Development of Disease Scoring System for Severity Analysis of Late Blight of Potato based on Image Processing Approach

The severity for late blight disease of potato is quantified based on standard disease grading scale mainly by measure with the eye, which is greatly influenced by subjective factors and results in obvious error using Henfling disease estimation scale. The plant pathologists generally graded the late blight disease severity based on eye estimation for percent infected area according to the disease grading scale of Henfling. The disease scoring system is primarily the eye estimation methods and scores are varied among different pathologists. In this paper, an attempt has been made to develop image processing-based disease estimation for late blight of potato. The late blight affected portions of leaflets, leaves and whole plants have been evaluated using image analysis system. The percentages of affected areas have been calculated and scores have been assigned based on proposed scale. The assigned scores have also been verified from several plant pathologists based on Henfling’s disease scale. The gap of disease intensity variation between pathologist’s evaluation and image processing system has been fine-tuned by modification of the scale and finally the accuracy of scores estimation based on proposed image analysis system is 85% and could be effectively exploited for late blight of potato disease estimation.