Spot blotch (barley)

Spot blotch is a disease of barley caused by Cochliobolus sativus. The disease is found everywhere that barley is grown, but only significant yield losses in warm, humid climates.^[1][2]

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Symptoms

Infections appear as dark, chocolate-colored blotches. The spots merge, eventually forming irregular dead patches on the leaves. Leaf spots may be surrounded by a zone of yellow leaf tissue of varying width. Spot may also appear on the leaf sheaths, necks and heads of the plant. Heavily infected leaves dry up completely, and infections on the flag leaf during kernel filling are the most serious.

Disease cycle

The fungus overwinters in barley straw and stubble, in the soil, or on the seed. Spores are produced on barley debris in the spring and are dispersed by wind and rain. Barley seedlings may become infected from incolum on the seed or in the soil.

Temperatures above 20C and moist humid conditions within the crop canopy favour spot blotch development. Conducive weather conditions may favour successive production of new spores and lesions leading to rapid disease development during the growing season.

Yield loss

The disease may be particularly damaging in the Upper Midwest of the United States. Yield losses of 10-30% may be occur when weather conditions are conducive to disease development.^[1]

Management

The disease is managed used resistant varieties, clean seed, seed treatments, foliar fungicide and rotation to non-cereal crops.

Research articles

Clark, R.V. (1979). "Yield losses in barley cultivars caused by spot blotch". CJPP 1: 113-117.

Clay, R.P.; C.W. Bergmann, M.S. Fuller (1997). "Isolation and characterization of an endopolygalacturonase from Cochliobolus sativus and a cytological study of fungal penetration of barley". Phytopathology 87: 1148-1159.

Duczek, L.J. (1997). "Infection of wheat and barley by Bipolaris sorokiniana during early growth stages and effects on leaf area". CJPP 19: 293-296.

Eng-Chong, P.; R.-L. Pelletier, H.R. Klinck (1985). "Seedling blight, spot blotch, and common root rot in Quebec and their effect on grain yield in barley". CJPP 7: 395-401.

Fetch, Jr., T.G.; B.J. Steffenson (1994). "Identification of Cochliobolus sativus isolates expressing differential virulence on two-row barley genotypes from North Dakota". CJPP 16: 202-206.

Fetch, Jr., T. G.; B.J. Steffenson (1999). "Rating scales for assessing infection responses of barley infected with Cochliobolus sativus". Plant Dis. 83: 213-217.

Johnston, H.W.; J.A. Macleod (1987). "Response of spring barley to fungicides, plant growth regulators, and supplemental nitrogen". CJPP 9: 255-259.

Kutcher, H.R.; K.L. Bailey, B.G. Rossnagel, W.G. Legge (1994). "Heritability of common root rot and spot blotch resistance in barley". CJPP 16: 287-294.

Martin, R.A.; J.B. Sanderson (1988). "Yield of barley in response to propiconazole". CJPP 10: 66-72.

Pringle, R.B. (1981). "Nonspecific adhesion of Bipolaris sorokiniana sporelings". CJPP 3: 9-11.

Stevenson, I.L. (1981). "Timing and nature of seed infection of barley by Cochiliobolus sativus". CJPP 3: 76-85.

Valjavec-Gratian, M.; B.J. Steffenson (1997). "Pathotypes of Cochliobolus sativus on barley in North Dakota". Plant Dis. 81: 1275-1278.

Valjavec-Gratian, M.; B.J. Steffenson (1997). "Genetics of virulence in Cochliobolus sativus and resistance in barley". Phytopathology 87: 1140-1143.

Zhong, S.; B.J. Steffenson (2001). "Virulence and molecular diversity in Cochliobolus sativus". Phytopathology 91: 469-476.

References

1. ^ ^{a b} Mathre, D.E. (1997). Compendium of barley diseases. American Phytopathological Society, 120 pp. 
2. ^ Martens, J.W.; W.L. Seaman, T.G. Atkinson (1984). Diseases of field crops in Canada. Canadian Phytopathological Society, 160 pp.