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Epidemiology of Foliar Blights (Spot Blotch and Tan Spot) of Wheat in the Plains Bordering the Himalayas

March 2005 , Volume 95 , Number  3
Pages  248 - 256

E. Duveiller , Y. R. Kandel , R. C. Sharma , and S. M. Shrestha

First author: CIMMYT, South Asia Regional Office, P.O. Box 5186, Kathmandu, Nepal; and second, third, and fourth authors: Institute of Agriculture and Animal Science, Rampur, Chitwan, Nepal

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Accepted for publication 18 October 2004.

Helminthosporium leaf blight (HLB), a complex of spot blotch caused by Cochliobolus sativus and of tan spot caused by Pyrenophora tritici-repentis, is a major wheat disease in South Asia. This 2-year study elucidated HLB development and its impact on yield. Symptoms caused by C. sativus and P. tritici-repentis were first observed at the seedling and tillering stages, respectively. The number of airborne conidia and leaves infected by the two pathogens remained low for several weeks under lower temperatures, followed by a sharp rise as temperatures increased. The number of airborne conidia of C. sativus and incidence of infection by C. sativus were higher compared with P. tritici-repentis. The disease complex caused an average 30% reduction in yield, with greater losses under delayed seeding. Delayed seeding increased disease severity even in resistant genotypes and caused higher yield losses. ‘Milan/Shanghai-7’ was the most resistant among six genotypes evaluated. Despite higher disease severity, ‘BL 1473’ showed relatively lower yield losses, indicating its tolerance to foliar blight. The findings of this study bear implications for integrated foliar blight management in the warmer areas of South Asia by combining optimum seeding date, seed treatment and foliar spray of fungicides, and resistant wheat genotypes.

Additional keywords: Bipolaris sorokiniana , Drechslera tritici-repentis , Indo-Gangetic Plains , integrated crop management , host resistance , rice-wheat system , Triticum aestivum .

© 2005 The American Phytopathological Society