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A form of the South African plant, Asparagus asparagoides, has become a severe environmental weed in Australia, where it is known as bridal creeper. During surveys conducted in South Africa, information was gathered on the distribution, host range and phenology of the rust fungus, Puccinia myrsiphylli, to assess its suitability as a biological control agent for bridal creeper. The distribution of the rust encompasses all rainfall regions of South Africa. In the winter-rainfall region, the rust was first recorded on A. asparagoides in autumn and then increased in abundance until highest levels were reached in spring, just before the foliage senesced. A similar but less distinct phenology was recorded in the region where rainfall is not restricted to any particular season (aseasonal). The rust fungus was recorded in summer-rainfall regions, but sampling was not frequent enough there to determine its phenology. Strains of P. myrsiphylli were found on five other Asparagus species. Further research is required to determine whether these strains should be separated into different species. P. myrsiphylli was common on the widespread form of A. asparagoides (the form that occurs in Australia), but was never recorded in the field on a second form of A. asparagoides that is restricted to the south-western Cape, supporting the suggestion that the two forms may be different species. Furthermore, Aecidium schlechterianum, Aecidium myrsiphylli and Uredo myrsiphylli are newly listed as anamorphs of Puccinia myrsiphylli. |
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