Spatial spread gradient model and short-range expansion of grape downy mildew
This study investigated the spatial dynamics of grape downy mildew epidemics by analyzing the spread gradient and spatial distribution of grape downy mildew in a field plot in Shenyang from 2018 to 2019.The direct and multi-directional spreading gradient models of the disease were constructed using the curve equation fitting program in OriginPro 2019 software.The obtained model parameters can describe the spatial dynamics of the disease epidemic in different directions and dimensions.The distance and rate of disease spread were deduced using the exponential model.The results showed that the initial grape downy mildew-infected plants were primarily located near the center of the pathogen source,and the disease index of a single plant was low.However,the disease index of the surrounding plants increased markedly,demonstrating a bell-shaped distribution in horizontal spread.The disease spreaded directly from the center.The exponential model was determined to be the optimal model for the direct spread gradient of the disease in the field.The spread of the disease in the direction parallel,or perpendicular,to the ridge showed a skewed normal distribution,with the disease center shifted to the north and east of the field.This shift was attributed to differences in wind direction and speed.The disease multidirectional spread gradient was bell-shaped and asymmetrically distributed,and the Gaussian surface model was found to be the most suitable for describing the multidirectional spread gradient in the field.The exponential model accurately predicted the maximum distance in the east,west,south,and north directions to be between 19.3-41.1 meters,and the average daily spread rate to be between 0.18-0.45 meters per day.
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