Patterns of Aspergillus niger var. phoenicis (Corda) Al-Musallam infection in Namibian populations of Welwitschia mirabilis Hook.f.

The fungus, Aspergillus niger var. phoenicis effects the seeds of the Namibian endemic plant, Welwitschia mirabilis. In recent years, the increased spread of this fungus has raised concerns regarding the survival of this unique plant because of its perceived detrimental effect on seed germination and recruitment. Field studies conducted in different geographic areas of Namibia, namely at the Kuiseb River, Welwitschia Plains, Brandberg, Springbukwasser, Petrified Forest and Kaokoveld, in June/July 1998, showed clear regional patterns in the level of fungal infection. Fungal infection was significantly higher in the Brandberg area and lower at Welwitschia Plains. Autocorrelation spatial analyses suggest that the occurrence of the fungal disease is clustered. This supports previous evidence that Probergrothius sexpunctatis (Heteroptera) is an important insect vector in disease transmission. The data provides a baseline against which to monitor changes in the fungal infection in future years. (C) 2000 Academic Press.