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Ecology and Epidemiology

Incidence of Bipolaris and Fusarium on Subcrown Internodes of Spring Barley and Wheat Grown in Continuous Conservation Tillage. Carol E. Windels, Associate professor of plant pathology, Northwest Experiment Station, University of Minnesota, Crookston 56716; John V. Wiersma, Associate professor of agronomy, Northwest Experiment Station, University of Minnesota, Crookston 56716. Phytopathology 82:699-705. Accepted for publication 25 March 1992. Copyright 1992 The American Phytopathological Society. DOI: 10.1094/Phyto-82-699.

Two cultivars each of barley and wheat were planted in three tillage systems (minimum till, chisel plow, and moldboard plow). Subcrown internodes were sampled twice each season (near heading and in the hard-dough to ripening stages) for common root rot and infection by Bipolaris sorokiniana and Fusarium spp. (F. acuminatum, F. avenaceum, F. culmorum, F. graminearum) in the fourth and fifth years of continuous cultivation. No significant interactions occurred between tillage and cultivar for the variables measured. Tillage had no effect on root rot indices (0100 scale) of barley or wheat sampled at the hard-dough and ripening stages. Indices averaged 57 for barley and 47 for wheat across years. B. sorokiniana was isolated more frequently from subcrown internodes of barley (average = 66%) or wheat (average = 58%) in moldboard plow plots than from subcrown internodes of barley (average = 47%) or wheat (average = 40%) in minimum-tillage plots. Fusarium spp. were isolated more frequently from subcrown internodes of barley (average = 18%) or wheat (average = 22%) in minimum-tillage plots than from subcrown internodes of barley (average = 7%) or wheat (average = 11%) in moldboard plow plots. Isolation of F. graminearum was 10, 5, and 3% from subcrown internodes of barley and 18, 21, and 11% from subcrown internodes of wheat in minimum-tillage, chisel plow, and moldboard plow plots, respectively. Isolation of F. avenaceum was 5, 0.6, and 0.9% from subcrown internodes of barley and 6, 0.9, and 0.3% from subcrown internodes of wheat in minimum-tillage, chisel plow, and moldboard plow plots, respectively. Tillage treatment did not affect isolation of F. acuminatum or F. culmorum.

Additional keywords: Cochliobolus sativus, Gibberella zeae, Hordeum vulgare, Triticum aestivum.