Cape-ivy (Delairea odorata Lamaire) is an ornamental vine that has escaped into natural areas in many countries and become a serious pest. It is native to the eastern part of South Africa, and surveys there located several potential biological control agents for this weed. One of these is Parafreutreta regalis Munro, a tephritid fly that causes large galls to form on the stems of the vine. In a collaborative effort, we began to evaluate, in both California and South Africa, the host range of this fly. Between the two locations, we tested 93 plant species and 2 varieties of Cape-ivy to see if, after being exposed to four pairs of flies for a week, any galls would develop on them. No galls were formed on any of the test species, although an average of six galls developed on each of the Cape-ivy controls. We also tested to see whether P. regalis showed any preference for either of the two varieties of Cape-ivy. There was no significant difference between the numbers of galls forming on the stipulate or astipulate varieties. Our tests indicate that this fly is essentially monospecific. Earlier research had shown that P. regalis galls cause a significant reduction in the height and nongall biomass of Cape-ivy. A petition has been submitted to initiate the process of obtaining permission to release P. regalis in California to control the Cape-ivy infestations there.