This paper analyzes the different computing techniques, which are used in the agricultural field. Expert systems are very much prevailing in the farming sector. Fuzzy logic, one of the methods of expert systems, is used in many ways to help out the agricultural problems. This paper discusses the major problem of the farming sector that is Agricultural Diseases. Some reviews are given which shows the agricultural diseases affecting crop yield and also shows the importance of prediction and detection analysis for crops. By prediction systems, farmers get the idea of disease and apply the required measures. Fuzzy logic versatility is also reviewed here and how it is helpful in different ways in the agricultural field. This paper proposes the use of the fuzzy logic inference system or expert system for precision agriculture by making use of rule-based approach. This will help farmers to control and manage the diseases and increase crop productivity.