Ageratina adenophora (Spreng.) R.M.King & H.Rob. and Ageratina riparia (Regel) R.M.King & H.Rob. (Asteraceae: Eupatorieae), originally from Mexico, are invasive in many countries. These plants produce thousands of wind- and water-dispersed seeds which enable them to spread rapidly and invade stream banks and moist habitats in areas with high rainfall. Two biological control agents, a shoot-galling fly, Procecidochares utilis Stone (Diptera: Tephritidae), and a leaf-spot fungus, Passalora ageratinae Crous & A.R. Wood (Mycosphaerellales: Mycosphaerellaceae), were introduced against A. adenophora in South Africa in 1984 and 1987, respectively. Both established but their impact is considered insufficient. Exploratory trips to Mexico between 2007 and 2009 to search for additional agents on A. adenophora produced a gregarious leaf-feeding moth, Lophoceramica sp. (Lepidoptera: Noctuidae), a stem-boring moth, probably Eugnosta medioxima (Razowski) (Lepidoptera: Tortricidae), a leaf-mining beetle, Pentispa fairmairei (Chapuis) (Coleoptera: Chrysomelidae: Cassidinae), and a leaf-rust, Baeodromus eupatorii (Arthur) Arthur (Pucciniales: Pucciniosiraceae) all of which have been subjected to preliminary investigations. Following its success in Hawaii, the white smut fungus, Entyloma ageratinae R.W Barreto & H.C. Evans (Entylomatales: Entylomataceae), was introduced in 1989 to South Africa against A. riparia. Its impact has not been evaluated since its establishment in 1990 in South Africa. By 2009, however, A. riparia was rarely observed in the field and E. ageratinae was noted to be present over most of the range of the weed, providing circumstantial evidence that the weed has been brought under biological control by E. ageratinae in South Africa.