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Preliminary investigation of prickly acacia (Acacia nilotica) dieback
Prickly acacia (Acacia nilotica) is a weed of national significance (WONS) which significantly impacts on the grazing industry across northern Australia. A dieback phenomenon has been reported to occur in some locations where this woody weed exists. A key element of this research project was a field study conducted in July 2010, during which several locations between Julia Creek and Richmond in northern Queensland were visited to investigate and collect material from sites with prickly acacia infestations. Particular effort was made to locate sites where active dieback could be found, and to collect information and samples from sites where it had previously been active.
The field work phase of this study provided an opportunity to capture useful biological and anecdotal information about the dieback phenomenon. Although large-scale active dieback was not observed during the study, significant evidence was captured to provide an understanding of past historical events. Dieback in prickly acacia appears to be linked to climatic events, and may be influenced by site-specific factors such as soil type and drainage. It is also influenced by the activity of insect pests such as locusts, stem borers and twig girdlers. A range of fungi were isolated from affected plants. Approximately 150 isolates were made from field collected material, of which 70% belonged to the genus Botryosphaeria. Many of these fungi were found to be capable of killing seedlings under laboratory conditions, and some are also capable of causing significant infection and dieback symptoms under glasshouse conditions.
The most effective isolates were those of the genus Botryosphaeria. The study has therefore indicated significant potential for harnessing some of these fungal isolates as bioherbicides to induce dieback symptoms in healthy prickly acacia plants. Is has also provided a sound basis for ongoing studies on research questions associated with this disease model. These studies will seek a better understanding of the disease mechanism and will also conduct field trials using inoculation methods currently being used in the research of dieback in parkinsonia (Parkinsonia aculeata).
This page was last updated on 24/07/2017
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