Controlling alien
invasive plant species
In our part of the Southern Karoo, we fight three exotic noxious weeds that are the biggest threat to the biodiversity in our area.
Jointed cactus
(opuntia-aurantiaca)
This is South Africa’s most costly exotic noxious weed and is a low growing, inconspicuous weed that slowly takes over grazing and renders whole areas impassable. The cactus is jointed in form with a barbus thorn that gets imbedded in the skin of passing victims, then falls out or is brushed off in the thick bush at a later stage, and then takes root where it falls. The State used to supply poison to fight this weed, but this is no longer available and needs to be funded by the land owner. Jointed cactus is South American in origin, and the anecdotal history of its entry into South Africa is that it arrived as an ornamental plant with a nun in the Fort Baufort area – it was apparently kept in a bottle for 18 months before being thrown out – and from there it has spread throughout most of South Africa. Jointed cactus is controlled by spraying it with Monosodium Mathenearsonate, commonly known as MSMA – an organic arsenical herbicide. At Royal Karoo the jointed cactus problem is taken seriously and resources are committed whenever time allows. Once an area is sprayed, we return 6 to 18 months later to make sure all stragglers have been eliminated.
Rope cactus
(cylindropuntia imbricate)
A plant that originated in Mexico and Texas and was introduced into South African via Australia in 1970. It is a tall growing bush, about 2.5 metres in height and quickly takes over large areas where it has been allowed to take root. The plant is spread by plant sections or segments of fruit which take root easily in our arid conditions. Fighting rope cactus is easier due to its tall growing nature, and is easily killed using Monosodium Methanearsonate or MSMA. At Royal Karoo we are well on our way to complete control of Rope cactus with only a few populations left to spray.
Torcia cactus
(Soehrensia Spachiana)
This plant is a native of South America and was introduced into South Africa in the early 1900’s, predominantly as an ornamental plant that has taken root and been allowed to spread extensively throughout South Africa. This cactus spreads easily along waterways and drainage lines as sections are broken off and transported by the water. Control of torch cactus is more difficult with no registered products, but spraying plants a year apart has proved to be successful at Royal Karoo, using Monosodium Menthanearsonate, or MSMA together with an adhesive.