Development of Image-Based Disease Scale of Phoma Blight of Potato Using k-Means Clustering

Disease identification of the plant at an early stage is a key to prevent the major diseases by minimal application of chemical pesticides. In West Bengal, phoma blight is now becoming an emerging dreaded disease of potato. Phoma blight is associated with development of numerous spots on leaflets, thereby reducing green photosynthetic area causing huge loss in potato tuber production. The disease rating scale for severity analysis has not been developed for this disease till now. In this paper, an image-based phoma blight disease rating scale has been developed using k-means clustering. The image of phoma blight  affecting potato leaflets has been captured using a DSLR camera by placing white paper background of leaflets. The percentage of affected areas has been calculated and an image-based phoma disease scale has been developed. The number of affected leaflet images has been given to several plant pathologists and they have assigned disease rating scores based on eye estimations. The score has been assigned for each leaflet considering the maximum number of same scores assigned by plant pathologists. The disease rating has also been assigned based on the actual affected area within each leaflet image using k-means clustering. The comparison has been performed between eye estimated scoring and k-means-based scoring to verify the scale. Finally, it has been observed that the new developed disease rating scale has given 87% accuracy in disease estimation with plant pathologists.