Amaranth

Amaranthus spp.

Amaranths are a group of broadleaf weeds that are particularly problematic in broadleaf vegetable crops and summer crops such as cotton. Species include green amaranth (Amaranthus viridis), dwarf amaranth (A. macrocarpus), Boggabri weed (A. mitchelli) and redshank (A. cruentus). Tumbleweed (A. albus) is a more temperate weed, found in crops and roadsides in NSW, Vic, SA and WA. In addition to having key weed attributes of rapid growth rates, being prolific seeders, high genetic diversity, and the ability to tolerate a range of growing conditions, some amaranth species, such as Palmer amaranth, have developed resistance to glyphosate in the USA.

Refer to the link below for more detailed information on specific amaranth species.

Description

There are approximately 70 different species of predominantly annual amaranths. They are characterised by broad, branching leaves which are rhombic or egg-shaped. They have prominent leaf veins, which are commonly green or red and a distinctive single flower spike often containing both male and female flowers.

Control

Roundup Ultra® MAX, Roundup Ready® Herbicide with Plantshield® and Roundup Ready PL are registered for the control of amaranth species in a range of situations.

Related Pests

Dwarf amaranth - Boggabri weed

Amaranthus macrocarpus var. pallidus and var. macrocarpus

Dwarf amaranth is an annual herb that is most commonly a weed of irrigated summer crops and fallows in eastern Australia. Dwarf amaranths can also be a pathogen host for some cotton diseases. It is more commonly associated with, but not restricted to, clay soils. Dwarf amaranths like other amaranths, grow quickly, are prolific seeders and can tolerate a range of growing conditions.

Refer to the link below for more detailed information on specific amaranth species.

Green amaranth

Amaranthus viridis

Green amaranth is widely naturalised in many parts of Australia but is more commonly associated with the coastal fringes. In addition to being a cropping weed, it is also a very common garden weed. Green amaranth, like other amaranths, grows quickly, is a prolific seeder and can tolerate a range of growing conditions.

Refer to the link below for more detailed information on other amaranth species.

Redshank

Amaranthus cruentus, Amaranthus retroflexus

Redshank, like other amaranths, grow quickly, are prolific seeders and can tolerate a range of growing conditions. In mainland Australia, Amaranthus cruentus is found in southern states, most commonly as a horticultural weed. In Tasmania, redroot amaranth (Amaranthus retroflexus) is also referred to as redshank.

Refer to the link below for more detailed information on specific amaranth species. Note: Persicaria maculosa is also referred to as Redshank, but is not dealt with here.

References

Fleming, J, McNee, T, Cook, T and Manning, B (2012), ‘Weed control in summer crops 2102 – 2013’, NSW Department of Primary Industries, https://www.dpi.nsw.gov.au/__data/assets/pdf_file/0008/248471/Weed-control-in-summer-crops-2012-13.pdf

Herbiguide (2014), ‘Amaranth’, Herbiguide, http://www.herbiguide.com.au/Descriptions/hg_Amaranth.htm

Khan, A., Hereward, J., Werth, J., Walter, G. and Chauhan, B. (2017) ‘Amaranthus: Emerging weeds of cotton systems in Australia?’, Cotton Research Conference, 5-7 September 2017, Canberra, http://era.daf.qld.gov.au/id/eprint/6347/

PlantVillage (Viewed April 2020), Plant Village, https://plantvillage.psu.edu/topics/amaranth/infos