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March 2014

As promised last month, our next “candidate” is the notorious weed Lantana camara. Regrettably Lantana is all too well known over much of the world, due to its potential as a plant with ornamental horticultural value. Plant breeders selected and hybridised it into hundreds of varieties that were distributed worldwide.


Lantana is native to tropical, central and Southern America (Mexico, parts of the Caribbean, Venezuela and Colombia). It has now invaded large areas in India, Sri Lanka, Australia and much of Africa. It is also apparently a problem in Florida, Texas and Hawaii. It was first introduced into South Africa in 1858 (Cape Town) and 1883 (Durban) and was eventually declared a noxious weed in S.A. in 1954. It is now a category 1 declared weed and control or eradication by landowners is compulsory.


It escaped into natural systems and agricultural land chiefly through the movement of frugivorous birds. It is tolerant of animal browsing, drought, frost and fire and apparently secretes chemicals to suppress competitors. It also spreads vigorously by coppicing.Most parts of the plant are toxic to bovines and horses causing photosensitivity and widespread losses have occurred in the USA, RSA, India and Australia.

Description of plant: A compact floriferous shrub or untidy scrambler up to 2m. or higher.


Young stems: Almost square, usually covered with short, stiff hairs and re-curved prickles, but sometimes un-armed.


Leaves: Dark green, paler below, opposite, rough and hairy, becoming smoother.Crushed leaves are pungent smelling and are a skin irritant.


Flowers: Multi coloured, in compact, flat-topped heads, florets opening yellow/white, becoming pink orange and red, often with several colours in one head.


Fruit: Berry-like clusters, glossy green turning purplish-black when ripe.


Control: Small plants can be hand pulled when soil is moist. Mature plants are difficult as different hybrids differ in their susceptibility to herbicides and to natural enemies. The best method is a rigorous combination of mechanical plus chemical control and annual follow-up treatments. Chopping the dense bushes and then painting the stumps or spraying the regrowth with herbicide is the usual and most effective method. Plants taller than 1m. need to be cut back and a cut stump treatment applied.Herbicides recommended for this purpose are: a 5% solution of Hatchet or Chopper or 2% solution of Plenum in water. Re-growth and plants up to 0.5m. can be foliar sprayed with a 1% solution of Plenum or 3% solution of Roundup (glyphosate) in water, plus a 0.5% solution of any wetter product.


Bio-agents reduce the frequency and cost of control by slightly reducing growth rate, reproduction, spread and density of infestations. Currently used bio-control agents are Petiole galler (Caelocephalapion camarae) and Root feeder (Longitarsus bethae).
Sources:

  • Sapia News and Aric website
  • Alien Weeds & Invasive Plants (L. Henderson)
  • Problem Plants of S.A. (C. Bromilow)

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February 2014

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March 2014

As promised last month, our next “candidate” is the notorious weed Lantana camara.

Read more