Abstract: Protozoan parasites of the phylum Apicomplexa include some of the most important causative agents of human and animal diseases, in particular, malaria. The discovery that an organelle found inside parasites of this phylum probably stems from a plastid of plant origin has stimulated research on the effect of chemical herbicidal agents on Apicomplexa. Members of the triazine family and of the dinitroaniline family of herbicides have been found to be active against some Apicomplexa. The present invention extends the list of chemical herbicidal agents active against Apicomplexa to include classes of herbicides active as carotenoid synthesis inhibitory agents in plants and herbicidal agents effective against fatty acid synthesis in plants.