Climate-Related Differences in the Efficacy of the Australian Gall Wasp (Hymenoptera: Pteromalidae) Released for the Control of Acacia longifolia in South Africa

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Abstract
The gall wasp Trichilogaster acaciaelongifoliae Froggatt (Pteromalidae) was released at 136 sites throughout the distribution area of the weed Acacia longifolia (Andrews) Willdenow in the Cape Province and Natal, South Africa. Each site was monitored annually to determine whether the wasp would establish and to determine its effectiveness where it had established. T. acaciaelongifoliae did establish throughout the range of A. longifolia. In the cooler coastal regions of the southwestern Cape and southern Cape, the wasp established well and levels of infestation were consistently high. However, in the hotter inland valleys and west coast of the southwestern Cape Province, and in Natal, establishment was poor and infestation levels were consistently low. In Australia, A. longifolia occurs naturally along the coastal regions of southern Queensland, New South Wales, Victoria, and eastern South Australia. However, the T. acaciaelongifoliae individuals released in South Africa originate only from the coastal regions of New South Wales and Victoria, and Tasmania. Climatically, these areas correspond most closely to the regions in which the wasp is most successful in South Africa. The method whereby the insects were released in South Africa, and the methods for evaluating the degree of establishment and subsequent infestation levels at each release site, are described.