1. Chinhoyi University of Technology Invasive Species Research and Management Unit TERRESTRIAL (LAND) INVASIVE SPECIES IN ZIMBABWE Jointed Cactus (Opuntia aurantiaca Lindley) Origin: South America in Argentina, Paraguay and Uruguay and is considered an invasive species in Australia and Africa Description: The Jointed Cactus is a thorny cactus species (Cactaceae family) that is usually less than half a metre high but can grow taller when supported by other adjacent plants. Damage caused by the species: Segments of clathodes are small and readily detach from the plant and take root, often below the plant. This results in the formation of thick and thorny impregnable stands of Jointed Cactus that deny access to animals to grazing areas and watering points. Jointed cactus is a declared noxious weed in Zimbabwe and South Africa. Biological control using the moth (Cactoblasis cactorum, Lipidoptera), the cochineal insect (Dactylopius austrinus, Hemiptera) and the moth (Mimorista pulchellalis, Lepidoptera) have met with limited success. For more information contact Professor A. B. Mashingaidze. Invasive Species Research and Management Unit, abmashingaidze@cut.ac.zw abmash@yahoo.com mobile 0774999054abmashingaidze@cut.ac.zw abmash@yahoo.com The black wattle, Acacia mearnsii De Wild Origin: The black wattle, Acacia mearnsii De Wild. (Syn. A. mollissima Willd.; Acacia decurrens var. mollis Lindl.) is a native of Australia (Tasmania, Victoria, Queensland, South Australia and New South Wales). Description: Acacia mearnsii is a small to large, evergreen, single- stemmed or multi-branched tree belonging to the sub-family Mimosoideae, familiy Fabaceae. It is a nitrogen fixing legume. Damage caused by the species: A. mearnsii was introduced into Zimbabwe in about 1902 and commercially plantations for tannin and charcoal production were established mainly in the eastern highlands starting in 1946. It has since spread out of control from abandoned plantations and neglected jungle stands and is now estimated to cover 200 000 ha, mostly in the mist-belt (1500 -1900 m a.s.l) in the eastern highlands, where it has displaced native species and forms thick impregnable forests in grasslands, mountain sides and river courses. It is not a threat in other regions of the country because of failure to reproduce Jumping cholla (Cylindropuntia fulgida (Engelm.) F.M.Knuth var. fulgida ) Origin: Arid deserts in north east Mexico and the south eastern United States. Description: The Jumping Cholla is an arborescent (tree –like), thony, low branching cylindrical cactus species that can grow to a height of 4-5 metres with drooping branches of chain fruits (hence chain fruit cholla) that belongs to the Cactus (Cactaceae) family. Damage caused by the species: The major problem to communities in Matebeleland where it is now endemic is that it forms impregnable physical barriers that deny them access to grazing land, agricultural land and watering points. The spines cause injury to domestic and wild animals and so far there are reports that villagers have lost cattle, donkeys and goats to the weed, valuable assets in the semi-pastoral agricultural system that sustains livelihoods in semi-arid areas of Zimbabwe. Lantana (Lantana camara) Origin: Tropical origin in northern and central south America and the Caribbean. Description: A perennial shrub from the verbena family of plants, Verbaceae, that forms thick and thorny impregnable thickets in grasslands, pastures, roadsides Damage caused by the species Damage caused by the species: Displaces indigenous species, reducing biodiversity and denying access to grazing areas. Lantana is toxic to livestock (cattle, sheep, goats and horses). The toxic substance found in Lantana plant parts is a triterpenoid that results in liver damage and photosensitivity. Although it is a declared noxious weed that farmers and communities are obliged by law to control and eradicate, it has continued to spread out of control throughout the country and is the most important invasive weed of pastures and rangelands in Zimbabwe. Fig 2: Cylindropuntia fulgida on a rocky outcrop near Manama Mission in Gwanda district, Matebeleland South Province, Zimbabwe (Courtesy of Hyde, Wursten and Ballings, 2007) Fig 2: Close up of jumping cholla spine with backward facing barbs that make it extremely painful and difficult to remove once they are imbedded in flesh