Bibliography: leaves 64-69. / 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.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:uct/oai:localhost:11427/9270 |
| Date | January 1996 |
| Creators | Coetzer, Willem |
| Contributors | Hoffmann, John, Moran, Cliff |
| Publisher | University of Cape Town, Faculty of Science, Department of Biological Sciences |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Master Thesis, Masters, MSc |
| Format | application/pdf |
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