Role of temperature, relative humidity and rainfall in the development of French bean rust ( Uromyces appendiculatus)

Abstract

In plant disease development, temperature, relative humidity and rainfall are critical factors. To determine how specific environmental variables affect French bean rust, we determined the effect of these variables on disease development. Higher relative humidity (> 85%), moderate temperature (20–25 °C) and 18–24 h leaf wetness were found optimum for disease development. Effect of different meteorological factors on disease progress was studied under natural epiphytotic conditions and found that the disease was initiated in the second week of August and reached at peak in mid September. Multiple correlation coefficients between disease severity and these environmental factors suggested that 92.36% rust severity was due to mean temperature, average relative humidity and cumulative rainfall while rest of the variation may be attributed to the factors not included in the investigations. The multiple linear regression equation was fitted to the data and the equation arrived for all the weather parameters was, Y = − 52.4852 + 1.2535 X₁ + 0.8008 X₂ − 0.2862 X₃ + 0.4622 X₄ − 0.7755 X₅ + 0.2428 X₆. With the step, down procedure, three variable i.e., maximum temperature (X₁), cumulative rainfall (X₅) and wind speed (X₆) were eliminated and final equation fitted to the data is Y = − 37.4111 + 1.0622 X₂ + 0.5299 X₃ − 0.2868 X₄.