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Common Name Parthenium weed Botanical Name Parthenium hysterophorus L. Status Parthenium weed is one of only fourteen weeds proclaimed as State Prohibited Weeds in Victoria. This is the highest category to which a noxious weed can be allocated. As yet there is no known infestation of parthenium weed in Victoria. Origin Parthenium weed is native to the Caribbean. It is suspected that it was introduced to Australia during World War II. It is a major weed in Queensland and parts of New South Wales and in India. Description An upright annual herb in the family Asteraceae. Parthenium weed has a deep taproot and grows to a height of 30 to 150 cm. Stems - one main stem which branches in the upper half of the plant; grooved lengthwise, becoming woody with age. Leaves - deeply lobed with short hairs and light to mid green in colour. Rosette leaves are 8 to 20 cm longer, while stem leaves are shorter. Flowers - white to cream in colour. Both male and female flowers are on the one plant. Male flower heads consist of about 40 tubular florets and the female flower heads have 5 florets. Both type of heads are small, 4 to 10 mm across, and branch out from stems in clusters. Seeds - black, flattened, 2 mm long with two thin, white, spoon-like tails at one end. Roots - one main branched taproot with many finer roots. Life Cycle Parthenium weed establishes only from seed which can germinate any time of year given suitable moisture levels. Germination usually occurs in late spring or early summer. Plants commence flowering when they are 4 to 8 weeks old and may flower for several months. An individual plant may produce 15,000 seeds. Plants usually die in autumn.  Figure 1. Parthenium weed (scale in centimetres). Dispersal The seed is adapted to dispersal by water and to a lesser extent by wind. Spread is mainly along roads and stock routes. It is usually spread in mud or adhering soil by agricultural and road construction and maintenance machinery and livestock, and may possibly be dispersed to a limited extent in agricultural produce. General Parthenium weed exists in stock saleyards and roadside infestations in New South Wales despite control efforts. The potential to infest Victoria is very real. Parthenium weed is a vigorous colonist in poor and overgrazed pastures and readily occupies bare areas where stock movement is frequent. It does not invade most well managed crops and pastures but may be a problem even when present at low levels. Parthenium weed inhibits the growth and germination of other plants by allelopathy. Stock normally do not graze parthenium weed but may do so when there is no other feed. Meat of stock which do graze the weed is contaminated and not fit for human consumption. Grazing contaminated stock in areas free of parthenium weed for at least a month before slaughter can decontaminate the animals. Parthenium weed is known to cause allergic reactions in people. Symptoms are itching on exposed skin and development of a dermatitis which may spread over the whole body. It also causes asthma. The sesquiterpene lactone parthenin is the major allergen produced. 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. An ACUP is required for the use of prescribed chemicals containing the active constituents marked with an asterisk (*) in the following list. Records of the use of these chemicals must be made by the user and these records must be kept for 2 years. Restrictions on use in CCAs apply to the chemicals 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 one of the following active constituents or combinations of active constituents that is registered for use in Victoria to control parthenium weed in the particular situation in which you need to use chemical control, eg. in pastures. Consult the product label for detailed information.
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 parthenium weed, regardless of the area, please notify a Catchment Management Officer at a local office of the Department of Natural Resources and Environment. Parthenium weed infestations should immediately be quarantined. All livestock and machinery used in the area should be thoroughly cleaned. References Parsons, W.T. and Cuthbertson, E.G. (1992) Noxious Weeds of Australia. Melbourne, Inkata Press. Acknowledgements Prepared by Ross Williamson; KTRI, 1996. Updated by Ian Faithfull, KTRI, February 1998. This note replaces note number PPA0011 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.