We face critical challenges in educating growers on wood-canker diseases of grapevines. Unlike other major diseases that appear every year with obvious symptoms (e.g., powdery mildew of grape), wood-canker diseases are often go unnoticed, yet they have more certain and detrimental effects on the plants. Because of this lack of sensational symptom development within a short period, it is difficult for agricultural educators to convince the growers to take urgent action. Modes of delivering extension-related information are changing. Reduced extension education budgets and changes in growers’ expectations have led to fewer of the standard, face-to-face meetings between extension agents and growers, and instead, have shifted toward distance-learning style approaches. In order to address these issues, we have developed a new web-based pictorial diagnostic key tool for grapevine trunk diseases. This tool aids users to determine a target grapevine trunk disease using a series of pictorial keys from different tissues of grapevines (leaves, trunks, cluster, etc.). Once enough information is obtained, it will provide the user a list of recommendations for management. This tool covers not only trunk diseases, but also some bacterial diseases and abiotic disorders that are similar in symptom expressions. It is hosted attreeandvinetrunkdiseases.org, and the website is freely available.