Long-term population studies and the development of an integrated management programme for control of Opuntia stricta in Kruger National Park, South Africa.
A phycitid moth, Cactoblastis cactorum, was released in Kruger National Park (KNP), South Africa, during 1988 in an attempt to control O. stricta biologically. Population counts of the biological control agent and of the weed over a 5-year period showed that, even though C. cactorum did not provide complete control of O. stricta in KNP, the moderate levels of larval damage stunted the growth of the weed and considerably extended the time that the young plants took to reach sexual maturity. Comparisons of modelled (i.e. with no C. cactorum) and actual populations of O. stricta showed that C. cactorum is making a substantial contribution to the control of O. stricta in residual infestations of the weed that have been treated with herbicides. The need for long-term evaluation studies in biological weed control is demonstrated by the development of an integrated management programme for the effective control of O. stricta.