Diseases

Septoria piricola Desm. - White Spot of Leaves of Pear

Systematic position.

Division Deuteromycota, class Coelomycetes, order Sphaeropsidales, family Sphaeropsidaceae, genus Septoria.

Biological group.

This species is a biotroph.

Morphology and biology.

The fungus over-winters on fallen leaves as an anamorph. In spring the fungus produces many spores in old diseased leaves, which are released during rainy periods. Spores are carried by wind to young leaves, and the fungus penetrates into the plant. Lesions are gray-white, rounded or coalescent, distinctly separated by dark-brown limb from healthy tissue. At the end of summer the middle tissue of the lesion becomes thin; and pycnidia (teleomorph) develop there (150-200 microns in diameter), forming pycnospores. The latter are filiform, bent, with several septa, colorless or pale-olive, 48-60 microns long and 3.5 microns wide. The disease can continue development and spreading throughout the vegetative season.

Distribution.

The disease is widely distributed in all fruit-growing regions of the Russian Federation and other countries of the former USSR; but the disease is not harmful everywhere. Epiphytotic development of White Spot (infection reaches 50-100% one time in 2 years) is observed in the Belgorod Region, in central parts of the Krasnodar and Stavropol Territories, in Georgia. Moderate development of the disease (infection reaches 30-50% once in 3 years) occurs in Central-Chernozem, Central-Non-Chernozem, Northwest areas, in Volga region, northern part of Rostov Region, in Krasnodar and Stavropol Territories, in republics of Adygea, Karachay-Cherkessia, and also in the Black Sea area. Low development of the disease (infection reaches 10-30% once in 5 years) occurs in the Far East.

Ecology.

The fungus develops with high air humidity and at temperatures of 12 to 32.C. The optimum temperature for the fungus is 22-25.C. The optimum relative air humidity is 90% and more.

Economic significance.

Disease results in premature falling of leaves with white maculation, decreases in yield, worsening of host quality. Shoots that have no leaves have no time to prepare for winter. Methods of protection include the use of less susceptible plant cultivars, prophylactic measures directed at the decrease of infection sources, and chemical control.

Reference citations:

Ablakatova A.A. 1965. Mycoflora and the main fungal diseases of fruit plants in the south of the Far East. Moscow-Leningrad: Nauka. 146 p. (In Russian)
Byzova Z.M., Vasyagina M.P., Deeva N.G., Kalymbetov B.K., Pisareva N.F., Shvartsman, S.R. 1970. Flora of spore plants of Kazakhstan. Fungi imperfecti (Deuteromycetes). V. 5. Part 3. Alma-Ata: Nauka. 557 p. (In Russian)
Dgalagoniya K. 1969. White Spot of Pear. Sadovodstvo (Moscow), 9: 19. (In Russian)
Gabadze E.I. 1971. White Spot of Leaves of Pear (Septoria piricola Desm.) in Georgia and methods of its control. PhD Thesis. Tbilisi: Georgian institute of subtropical husbandry. 25 p. (In Russian)
Gabadze E.I. 1972. White Spot of Leaves of Pear and methods of its control. Works of institute of gardening, viniculture and wine-making. V. 21. Tbilisi: Ministry of Agriculture of Georgian SSR. 353-358 p. (In Russian)
James P.W., Hawksworth D.L. 1971. Ainsworth & Bisby.s dictionary of the fungi. 6th edition. Kew: CAB International. 663 p.
Kobakhidze D.M., Minkevich I.I., Khomyakov M.T., Khokhryakova T.M., Shibkova N.A. 1971. Diseases of fruit crops. Distribution of pest and diseases of agricultural crops of RSFSR in 1970 and forecast of their appearance in 1971. Moscow: Ministry of Agriculture of RSFSR, VIZR. 214-219 p. (In Russian)
Popov V.N. 1973. Gardening in middle strip of Russia. Moscow: Rosselykhozisdat. 288 p. (In Russian)
Smolyakova V.M. 2000. Fungal diseases of fruit trees in South Russia. Krasnodar: Vest.. 192 p. (In Russian)

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