Dwarf amaranth

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.

Description

Dwarf amaranth seedlings are generally more prostrate than other Amaranthus species, with green leaves and purple leaf margins and veins. Mature dwarf amaranths have rounded leaves but are shorter than other amaranths and taper into a long stalk. Dwarf amaranth flowers are found in dense clusters in the leaf forks and are white or straw-coloured. Although smaller in height than other amaranth species, growing up to 30 cm tall, dwarf amaranths have fruit that are nearly double the size of other amaranth species. The fruit are 3-5 mm long, wrinkled and dark brown to almost black in colour when ripe.

Control

Germinating in spring, dwarf amaranths are best controlled when seedlings are young and actively growing. Dwarf amaranth seeds remain viable in the soil for a relatively short time, giving growers the opportunity to reduce numbers quickly with good weed 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

Amaranths

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.

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

Agrobase Australia (Viewed April 2020), ‘Dwarf amaranth (Boggabri weed)’, https://agrobaseapp.com/australia/weed/dwarf-amaranth

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

NSW DPI (Viewed April 2020), ‘Weeds and drought’, https://www.dpi.nsw.gov.au/biosecurity/weeds/weed-and-drought

White, M., Cheal, D., Carr, G.W., Adair, R., Blood, K. and Meagher, D. (2018), ‘Advisory list of environmental weeds in Victoria’, Arthur Rylah Institute for Environmental Research Technical Report Series No. 287, Department of Environment, Land, Water and Planning, Victoria, https://www.ari.vic.gov.au/__data/assets/pdf_file/0027/125919/ARI-Technical-Report-287-Advisory-list-of-environmental-weeds-in-Victoria.pdf