Rhamphicarpa fistulosa is a new parasitic weed of rain-fed rice in Africa. The weed is native to Africa, but was not a problem until rice farmers started to expand rice cultivation into the natural habitat of this species, which are seasonally flooded lowlands. The weed is a facultative parasite that grows much more vigorously once attached to the roots of its host. Through the extraction of nutrients, water and carbohydrates the parasite reduces the yielding ability of rice. At the start of this research, the parasite was relatively unknown to farmers and scarcely reported in literature. The study focussed on unravelling the ecology and biology of R. fistulosa, and the interaction between the parasite and rice. Germination of the weed seeds requires the combination of light and a water-saturated soil. In contrast to many other parasitic weeds, root exudates of the host plant did not trigger germination. A time lag of seven weeks between seed germination and attachment was observed. Soon after establishment of a connection with its host plant the parasite starts influencing its host, resulting in a modified biomass allocation and a reduced leaf photosynthetic rate. Eventually the parasite completely dominates its host. The implications of these findings for sustainable management are discussed. This research is part of the larger PARASITE-project, in which apart from the biology, management and economics of parasitic weeds in rice in Africa were investigated, as well as the institutional environment for national crop protection services.