Biological Control of Mesquite Weeds in South Africa Using a Seed-Feeding Bruchid, Algarobius prosopis: Initial Levels of Interference by Native Parasitoids

A seed-feeding bruchid, Algarobius prosopis (LeConte), has been introduced into South Africa for biological control of alien mesquite taxa, Prosopis spp. (Fabaceae), that are troublesome weeds in the semi-deserts of the northwestern parts of the country. Six native Acacia species are common within the region where mesquite is most invasive in South Africa. The seeds of these acacias are the food source for at least 13 species of bruchids, which in turn serve as hosts for a complex of parasitoid species. Since the introduction of A. prosopis into South Africa, 9 of the parasitoid species normally associated with bruchids on the 6 sympatric Acacia species, and one parasitoid of unknown origin, have been reared from mesquite seed pods. However, the parasitoids were always scarce on mesquite and levels of parasitism were too low to have had an adverse affect on A. prosopis as a biocontrol agent