Download Australian Acacia - Botanical Society of South Africa

Weeds in our Area (Part One Hundred and Two)
By Bob and Ena McIntyre – Garden Route
BIOLOGICAL CONTROL CONTINUED
Lantana Camara
The early 1960’s saw renewed activity in the area of bio-control agents when two agents were
released during the course of 1961 for the control of Lantana camara. Lantana camara was an
obvious choice as it is considered one of the world’s 10 worst weeds and in our country poses a
serious problem in the coastal belt from the west coast right through to Mpumalanga into the
Northern Province. Without any doubt one of our most persistent alien invasive plants. Lantana
seeds are distributed by birds and in water during flash flooding. Wherever a stem comes into
contact with soil it will take root, effectively forming a new plant. Cut branches in contact with soil
will also readily take root.
All parts of the plant are toxic except for the ripe fruit and it is considered one of the most
common species in the poisoning of live-stock in South Africa. Left uncontrolled it forms dense,
impenetrable thickets, suppressing and out-competing indigenous vegetation with a very
detrimental effect on the environment.
Lantana originates from central and south America and has established itself as a serious problem
in India, Sri Lanka and other parts of the world. First recorded in South Africa in 1858 it spread
rapidly through KwaZulu-Natal and other eastern areas and like other invaders has worked its way
down the coast in a westerly direction.
Lantana camara‘s success as an invader can be ascribed to its very high variability – more than 50
different variants have been identified and it has been discovered that the different variants all
react differently to both herbicides and bio-control agents. Until 2006 twenty-one bio-control
agents had been released with varied success. The array of agents have ranged from leaf miners,
leaf chewers, stem gallers, sap suckers, flower feeders, leaf spot fungus, seed feeders and stem
borers. Some have had considerable impacts in certain areas but in stark contrast had been only
slightly effective or totally ineffective in other areas.
Lantana camara is easily identified: The plants are large scrambling shrubs with a robust
appearance; foliage is dark green, heart shaped, quite thick and furry to the touch and the stems
have many nasty short thorns. The crushed leaves exude a bitter unpleasant smell. Flowers are
attractive clusters of small bright pink/purple
and yellow flowers, fruits are small, juicy black
berries. Young plants are easy to weed out by
hand. However, older specimens become very
difficult to remove manually due to the spiky
stems and the tangled growth habit that forms
almost impenetrable thickets. The fact that
plants coppice readily after cutting necessitates
the application of a suitable herbicide to cut
stumps immediately after cutting.
Although it seems that overall biological control
agents have not been a major success in the
control of Lantana, it has most definitely had an effect in some areas.
Next time - some success stories about biological control on Australian Acacia species.
References: Problem Plants of SA – Clive Bromilow. Photo: Poster: Beautiful but Dangerous