The GEOPOTATO project develops a decision-support system (DSS) for farmers in Bangladesh for an improved control of late blight in potato. Late blight, caused by Phytophthora infestans, is a highly infectious and destructive fungal disease in Solanaceous crops, for example, potatoes and tomatoes. To demonstrate and analyze the performance of the DSS, 19 demonstration fields have been implemented comparing farmers’ practice (FP) and the GEOPOTATO practice, i.e. late blight control based on the DSS developed by GEOPOTATO. This report describes the results obtained in the demonstration fields implemented in Munshiganj, Rangpur and Dinajpur during the 2018-2019 potato growing season. In general, potato growth and production exhibited normal patterns in the demonstration fields. Yields increased with longer growing periods. Late blight pressure was low in the 2018-2019 season according stakeholders. Despite the low late blight pressure average yields obtained in the GEOPOTATO plots was 9% higher than in the FP plots: 40.8 t/ha vs. 36.9 t/ha. In Dinajpur, yields of GEOPOTATO plots were 19% higher than FP plots, and in Rangpur and Munshiganj 13% and 2% higher, respectively. Farmers in charge of the FP plots sprayed less than the farmers controlling late blight in the GEOPOTATO plots. Especially in Munshiganj, GEOPOTATO demo farmers sprayed more frequently than FP farmers. The cost-benefit analysis of the GEOPOTATO control strategy versus the FP strategy showed that higher gross returns, associated with the higher potato yields in Rangpur and Dinajpur, outweighed the higher costs of the fungicides used in the GEOPOTATO strategy. In Munshiganj, the 2% yield increase in the GEOPOTATO plots was not enough to compensate the higher costs of fungicides. On average, the GEOPOTATO service resulted in an average financial benefit of 173 Euro/ha.