The annual worldwide yield losses due to pests are estimated to be billions of dollars.Integrated pest management(IPM) is one of the most important components of crop production in most agricultural areas of the world,and the effectiveness of crop protection depends on accurate and timely diagnosis of phytosanitary problems.Accurately identifying and treatment depends on the method which used in disease and insect pests diagnosis.Identifying plant diseases is usually difficult and requires a plant pathologist or well-trained technician to accurately describe the case.Moreover,quite a few diseases have similar symptoms making it difficult for non-experts to distinguish disease correctly.Another method of diagnosis depends on comparison of the concerned case with similar ones through one image or more of the symptoms and helps enormously in overcoming difficulties of non-experts.The old adage ’a picture is worth a thousand words’ is crucially relevant.Considering the user’s capability to deal and interact with the expert system easily and clearly,a webbased diagnostic expert-system shell based on production rules(i.e.,IF < effects > THEN < causes >) and frames with a color image database was developed and applied to corn disease diagnosis as a case study.The expert-system shell was made on a 32-bit multimedia desktop microcomputer.The knowledge base had frames,production rules and synonym words as the result of interview and arrangement.It was desired that 80% of total frames used visual color image data to explain the meaning of observations and conclusions.Visual color image displays with the phrases of questions and answers from the expert system,enables users to identify any disease,makes the right decision,and chooses the right treatment.This may increase their level of understanding of corn disease diagnosis.The expert system can be applied to diagnosis of other plant pests or diseases by easy changes to the knowledge base. The annual worldwide yield losses due to pests are estimated to be billions of dollars. Teprated pest management (IPM) is one of the most important components of crop production in most agricultural areas of the world, and the effectiveness of crop protection depends on accurate and timely diagnosis of phytosanitary problems.Accurately identifying and treatment depends on the method which used in disease and insect pests diagnosis.Identifying plant diseases is usually difficult and requires a plant pathologist or well-trained technician to accurately describe the case. Moreover, quite a few nnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnn old adage ’a picture is worth a thousand words’ is crucially relevant. Conscious of the user’s capability to deal and interact with the expert system easily and clearly, a webbased diagnostic expert-system shell based on production rules (ie, IF THEN ) and frames with a color image database was developed and applied to corn disease diagnosis as a case study. The expert-system shell was made on a 32-bit multimedia desktop microcomputer. The knowledge base was frames, production rules and synonym words as the result of interview and arrangement. It was desired that 80% of total frames used visual color image data to explain the meaning of observations and conclusions. Visual color image displays with the phrases of questions and answers from the expert system, enables users to identify any disease, makes the right decision, and chooses the right treatment. This may increase their level of understanding of corn disease diagnosis.The expert system can be applied to diagnosis of other plant pests or diseases by easy changes to the knowledge base.