Cayenne snakeweed is an opportunistic weed that can rapidly invade pastures, sugar cane crops, neglected areas and roadsides. It will quickly spread and thrive when ground cover is reduced or excluded, such as newly sown pastures or crops, cleared areas and overgrazed pastures.
Disturbed native vegetation areas are at risk of invasion. Cayenne snakeweed can quickly out-compete and eliminate native species.
Snakeweeds are native to the tropical Americas, extending from the Caribbean through to Argentina. Cayenne snakeweed has naturalised in many tropical parts of the world including Madagascar, tropical Africa, Oceania, south-eastern USA and tropical Asia.
Originally introduced as an ornamental plant, four species have now naturalised along the coastal areas of Queensland, the Northern Territory and Western Australia. All are considered weeds. Cayenne snakeweed is predominantly found along the eastern and northern Australian coastlines, particularly northern Queensland and the Northern Territory.
At present, cayenne snakeweed is not known to occur in NSW.
Cayenne snakeweed only reproduces from seed. The seeds of cayenne snakeweed can be dispersed in contaminated fodder, hay and pasture seed. It can also be spread from the movement of contaminated soil and garden refuse.
Seeds germinate all year provided there is enough soil moisture. This is usually following summer rain. Young plants grow quickly and flower in the late summer of their first growth season. Once established, new stems are produced continuously.
Flowering and seed set occurs throughout the year but is most abundant during spring, summer and autumn.
Cayenne snakeweed is an evergreen, clumping perennial shrub. It can grow up to 2.5 m high but more commonly reaches 1.5 m. It is distinguished by long, curved and snake-like flower heads.
Cayenne snakeweed thrives in tropical or subtropical climates with annual rainfalls above 1000 mm. It is more often found in wet coastal regions, along waterways and adjacent pasture areas.
Written by Rachele Osmond.
Biosecurity Queensland (2014) Fact sheet PP52–Snakeweed: Stachytarpheta spp. Department of Agriculture, Fisheries and Forestry, Brisbane. Available at http://www.daff.qld.gov.au/__data/assets/pdf_file/0005/54392/IPA-Snakeweed-PP52.pdf
Department of Employment, Economic Development and Innovation (2011) Dark blue snakeweed: Stachytarpheta cayennensis. Queensland Government Available at http://keyserver.lucidcentral.org/weeds/data/03030800-0b07-490a-8d04-0605030c0f01/media/Html/Stachytarpheta_cayennensis.htm
Hosking JR, Sainty GR, Jacobs SWL & Dellow JJ (in prep) The Australian WeedBOOK
Parsons, WT and Cuthbertson, EG (2001) Noxious weeds of Australia, CSIRO Publishing, Collingwood.
Pasture management is an important component of cayenne snakeweed control and should be incorporated into the integrated weed management program.
Heavy infestations required destocking, physical and chemical treatment, followed by pasture re-establishment.
Individual plants within small infestations can be physically pulled or grubbed out. Take care to remove larger roots.
In large infestations, physical control will need to be conducted together with chemical control to obtain the best results. Slash infestations prior to flowering. Follow with foliar herbicide treatment on actively growing plants.
Continued follow-up and re-treatment is essential to maintain control.
Foliar spray larger infestations when plants are actively growing. Best results are achieved during summer months.
Small infestations can be spot sprayed using a foliar application.
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The requirements in the Noxious Weeds Act 1993 for a notifiable weed must be complied with