Councllor Ben Rheeder advises that Kouga Municipality, Frank Tamboer, promised that four bush-clearing teams will start clearing POS’s and overgrown private plots in St Francis Bay, Cape St Francis and Paradise Beach from Monday 15 February. Teams will start in St Francis Bay, then Cape St Francis and then Paradise Beach.
Rooikrans (Acacia cyclops) is a tree originally from Australia brought to Cape Town as an ornamental tree in the 1800’s and later used for dune stabilisation on the Cape Flats. It is a tree reaching 5m with woody stems (Figure 2), tapered narrow supple green 1 x 8cm leaves with a rounded point and three mid-veins, 1cm round yellow flowers (Figure 3) and 10cm long curved seed pods. The seeds are dispersed by birds (long distance) and ants (short distance) and are able to lie dormant in sand for 40 years.
The detrimental effects on nature are that it uses massive amounts of water compared to fynbos, creates a canopy impenetrable by sunlight over natural vegetation leading to the death of the natural vegetation (Figure 4), stabilises dunes, out-competes natural vegetation, contributes to a loss in biodiversity, makes nitrates available to the soil which our natural vegetation cannot tolerate and creates a serious fire hazard due to a massive fuel load and highly flammable oils. Contrary to popular belief is that due to the highly flammable oils found in living trees, a dead Rooikrans is less flammable than a living Rooikrans!
Rooikrans has been placed by CARA (The Conservation of Agricultural Resources Act) in Category 2 which simply put means that it may only be grown under controlled conditions. The methods through which it can be controlled are mechanical, chemical or biological. For mechanical control the tree may be felled or seedlings under 65cm may be pulled by hand. For felling, the stumps do not need an herbicide application as it is very seldom a resprouter. Chemical control may be utilised in the form of applying herbicide for foliar spraying or basal stump application. Biological agents are also currently playing a role. The seed weevil
Port Jackson willow (Acacia saligna) is a very adaptable and fast growing species, native to Western Australia. It has become one of the most widespread and destructive invasive species in the fynbos region. It is a very difficult species to manage as it is able to resprout from its roots after being cut down and creates massive, long-lived seed banks. The difficulty and cost of eradicating this fast spreading species led to it being targeted for biological control measures.
The gall forming rust fungus Uromycladium tepperianum has proven very successful at controlling reproduction and seed set in Port Jackson. Through wind dispersal this rust fungus is now found wherever Port Jackson is growing in fynbos and it has been found to lower population densities by at least 80% in the absence of fire. The rust fungus reduces the flowering and seed set on Port Jackson and often ends up killing the plants after a few years. It is thought that the rust fungus does not kill the plants by itself but death is rather the result of the high number of galls formed on the plant together with environmental stress such as drought.
These two biological control agents have proven very useful in the battle to control alien invasive species in the fynbos.