Disease progression and yield loss in barley associated with net blotch, as influenced by fungicide seed treatment

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Abstract
Fungicide seed treatment significantly reduced the severity of net blotch of barley induced by Pyrenophora teres. Triadimenol and maneb treatments were more effective than etaconazole, Vitaflo 280 (carbathiin plus thiram), or Vitaflo 250 (carbathiin). Disease severity at growth stage 73 (Zadoks) was reduced on the penultimate leaf from maneb and triadimenol seed treatments. Apparent infection rate (r) did not effectively identify relative treatment efficacy or potential. Estimated time to 50% disease severity on the second to fourth leaf from the head, based on logit disease transformation, was delayed by 2.5 to 9.2 days with triadimenol treatment. Triadimenol and maneb treatments provided a 12.6% and 12.4% yield increase, respectively, which was in part directly related to control of net blotch. Significant correlations of yield and thousand kernel weight to percent net blotch on the penultimate, third, and fourth leaves were obtained. It was estimated that net blotch on Volla barley was responsible for a 15.2% yield loss and 6.7% reduction in thousand kernel weight. Estimations of relative treatment efficacy and of yield loss were more reliable when based on disease assessments of the fourth leaf from the head than from higher leaf positions.