Evaluation, over 22 years, of biological control of an invasive cactus, Opuntia stricta, in the Kruger National Park, South Africa. Annually, from 1992 - 2013, the numbers of O. stricta plants, cladodes and fruits were recorded, along permanent transects, at four sites with different invasion-histories and with high- and low-densities of the cactus. The abundance of two biological control agent species was also monitored: (i) the cochineal insect, Dactylopius opuntiae, and (ii) the cactus moth, cactoblastis, Cactoblastis cactorum.