Plants is the heart of an agriculture field and it’s become an important source of energy as well as financial income. The leaves of a plant provides the most important information or data which provides us to know which type of plant it is and which type of disease is infected on that leaf. The plants have to be monitored all the time in order to detect the first symptoms of a disease before it is spread to the whole crop. Professional agriculture engineers may not be available to continuously monitor a crop. Remote monitoring through machine vision can offer an alternative option. After analyzing these different techniques as well as different algorithms, and identifying their limitations, we conclude with several promising directions for future research.