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Common Name Alligator weed Botanical Name Alternanthera philoxeroides (Mart.) Griseb. Status Alligator weed is one of only fourteen weeds proclaimed as a State prohibited weed in Victoria. This is the highest category to which a noxious weed can be allocated and means that alligator weed is to be eradicated if possible from the State. Origin Alligator weed is a native of the Parana River system in north-eastern Argentina and is believed to have been introduced to Australia in shipping ballast. It has been grown as a home garden vegetable by Sri Lankan communities in major Australian cities, including Melbourne, and in some rural towns. Description Alligator weed is a perennial, stoloniferous herb. There are different forms of this plant which grow on land and in water. Aquatic forms may be free-floating, or rooted and emergent from the water surface. Plants in aquatic situations have larger, darker leaves, thicker stems with larger air spaces and grow more vigorously. Stems - prostrate or ascending, hollow, rhizomous; forming dense interwoven mats. Leaves - without stalks, dark green, smooth, waxy, 2 - 7 cm long, 5 - 40 mm wide, narrowing at the tip; in pairs opposite each other on the main stems. Veins originating from the central rib are easily visible beneath the waxy leaf surface. Flowers - silvery white, in heads 1.2 to 1.4 cm in diameter on stalks 2 to 7 cm long growing from between leaves and main stems; produced from January to March. Seeds - smooth, elliptical in shape and apparently rarely viable. Fruit - a flattened brownish bladder. Roots - short and fine in aquatic situations; thicker and longer in terrestrial situations, and may grow to a depth of about 60 cm.  Figure 1. Alligator weed Life Cycle Buds develop at nodes on the rhizomous stems in early spring and produce fast growing vertical stems. Flowering is from January to March. Vertical stems become prostrate in late autumn and winter adding to the bulk of plant material each year. Severe frosts may kill exposed stems. Dispersal Fragments of alligator weed stems are capable of producing new growth. The use of alligator weed as a vegetable is a major concern and probably the main cause for distribution interstate and within cities in Victoria. Seed production has not been observed in Australia. General Alligator weed causes major blockages of water flow in waterways such as irrigation canals and rivers. It readily establishes in and covers extensive surface areas of lakes. Alligator weed accumulates heavy metals and calcium oxalate which may be toxic to humans at certain levels. Alligator weed has been found at several hundred sites in Victoria. Most infestations are in back yards in suburban Melbourne, particularly in the south-eastern suburbs.  Figure 2. Alligator weed infestation. Chemical Control Under Victorian legislation there are controls on various aspects of the uses of agricultural chemicals. Some particular uses are prohibited and some require permits. Users of certain agricultural chemicals are required to obtain an Agricultural Chemical User Permit (ACUP) or work under the direct supervision of an ACUP holder. Additional restrictions on the use of some herbicides apply to particular geographic areas known as Chemical Control Areas (CCA). It is the responsibility of chemical users to familiarise themselves with these controls. See Agriculture Note: Agricultural chemical user permits (ACUP) and chemical control areas(CCA) for further information. Restrictions on use in CCAs apply to the chemical marked with a hatch (#). Contact the Regional Chemical Standards Officer of the Department of Natural Resources and Environment if further advice is required. You should read the product label and follow all label instructions carefully before using any herbicide. Use a product containing the following active constituent that is registered in Victoria to control alligator weed in the particular situation in which you need to use chemical control, eg. in aquatic situations. Consult the product label for detailed information on restrictions on use.
Products containing this active constituent are registered only for use in aquatic situations in Victoria. There are no chemicals registered for control of alligator weed in terrestrial situations in Victoria. This list of chemicals is based on information supplied to the Department of Natural Resources and Environment by the National Registration Authority for Agricultural and Veterinary Chemicals (NRA). The State of Victoria through the Department of Natural Resources and Environment has not assessed or checked the accuracy of the information supplied to it from the NRA as that responsibility rests with the NRA. Important Any person who believes they have located an infestation of alligator weed, regardless of the area, please notify a Catchment Management Officer at a local office of the Department of Natural Resources and Environment. References
Acknowledgements Prepared by R Williamson; KTRI 1996. Updated by I. Faithfull, KTRI, January 1998. Active constituents information supplied by Chemical Standards Branch December 1997. This note replaces note number PPA0003 The advice provided in this publication is intended as a source of information only. Always read the label before using any of the products mentioned. The State of Victoria and its employees do not guarantee that the publication is without flaw of any kind or is wholly appropriate for your particular purposes and therefore disclaims all liability for any error, loss or other consequence which may arise from you relying on any information in this publication. |
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© The State of Victoria, 1996 - 2008.
This document was published on 26/10/2008.