Abstract In Burkina Faso, the leaf beetle Aphthona whitfieldi is the main insect pest of the biofuel plant Jatropha curcas. The beetle affects plant growth and seed yield, but the impact on yield has never been properly quantified. This study was conducted on-station and on-farm in the district of Léo, southern Burkina Faso, in 2015. It aimed at evaluating the yield losses that A. whitfieldi inflicts to J. curcas. The first experiment used 25 caged trees in their first year of fruit production, on which various amounts of beetles were released. When 200 beetles were released, the defoliation level reached 55% and caused 61% of yield loss. Releases of 400 or more beetles caused a defoliation level of at least 74% and seed losses of 98%. On-farm observations were made on attack levels and seed yields in three different types of plantations, i.e. pure plantations, plantations intercropped with food crops and hedges. These observations showed that defoliation levels over 50% were common in the three types of plantations, resulting in very low yields. This study shows the importance of beetle damage in the cultivation of J. curcas. This is likely one of the reasons for the very low yields, which, among other causes, led to the abandonment of J. curcas plantations in the region.