Browsing by Author "Moran, Cliff"

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    Biological control of Acacia cyclops in South Africa : the role of an introduced seed-feeding weevil, Melanterius servulus (Coleoptera: Curculionidae), together with indigenous seed-sucking bugs and birds
    (2005) Impson, F A C; Hoffmann, John; Moran, Cliff
    Acacia cyclops A. Cunn ex G. Don, or rooikrans (Fabaceae), of Australian origin, is an invasive environmental weed in South Africa where it threatens the unique vegetation of the Cape Floral Kingdom. The invasiveness of the plant in South Africa is, in part, due to its high annual seed-yields, together with the suitable climatic and edaphic factors found here. This study investigated the role of a seed-feeding weevil, Melanterius servulus, which was first introduced into South Africa during 1991, as a biological control agent of A. cyclops seeds, together with the combined effects of indigenous seed-sucking bugs and birds. The weevils utilise filled green pods of A. cyclops for adult feeding, oviposition and larval development and completely destroy seeds during these activities. Examination of the reproductive phenology of A. cyclops showed that seeds are produced annually, during summer and that the presence of filled green pods on the plants coincides with the period of reproductive activity of the weevils. Melanterius servulus populations have established readily at all the original release sites, and within four years of release, damage levels to seeds commonly reached 90%. The weevils have dispersed at an average rate of approximately 2 km per year. Since becoming established in South Africa. the seeds of A. cyclops have been utilised by a variety of generalist vertebrate and invertebrate organisms. Indigenous polyphagous alydid bugs feed on the mature seeds, rendering a portion of the crop inviable when damage levels are high (more than five feeding-punctures per seed). Several bird species are attracted to and feed on the fleshy aril that surrounds theseeds of A. cyclops. Passage of the seeds through the gut of birds enhances germination rates. There is a synergetic relationship between alydids and birds because seeds with low levels of alydid feeding (one to four punctures per seed) germinated more readily after passage through birds than seeds that were not eaten by birds.
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    Climatic change, habitat modification and relative age of dung beetle taxa (Coleoptera: Scarabaeidae, Hydrophilidae, Histeridae, Staphylinidae) in the South-Western Cape
    (1990) Davis, Adrian Louis Victor; Moran, Cliff; Hoffmann, John
    1. Two study sites near Pretoria in the Transvaal were located in a summer rainfall climatic area, type 113d (Walter & Lieth 1964), on deep and in both open woodland and grassland. 2. Eleven study sites in the south-western Cape were distributed between two winter rainfall climatic areas, type IV in the Cape of Good Hope Peninsula and type III(IV)a (Walter & Lieth 1964) on the west coast. The west coast could be divided into two subregions, the coastal belt of deep calcareous sand and the Darling Hills comprising predominantly sandy soils with a higher clay fraction. Vegetation at the sites formed a gradient from low, dense pasture to taller sparser shrubland; The five pasture sites were distributed between all three subregions whereas the six shrubland sites were located only in the Cape of Good Hope Peninsula and on the west coastal belt. 3. Pitfall traps baited with cattle dung were used to sample dung beetle fauna over 24h periods once a week in the Transvaal, irrespective .of weather (three traps/site), and on three sunny occasions per month in the south-western Cape (ten traps/site) for one year. 4. A further 13 study sites used for back-up studies in the south-western Cape were concentrated into three localities, three in the Cape of Good Hope Peninsula, six on the west coastal plain and four-in the Darling Hills. These sites comprised different combinations of pasture (five sites) and shrubland (eight sites) habitats. Five traps at each site were baited on one 24h occasion each month over six months.
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    Neltumius arizonensis (Schaeffer) (Coleoptera: Bruchidae) as a biological control agent of mesquite (Prosopis spp., Mimosaceae) in South Africa
    (1996) Coetzer, Willem; Hoffmann, John; Moran, Cliff
    In the late nineteenth century, six North American mesquite taxa (Prosopis spp., Mimosaceae) were introduced into South Africa. They were to provide shade for livestock, and their pods were valued as a source of fodder. All Prosopis species in south Africa were recognized, as weeds in 1983. In 1987 a biological control programme using seed weevils (Coleoptera: Bruchidae) was launched against the two most invasive taxa, namely, P. glandulosa var. torreyana (L. Benson) M.C. Johnston and P. velutina Wooton. Algarobius prosopis (Leconte), the first biocontrol agent released, destroys large numbers of mesquite seeds annually, where livestock do not graze pods that are lying on the ground. Where pods are grazed, however, there is insufficient time for A. prosopis to inflict an adequate degree of seed damag'e before pods are eaten. For this reason another bruchid, Neltumius arizonensis (Schaeffer), which was reported to be capable of ovipositing on immature and mature tree-borne pods, was released in 1993. The establishment of N. arizonensis on mesquite at three sites in Western Cape Province was confirmed by monitoring N. arizonensis oviposition and emergence in the field. High levels of oviposition by N. arizonensis on tree-borne pods in June 1994 (39 and 29 'egg-seeds' at Onderplaas and Clanwilliam, respectively) were accompanied by high rates of trichogrammatid egg parasitism. Most pods had fallen to the ground by this time. The degree of egg parasitism was independent of N. arizonensis egg density. From December 1994 until June 1995, N. arizonensis egg densities were lower than those recorded in June 1994. The rate of field oviposition by N. arizonensis returned to high levels in August and September 1995, when 'tree pods' were again few in number. Neltumius arizonensis eggs were more abundant on 'tree pods' than on 'ground pods' in August and September 1995.