Biological control of Australian myrtle, Leptospermum laevigatum (J. Gaertn.) F. Muell. (Myrtaceae), in South Africa

Leptospermum laevigatum (J. Gaertn.) F. Muell., an Australian shrub or smal l tree, is one of several woody plants introduced into South Africa in the early 1800s for sand dune stabilization. The plant has since become a major environmental weed, particularly in the unique and endangered fynbos veget ation of the Western Cape Province. In certain situations, L. laevigatum is rapidly replacing Acacia saligna (Labill.) Wendl., another Australian weed that is being brought under biological control. The biological control pro gramme against L. laevigatum has been opportunistic and has so far involved the release of a single agent. Since 1996, a leaf-mining moth, Parectopa t halassias Meyrick (Gracillariidae) has been released throughout the range o f L. laevigatum in South Africa. The moth has become established at virtual ly all of the release sites and has dispersed up to 2 km from some of these . An unidentified gall midge (Cecidomyiidae), which was discovered at a few localities in the Western Cape between 1994 and 1996, may also contribute to biological control. Post-release evaluations on the impact of both natur al enemies are scheduled. Although this programme is still in its infancy, prospects for biological control of L. laevigatum seem promising.