| Information sheets | | | Elsenburg infopaks | | | Trees: 5 |
Prosopis
Afrikaans | Xhosa
 Click to enlarge! |
To the traveller in the Great Karoo and in parts of the Northern Cape, the
prosopis tree or "muskietboom" is a welcome sight. The tree with its characteristic long pods can reach a height of 25 m or more, and provides shade for man and beast.
The nature of the tree and its extraordinary ability to adapt in extreme weather conditions, together with the high protein content of its pods that can be fed to animals in times of drought, made it the commended tree until the fifties. |
 Click to enlarge! |
The tree originated in the dry southwesterly parts of the USA, Mexico and Chili, from where it was imported to South Africa, where it became established. Of the various Prosopis species and their hybrids, there are especially two that flourish in South African conditions, namely heuning prosopis and fluweel prosopis. The small yellow flowers are borne in finger-like clusters.
The colour of the pods varies from yellow to yellowish-brown to purple, and the pods are straight or slightly curved. As the pods mature, they become woody, but they do not dehisce to spread the seeds abroad. |
 Click to enlarge! |
The plants are initially established in areas where water is plentiful, therefore invasion takes place especially in riverbeds and flood plains, and near watering places for stock, from where the plants spread rapidly to plains, |
 Click to enlarge! |
apron veld and even rocky ridges. |
 Click to enlarge! |
When conditions are favourable, a mature prosopis tree produces up to
1,000,000 seeds per annum. Sheep and game eat the seeds, which cannot be digested. However, the digestive process promotes germination even before the seeds are excreted in the manure. In soil, the seeds can lie dormant for up to ten years, but in manure, they germinate readily.
Prosopis seed is also spread by water. In addition, prosopis can be propagated vegetatively by growth nodes or knobs below the soil surface. If the aboveground parts of the plant die, new shoots can develop from the nodes. |
 Click to enlarge! |
Prosopis has no natural enemies in South Africa, and because they are so hardy, they easily survive serious droughts. The tree is particularly resistant to brackish water, which is otherwise totally unsuitable for agricultural use. This unique characteristic makes prosopis one of a very few dryland crops that can produce a large quantity of pods and
firewood from a very poor quality water.
During the late sixties, however, veld connoisseurs were shocked to realise that the spreading of the prosopis tree was reaching unprecedented proportions and, overnight, this previously popular tree was classified as an invader. Every land dweller in this country must therefore take note of prosopis and cooperate in eradicating it. In one district in the Great Karoo, it showed an in-crease of 400 % within 17 years. The result is an impenetrable stand of trees bearing no pods, and bare ground in the place of valuable Karoo grazing. This makes it clear why all Prosopis species have been proclaimed invaders in terms of the Conservation of Agricultural Resources Act (Act No. 43 of 1983). |
 Click to enlarge! |
Control measures are based on the principle that prevention is better than cure.
Regarding mechanical control: where light infestation occurs, small trees can be pulled up by hand during favourable moisture conditions. Young trees can be hacked out with a pickaxe, while big trees have to be chopped or sawn down and then be dug out of the ground with picks and spades. Seed-eating beetles are applied biologically to control the invader. The beetles penetrate the pods and then eat the seeds. These beetles, however, are merely supportive of other combative measures. |
 Click to enlarge! |
Regarding chemical control, the registered product, Tordon Super, has been developed. It can be sprayed or painted onto the trunks of the trees.
Promising results are being obtained when the tree is chopped or sawn down near the ground surface, and the agent is applied so that it can move down-wards on the stump. |
 Click to enlarge! |
With both mechanical and chemical combating methods, all growth nodes or knobs that occur to about 8 cm below the ground surface, must be destroyed permanently to prevent any
regrowth later.
The decision rests with the land dweller - prevent and combat the prosopis danger and ensure a future for yourself and your stock, or shut your eyes to the danger and take untimely leave of your most precious resource. |
AJ Wild & CG du Plessis
ELSENBURG / Extension
BEAUFORT WEST, LAINGSBURG
