Euphorbia heterophyllaLinn., commonly known as wild poinsettia, is widespread in the tropics. It occurs as a major weed in six tropical countries, an important weed in 22 tropical countries and is present in a further 37 countries. It causes serious loss of yield and quality in a wide range of crops as it competes successfully by growing rapidly and forming a dense canopy over the crop. Dormancy is an important factor in the persistence of seed reservoirs in the soil and American and Nigerian work show light and temperature are important factors in germination. Pre-emergence herbicides do not give effective control for the whole growing season and as the weed becomes larger it is more difficult to control with post-emergence herbicides. In general the phenoxy-type herbicides give effective control, the triazines, ureas and uracils are variable and the acetanilides and anilines are poor. Some herbicide mixtures will suppressE. heterophyllalong enough to allow the establishment of the crop and minimise yield reduction but the best control has recently been obtained using a sequence of herbicides throughout the growing season.