Infection and yield loss induced by groundnut leaf spots were determined with benomyl during the 1989 and 1990 crop seasons under natural disease pressure in the field in Sierra Leone. Weather conditions in both years were highly favourable to leaf spot infection and development. In 1989 benomyl, applied at weekly intervals and at the rate of 0.15 kg a.i. ha−1for a total of 10 applications, effectively controlled leaf spots and increased both pod and haulm yields by 85%. An estimated potential pod yield loss of 46% was recorded, indicating the importance of the diseases as major constraints to groundnut production in Sierra Leone. In 1990, however, a higher level of leaf spots severity was observed causing extensive damage of the foliage. Benomyl, applied at bi‐weekly intervals and at the rate of 0.225 kg a.i. ha−1for a total of five applications failed to effectively control the diseases, increasing pod yield by only 27%.