1. Chinhoyi University of Technology Invasive Species Research and Management Unit EMERGING (NEW) AQUATIC INVASIVE SPECIES IN ZIMBABWE Parrot’s feather ( Myriophyllum aquaticum (Vell.) Verdc. ) Origin: Native to the Amazon River in South America Description: A perennial plant that gets its name from its feather like leaves that are arranged around the stem in whorls of four to six. Stems and leaves are submerged in the water but also emerge above the water and can grow more than 30cm above the water looking like small fir trees. The woody emergent plants extend to the bank and shore and can grow 1.5m tall. Only female plants exist outside its native range and it does not reproduce sexually as an alien invasive species. It establishes from stem segments, asexually. Stem apices are better than other plant parts as vegetative propagules, therefore during mechanical control there is need to limit the number of loose stem apices produced and they should not be allowed to drift down stream where they can start new infestations of the weed. Damage caused by the species: The aquatic plant can cover large areas of lakes and ponds especially towards the shore and impede access and navigation to fishing, recreational and tourism facilities. In Lake Chivero, water hyacinth covered 35% of the Lake surface, (36.6%) and Parrot’s feather covered only 1.7% in 1985. Ten years later in 1995, the estimated weed coverage was water hyacinth 3%, P. stratiotes 0.3%, Parrot’s feather (4%) and Azolla filiculoides (1%). In 2000, weed coverage was water hyacinth 2.4%, P. stratiotes 0.8%, Parrot’s feather 6.8% and Azolla filiculoides 3.5% (Chikwenhere, 2001). The emergence of Parrot’s feather as a major invasive aquatic weed species in Lake Chivero is a result of a combination of lack of natural enemies and competition from dwindling populations of water hyacinth and through chemical, mechanical and biological control and P. stratiotes as a result of biological control (Chikwenhere, 2001). Integrated management of all species is recommended to prevent new species occupying the ecological space created by the effective control of one or more species in the Lake. 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.zwabmash@yahoo.com Like all other aquatic weed species, spaghetti weed forms thick mats that impede navigation of the lake and river by boat for recreational and commercial purposes. Access to fishing and other tourism facilities is denied. The weed changes the aquatic habitat by using up oxygen in the water and decomposing mats of the weed may further deoxygenate the water and cause fish kills. The weed slows down water movement in irrigation canals and blockages of canals may cause flooding. The weed has potential to causes massive losses in water from reservoirs through transpiration. The ability of the weed to slow down water currents increases breeding habitat for the malaria causing anopheles mosquito. Other disease vectors such as Mansonioides mosquitoes, the vectors of human lymphatic filariasis causing nematode Brugia, can breed on this weed. Spaghetti Weed/ Pennywort (Hydrocotyle ranunculoides) Origin: Native to North and South America and parts of Africa Description: Spaghetti weed belongs to the family Apiaceae (the carrot family). It spreads through vegetative extension of rhizomes that root at nodes and by seed. The rhizomes float in water. Leaves grow on petioles up to 35 cm long and are round to kidney shaped with 3-7 lobes. Flowers are small, white to pale yellow and fruits are small achenes than can float, helping in dispersion of the seed. Damage caused by the species: In Manyame riverine system and Lake Chivero in 1985, the water was covered by the following aquatic weeds; water hyacinth (35%), Pistia stratiotes(36.6%) and Myriophyllumm aquaticum (1.7%). By the year 2000, as a result of mechanical, chemical and biological of water hyacinth and biological control of water lettuce (Pistia stratiotes), Spaghetti weed (Hydrocotyle ranunculoides) invaded Lake Chivero and covered 9.5% of its surface ( Chikwenhere, 2001). Flowers form umbrella like clusters (umbels) and fruits are dehiscent achenes the float in water. The seeds germinate in sediments on the shores of the river or lake and small seedlings detach from the sediments and float in the water For more information contact Professor A. B. Mashingaidze. Invasive Species Research and Management Unit, abmashingaidze@cut.ac.zw abmash@yahoo.com mobile 0774999054 abmashingaidze@cut.ac.zwabmash@yahoo.com