In this survey, we proposed computer aided with open source platform detection system for the leaf spot detection on cotton crop. This system plays very important role to improve outcomes in farming because it is important sector in India. Lot of peoples are depends on the cotton crop. There are many diseases on cotton crop. Due to this disease there is chance of the decrease productivity of the crop. Soour aim is to develop leaf spot detection system by using artificial neural network. Early detection of this disease can helpful for the farmer to take preventive action.