Abstract: Indian economy is based on agriculture and Indian farmer’s life is linked with farming. Crop in the India is very prone to various viral attacks. It is important to prevent such attack and give more accurate solution to the farmers. To detect disease, leafs are essential parts of crop. Image processing technique is used to detect the leaf disease more accurately since necked eyes observation cannot provide accurate solution and also every person cannot be perfect in finding leaf disease. It is done in five stages like image acquisition, image preprocessing, feature extraction, classification and result. In this paper, we have presented a survey on the existing methods of plant leaf disease detection. Keywords: Image processing, feature extraction, acquisition, segmentation.