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 came across quite a few hakea trees in the Suurbraak mountains and we needed a few days work to apply the agent effectively. The fungus will spread naturally, especially if there is a lot of rain following its application. Over a few years, fungus will slowly kill the trees."You will see how beautiful the fynbos will come out, once all the aliens have been cleared" says oom Twakkie (Goliath Highburg, Guality Controller for the Conservancy). We cant wait to start seeing the results!
See the following link for more information on biocontrol options.
Gordon, A.J. and Fourie, A., 2011. Biological control of Hakea sericea Schrad. & JC Wendl. and Hakea gibbosa (Sm.) Cav.(Proteaceae) in South Africa. African Entomology, 19(2), pp.303-314.
GVB Conservancy Staff