Last update: August 16, 2011 03:47:07 PM E-mail Print

 

The prosopis - methods to control the problem

Dr Helmuth Zimmermann

assistant director, Plant Protection Research Institute

Pretoria

and

Mr Gert Coetzer

senior pasture ecologist,

Rumevite, Johannesburg

 

PROSOPIS does have a number of uses.

 

Disadvantages of the prosopis:

 

Biological control

Beetles were imported about 5 years ago to help control the prosopis. The beetles prefer the mature pods of the trees. It takes about 4 years to get maximum gain from the beetle. A problem with the beetle as biological control, is that the pods are distributed through the manure of the animals. The beetle then does not eat the pods.

 

Other options of biological control:

Go ahead with the destruction of the seed and import even more beetles. The trees are not damaged. This method takes about 6 years to be effective, but is relatively cheap.

Destroy the blossoms and the seed. Insects that destroy the blossoms are found in the USA. It is therefore possible to obtain total destruction.

 

Other methods of control

Burning of the trunk. The tree must have a single trunk. A dung ire is made around the trunk. The fire must be warm and must smoulder for at least 12 hours. The growing points are burnt dead. The only problem is that some of the growing points are up to 5 cm beneath the ground.

A bulldozer can be used. Not all the trees are destroyed and the seedlings that survive will grow again.

 

The prosopis must be sawn off 15 to 20 cm above ground. The parts that remain must be sprayed thoroughly with Tordon Super

 

Chemical control

Spraying of the leaves. Prosopis takes up the toxicant through the leaves. This can only take place under ideal conditions. Most of the intake takes place during the period of active growth and there must be no sign of stress conditions. Prosopis grows in dry areas. The leaves are therefore under stress and the spraying is not successful.

Tordon 101 is used for spraying the leaves. It is mixed with water. The water cannot penetrate the bark and the trunk has to be chopped so that the toxicant can penetrate the trunk.

Penetration through the bark and the trunk. Tordon Super can be used with success since it is taken up by the trunk and not through the leaves. Tordon Super is mixed with diesel, which makes penetration easier.

The trunk must be sawn off about 15 cm above the ground. It must be sprayed thoroughly with Tordon Super to cover all remaining parts of the trunk.

 

Published

Karoo Streeknuusbrief no 2, 1992