Epidemiology and Disease Forecasting

Abstract

Epidemiology of crucifier’s powdery mildews is influenced by numerous factors of host, and pathogen origin under the prevailing environmental, and physical factors of soil, nutrition, and cultivation practices. After landing of inoculum in the form of pathogens conidia/ ascospores, their germination, and formation of appressoria to cause infection is influenced by environmental factors like temperature (minimum, maximum, averages), relative humidity (morning, evening, averages), sunshine hours, and wind velocity along with critical host growth stages. Host factors like age of the leaf, and stem under the influence of ambient temperature determines the infection, and spread of disease under field conditions. Interaction of pathogen with host at right growth stage coinciding with congenial environmental conditions favours disease development at faster rate. Stem infection is maximum, if they are exposed to the inoculum for longer duration especially at maturity stage of the crop. Infection on younger plants and newly emerging leaves is rare. Disease development is at faster rate if host-pathogen interaction coincides with favourable crop growth stages, and crucial environmental variables. Late planting is associated with high disease intensity. Host resistance curbs the area under disease progress curve (AUDPC), less disease intensity, higher incubation, and latent periods, low infection rate, less number of powdery mildew colony with less number of conidiophores, and conidial production. Disease forecasting system has been developed using historical, and current data on maximum severity of disease, crop age at first appearance of the disease, and crop age at peak severity of disease for two susceptible cultivars sown at different location. Weather data have been analysed to develop disease forecasting models.