Late blight, caused by Phytophthora infestans, continues to be one of the major threats to potato (Solanum tuberosum) production, especially in developing countries. Resistant cultivars and fungicides are the main tactics used to fight the disease, however, it was not clear which competencies resource-poor farmers needed to best control this disease. A competence is a "standardized requirement for an individual to properly perform a specific job, including a combination of knowledge, skills and behavior". This study describes how competence analysis was used to develop a training guide for extension workers in Ecuador. A group of farmers, extension workers and plant pathologists identified five competencies needed to manage late blight efficiently: i) capable of recognizing the symptoms of disease and know which organism causes it; ii) know how this organism lives; iii) identify the characteristics and benefits of using resistant potato cultivars; iv) use fungicides appropriately; and v) by periodically visiting the potato field, be able to select practices that control late blight efficiently. Mental abilities, physical skills, attitudes and information specific for each competence were identified and from those, learning objectives were defined. Based on the objectives, the contents for each training session were defined, after which learning strategies and evaluation questions were developed. A Spanish version of the training guide was developed and iteratively tested and improved in three farmer field schools in the central highlands of Ecuador. The guide was then published in Spanish, and subsequently translated to and published in Ecuadorian Quechua and English.