Have you ever heard of a fungus that helps control invasive alien plants? Meet Cylindrobasidium torrendii, a naturally occurring fungus that could revolutionise black wattle treatment. This tiny organism is helping manage areas of invasive species like Acacia mearnsii (black wattle). Black wattle is a fast-growing, aggressive plant that spreads rapidly and outcompetes indigenous vegetation. Black wattle disrupts ecosystems by consuming excess water and nutrients, displacing the indigenous flora.
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Recently, the Grootvadersbosch Conservancy had the privilege of hosting Dr Alan Wood from the Agricultural Research Council, an expert in plant pathogen behaviour and biocontrol development. Dr Wood presented his biocontrol solution as an alternative to herbicide to control black wattle on cut stumps. The Conservancy is working with Dr Wood to test this approach in real world conditions.  

​The Grootvadersbosch Conservancy has worked on the removal of Pereskia aculeata over the past few years and knows how problematic an alien invader it is. The conservancy used to burn off every stem of the plant which was quite an expensive process. The Grootvadersbosch Conservancy has been working with the Swellendam municipality to manage alien invasives and noticed an invasion in the centre of town. We urgently required an easier way of eradicating the pesky Pereskia, so we contacted Dr. Iain Paterson to aid us with some biocontrol. He posted the biocontrol to us where we could release it at two sites – the first site is at a Swellendam municipality near the mall and the second site is at the Buffeljags Dam.

Last week, some team members went to the mountains above Suurbraak to apply a biocontrol agent to invasive hakea trees. Silky hakea (Hakea sericea) is an evergreen tree with very prickly leaves. It invades mountain fynbos as well as coastal grassland. A native of Australian, it was once cultivated for dune cultivation and hedging. Hakea trees usually grow fast and produce a lot of seeds. They form large stands and seeds can be transported by the wind for long distances, and new infestation develop quickly in neighbouring valleys. 

There are large infestations in the coastal mountains of the Cape floral region in the Western Cape. Many infestations occur in remote or inaccessible areas and so invasions can become extensive before they are noticed. A further challenge is that fire increases the prevelance of the population. For remote mountainous areas, bio control is most effective. Regular follow up is also always essential to keep the aliens in check. 

​Biocontrol makes use of a plant's naturally occurring enemies to reduce the invasive impact of a species. There are many different bio control agents that can control hakea but we used an indigenous fungus that has successfully been used to control hakea. The biocontrol was applied to the adult trees by spraying it on to an exposed wound which was made with a simple, custom-made tool (a plank with exposed nails). 

We are combining our approach to alien clearing in the high mountain areas with the release of biocontrol agents. Biocontrol makes use of an invasive plant's naturally occurring enemies to reduce the invasive impact of the species. The approach reunites weeds with their naturally occuring enemies, thereby achieving more sustainable weed control. Biological control is best combined with other mechanisms (mechanical and chemical) to achieve a multi-pronged approach.

We are specifically concerned with the prevalence of silky hakea in the upper mountain areas. In October 2020, we received training on the applicability of different biological control on silky hakea. The training was completed by Dr Wood from the Agricultural Research Institute. We have now ordered the appropriate hakea fungus which will assist with control across the conservancy.​