Diseases

Septoria secalis Prill.et Del. - Septoria Leaf Blotch of Rye

Classification.

Class Deuteromycetes, order Pycnidiales, family Sphaerioidaceae, genus Septoria

Biological group.

Hemibiotroph.

Morphology and biology.

Septoria leaf blotch (Septoria secalis) is a common disease of rye leaves and may attack species of Hordeum, Avena, Agrostis. Sexual stage is unknown. Septoria secalis attacks leaves mainly. Small spots are situated between leaf veins, elongate, yellow-brown, becoming pale; they may appear in autumn on seedling leaves. On adult plants the spots spread frequently over the most part of an infected leaf. Black, spherical or oval pycnidia appear on spots during plant development. The fungus overwinters in pycnidia on crop debris or as mycelia in living leaves infected in autumn. In spring the fungus spreads as pycnospores from plant debris. Pycnospores (conidia) are straight, baculiform or cylindrical, with 1 to 3, sometimes 4 septae, 24-50 x 2.5-3.5 mkm in size. Infection on plants is commonly associated with splashes of rain drops. After pycnidia being formed on spots of vegetating plants, the spores produced in pycnidia disperse to other leaves of the same or other plants by different ways, especially by rain drops.

Distribution.

Occurs in different countries of Europe, Asia, Africa, America, and Australia, where rye is cultivated. In Russia it appears in the entire region, where rye is cultivated.

Ecology.

Septoria is an important fungus in humid temperate climates. The disease develops when the weather is not very hot (optimal - 15 to 20o). Rains and moist, humid periods favor the disease infestation. Pycnidia production and infection occur repeatedly during these periods in spring and summer and continue until crop ripening.

Economic significance.

Severe disease attacks cause yield losses from 10-15 to 40% because of the early leaves drying. Control measures include crop rotation, ploughing of plant debris, fungicide treatment of plants.

Related reference.

Ainsworth G.C. (Ed.). 1971. Ainsworth and Bisby's Dictionary of the fungi. - 660 p.
Ishkova T.I., Berestetskaya L.I., Gasich E.L., Levitin M.M., Vlasov L.Yu. 2002. Diagnostics of the main fungus diseases of cereal crops. . St.Petersburg - 76 p. (in Russian).
Kovalenko S.N. 1984. Dynamics of rye septoriosis development. / Sovershenstvovanie tekhnologii vyrashchivaniya zernovykh kul.tur . Kiev . P. 63-66 (in Russian).
Kovalenko S.N., Skuratovska O.V. 1987. Distribution and harmfulness of winter rye septoriosis. / Visn. s-g. nauki. .- N6. . P. 77-80 (in Ukrainian).
Levitin M.M., Tyuterev S.L. 2003. Fungal diseases of cereals crops. / Zashchita i karantin rastenii - N11. . P. 76 (in Russian).

© Dmitriev A.P.

Photo Dmitriev A.P.