Influence of weather factors on severity of aerial blight of soybean
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RESEARCH ARTICLE
Influence of weather factors on severity of aerial blight of soybean K. Surbhi1 · K. P. Singh1 Received: 23 January 2019 / Revised: 25 March 2020 / Accepted: 30 April 2020 © Indian Phytopathological Society 2020
Abstract The investigations were taken up at Soybean Pathology block, Crop Research Center, GBPUA&T, Pantnagar during 2016 and 2017 Kharif season. The data from the two crop seasons revealed that the period from the month of September to October is most favourable time for the development of RAB of Soybean. The mean, maximum and minimum atmospheric temperatures, relative humidity and rainfall were found to be significantly negatively correlated with disease development during both the years. The correlation of wind speed and evapotranspiration with the disease index was significant and negative while sunshine hours exhibited a non-significant and positive correlation with disease index. The R2 values indicate that there was 65–70 percent association of weather factors with disease severity in 2016 while during 2017 the association of weather parameters with disease severity was around 41–61 percent. Keywords Rhizoctonia aerial blight · Soybean · Epidemiology · Temperature · Relative humidity · Rainfall · Correlation
Introduction Soybean [Glycine max (L.) Merill] is one of the oldest and most important Kharif oilseed crop grown throughout the world in tropical, sub tropical and temperate climates. The lower productivity of the crop can be attributed to the attack of various fungal and bacterial diseases like seed and seedling rots, bacterial pustules, bacterial leaf blight, aerial blight, anthracnose, charcoal rot, soybean yellow mosaic and soybean mosaic. Among various diseases affecting the crop, aerial blight caused by the fungus Rhizoctonia solani Kuhn (teleomorph: Thanatephorus cucumeris (Frank) Donk) which develop over the leaves and make the plant weak and unproductive, is the most destructive. The disease has been reported to cause about 80% losses in the crop yield. The importance of the disease has increased due to the increased soybean production and expansion of the crop to new regions (Hartman et al. 2011). The severity of aerial blight is greatly influenced by the prevailing environmental * K. Surbhi [email protected]
conditions. Different environmental factors viz., temperature, relative humidity, bright sunshine hours and rainfall play a crucial role in the initiation and development of plant disease over time. The occurrence of favorable environmental condition together with the susceptible growth stage of plant is essential for the development of disease. The mycelium of the aerial blight fungus starts growing in a warm and humid weather on the stem and leaves of the plant during flowering stage of the crop and spreads from plant to plant by means of aerial mycelia. Occurrence of rainfall during flowering stage of crop has been reported to encourage the high severity of the disease (Yang et al. 1990). As such, the study of the combination of weather factor
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