BIOLOGICAL-CONTROL OF ACACIA-LONGIFOLIA AND RELATED WEED SPECIES (FABACEAE) IN SOUTH-AFRICA

Two of the Australian acacias that are weeds in South Africa are also exploited commercially and the desirability of exotic Acacia is disputed. This conflict has created problems for the implementation of a biological control programme. After considerable debate, the issue was satisfactorily resolved by mainly considering insects that attack reproductive plant parts, thus suppressing the invasive potential of the weeds while not affecting the vegetative parts that are utilized. Four insect species have been released in South Africa: a bud-galling wasp, Trichilogaster acaiaelongifoliae Froggatt. which has had a major impact on the reproduction of its host plant. Acacia longifolia (Andr. ) Willd., and three seed-feeding weevils. Melanterius spp., which have been released on A. longifolia. Acacia melanoxylon R. Br. and the closely related Paraserianthes lophantha (Willd.) Nielsen (= Albizia lophantha (Willd.) Benth.) with as yet unfinalized results. In this review, the biological control of Acacia spp. and P. lophantha in South Africa is described. The rationale for the types of agents that are suitable. and the issues that have arisen through the conflict of interests. are presented.