark scar, obtuse at apex, 12-60 x 2.5-3mkm. Fungal mycelia overwinter on infected residues. In spring the fungus produces conidiophores and conidia. During vegetation the infection is carried out by conidia. The incubation period is about 3 weeks.

Distribution.

Everywhere in zones of rice cultivation.

Ecology.

Development of the disease is possible in a range of temperatures 6 to 35.C, optimum temperature is 25-28.C. The disease may develop at deficiency of moisture, at lack of N and K.

Economic significance.

At the disease epiphytotic development the losses may reach 40%. Data on the disease severity in Russia are absent in the literature that testifies to an inessential influence of the Phyllosticta Leaf Spot on rice yield in this country. Protective actions. Careful removing of residues, autumn treatment of soil, treatment of seeds before sowing by fungicides, cultivation of resistant cultivars.

Related references:

Ainsworth G.C. 1971. Ainsworth & Bisby's Dictionary of the fungi. Sixth edition. Kew, Surrey: Commonwealth Mycological Institute. 663 p.
Dorofeeva L.L., Kodyakov A.A., Kratenko V.P., Lebedev M.B., Motovilin A.A. & Tikhonova N.A. 1992. Fungal diseases of rice. Tashkent: FAN. 94 p. (in Russian).
Egorova L.N. 1991. Cercospora and related genera of Hyphomycetes of the Far East. Mikologiya i Fitopatologiya 25(4): 288-294. (in Russian).
Sutton B.C. & Shahjahan A.K.M. 1982. A comparison of the symptoms and causal agents of narrow brown leaf spot and white leaf streak of rice. Nowa Hedwigia 35(2/3): 197-205.

© Gasich E.L.