Epidemiological factors for development/progression of downy mildew (Peronospora alta) on blond psyllium (Plantago ovata)
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Authors
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B.S. RATHORE*
Abstract
Occurrence of downy mildew (Peronospora alta Fuckel) on blond psyllium (Plantago ovata Forsk.) is greatly influenced by various factors. For initial development of downy mildew sufficient inoculum (105 conidia/ml) couple with susceptible age of plant (70-80 days old plant), low temperature (15 and 20o C for 48 h) with high relative humidity (100% for 96 h) was found essential. Five-year field study was conducted to ascertain the role of different climatic factors for the development and progression of downy mildew in blond psyllium in order to develop a prediction models. Average time taken for the appearance of initial symptoms of downy mildew was 54 days after planting. Average apparent infection rate (r) was 0.0931 units/day while secondary spread and maximum infection was 57.0% and 59.6%, respectively. Progress of disease was gradual during initial phase but soon it was followed by a spread at compound interest rate until a plateau was reached. Temperature (max. and min.) was positively correlated but relative humidity was negatively correlated with the development of disease.
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