Anil KumarNarwal, Sameer2016-11-152016-11-152009http://krishikosh.egranth.ac.in/handle/1/85682With a prime objective to investigate the role of environmental factors in epidemiology of Sclerotnia rot of Indian mustard and to diagnose the disease in field condition using spectral approach. Two mustard varieties viz. RH 30 and Varuna were sown on four dates of sowing last week of September, second week of October, last week of October and second week of November during the rabi season 2008-09. Disease incidence was recorded at weekly intervals after initiation of disease in all the treatments. The weather data of the corresponding periods were taken from the Agrimeterological. Observatory situated at Research farm of the Chaudhary Charan Singh Haryana Agricultural University, Hisar. The reflected radiance values in different IRs bands were measured with the help of Ground Fruth Radiometer (GTR) over crop surface in all the treatments under inoculated and uninoculated sites from 10.00 a.m. to 12.00 noon. The reflectance values in all form sands were also measured over Barium sulphate plate (100% reflection) for using as standard reflectance values over a surface. The per cent reflectance values were computed by taking the ratio of radiance value over a crop surface and standard radiance value over a Barium xii sulphate plate. These spectral reflectance values in IRs bands were used for computing spectral indices. Vegetation index, normalized difference vegetation index, perpendicular vegetation index and disease water stress indices on the same days of disease observations. The maximum disease incidence was recorded in first date of sowing and it decreased drastically with delay in sowings. The maximum incidence in first date of sowing was 27.6 and 25.6 per cent in mustard varieties RH-30 and Varuna, respectively. The weather parameters : maximum temperature, minimum temperature, morning relative humidity, evening relative humidity, sunshine hours and wind speed were correlated with disease incidence by pooling the data first for all the environments and then for both the varieties. The correlation coefficients ranged from 0.17 to 0.78 in both the cultivars. The disease incidence was directly associated with maximum temperature, morning and evening relative humidity whereas, incase of sowing environments, sunshine hours also played significant role in disease development. The regression model based on significant weather parameters, explained the variability in stem rot incidence upto 98 per cent, during different sowing environments. The reflectance values were higher in visible bands over healthy (uninoculated) crop in comparison to diseased (inoculated) crop. The reverse trend was observed in case of infra red reflectance over healthy and diseased crop surface. The vegetation indices values were higher in healthy crop as compared to diseased crop except disease water stress index-4. The correlation coefficients of vegetation indices varied from -0.73 to -0.74 in RH-30 and from -0.75 to -0.79 in Varuna. The regression model based on significant vegetation indices explained the variability in disease incidence upto 81 and 86 per cent in mustard varieties RH-30 and Varuna, respectively. The spectral approach can be used as diagnostic tool for stem rot incidence in mustard crop under field condition.enDiseases, Fungi, Mustard, Application methods, Sowing, Fruits, Crops, Biological phenomena, Planting, Relative humidityThesis