Grain Guide 2017

GRAANGIDS

2017

GRAIN GUIDE

Acacia saligna

Lantana camara

Continued on p. 79

Acacia saligna

(Labill.) H.L. Wendl

The Port Jackson willow is indigenous to Australia and is described as a perennial shrub or small

tree that can grow to between 3 m and 7 m tall. It grows in a variety of soil types and occurs

particularly in disturbed areas or road reserves. It has an extensive root system comprising a

well-developed taproot and several shallow, lateral roots. This tree grows rapidly and its useful

life is between 15 and 20 years. Many seeds are produced per plant and they are also the main

propagation mechanism.

The negative aspects of the Port Jackson willow include the

following: it competes for light, space, water and nutrients;

it displaces indigenous vegetation quickly; it changes the

landscape and habitat; the seed is a contaminant; obstruction

– dense stands restrict the movement of animals; in water and

river courses it causes an obstruction to water flow; it forms an

obstruction in terms of vision; consumes large quantities of wa-

ter; reduces the grazing capacity and biodiversity if dense stands

occur. The total hectares invaded by this tree is

1 852 155 ha

If all these trees were to be placed in one spot, they would oc-

cupy

108 004 ha.

The calculated annual water consumption

of this tree is

171 million m

A rust fungus and seed-eating snout beetle act as biological con-

trol agents on the plants – the bio-agents are very effective and

should be employed as the first control mechanism. Although

very hot fires can cause the tree to die, it is not recommended as

control method, as fire will promote seed germination. Mechanical control alone is not recom-

mended, as sprouting will occur. Various chemicals are registered to control the plant and can be

useful in combination with mechanical control. According to the CARA Act the Port Jackson willow

is classified as a category 2 plant – it may occur only in a demarcated area if permission for this

has been obtained. (Any plants outside the demarcated area must be controlled.) If the landowner

does not have permission, it must be controlled. According to NEMBA it is a category 1b plant – it

is therefore an alien species that should be controlled, removed and destroyed if possible. No

trading in this plant may take place.

Lantana camara L

Lantana originally comes from Central and South America. It is an erect to spreading thorny

shrub. It has a well-developed root system and does not display specific habitat preferences – it

therefore occurs in various areas in a variety of soil types. Propagation of the lantana is usually

through seeds that are often disseminated by birds, but new plants can also develop from

the rhizomes. It is globally regarded as one of the major

weed species.

The negative aspects of lantana are the following: It

competes for light, space, water and nutrients; it displaces

grasses; it inhibits the growth of grass (is allelopathic); it

changes the landscape and habitat, particularly if it occurs

in dense stands; it is toxic to animals; it is thorny; the seed is

a contaminant; it causes obstruction (access, cultivation, vi-

sion); increases erosion; reduces soil binding; forms impene-

trable stands; reduces the grazing capacity and biodiversity if

in dense stands and reduces the biodiversity of invertebrates

in the soil. Lantana invasion covers about

2 235 395 ha

– if this area is condensed so that the trees represent 100%

invasion, it would cover

69 211 ha.

The calculated annual

water consumption of lantana is

97 million m

Various