Hoary cress (Lepidium draba)

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Impact

Hoary cress is an invasive plant of pastures, cereal crops, horticultural crops, roadsides and neglected areas. In cropping systems, hoary cress can significantly reduce crop yields, interfere with harvesting and is a grain contaminant. As it is part of the Brassica family, it poses a major problem when canola is part of the cropping rotation, as it cannot be controlled in-crop. In grazing situations, it can taint the meat and milk of animals that eat it.

Distribution

A native to the eastern Mediterranean, through to central and southern Asia. Hoary cress is a weed in Europe, the Middle East, South Africa, New Zealand and the USA.

Thought to have entered the country as a grain contaminant. It is now present at various locations and densities throughout the cropping areas of New South Wales, Victoria, South Australia, Tasmania, southeast Queensland and southern Western Australia. 

Spread

Hoary cress can reproduce by seed, although most new plants arise from its spreading roots and broken root segments. The well developed lateral roots produce new shoots from buds that occur along its length. Cultivation is a common cause of root spread. Thousands of seeds are produced per year by each plant, with around 80% viability. Seeds can be spread by contaminated soil, hay, grain, vehicles and equipment.

Lifecycle

Seeds germinate in autumn. New growth from root buds will also occur in autumn. Seedlings grow and develop during the winter and spring.  Flowering stems begin to emerge from early spring, with flower heads developing through to late spring. It is uncommon for plants that have germinated from seed to flower in their first year.  Instead they use their energy to develop a deep and extensive root system.  Stems die back in summer after flowering and remain dormant until autumn. 

Description

Hoary cress is an erect perennial herb capable of growing to 90 cm tall, but more commonly reaches heights of 75 cm.

Stems

  • upright
  • branched near the top
  • covered in fine hairs
  • has ribs that run the length of the stem

Leaves

  • covered in soft, fine hairs
  • greyish green or bluish green in colour
  • occur alternately along the stem
  • variable shape from oblong to wedge-shaped
  • lower leaves occur on short stalks, are long and narrow (up to 10 cm long) with toothed edges
  • the base of upper leaves clasp the stem

Flower

  • white, 4–6 mm in diameter
  • 4 small petals, up to 4 mm long
  • occur at the end of branches in dense flat-topped clusters
  • fragrant

Fruit

  • heart-shaped capsule
  • 2–4 mm long and 3–5 mm wide
  • separates into 2 parts when mature
  • contains 1–2 seeds
  • mature fruit has a network of veins on surface

Seed

  • reddish-brown in colour
  • about 2 mm long
  • oval

Roots

  • woody taproot reaches to about 2 m deep
  • branched lateral root system, producing shoots at irregular intervals

Habitat

Hoary cress prefers warm, temperate conditions with an annual rainfall over 400 mm.  It can grow in a variety of soil types, but prefers alkaline loams. It will thrive in loose, rich soils that allow rapid lateral root growth.

References

Department of the Environment (2011) Weeds in Australia: Lepidium draba. Australian Government. Available at: http://www.environment.gov.au/biodiversity/invasive/weeds/identification/index.html 

Hosking JR, Sainty GR, Jacobs SWL & Dellow JJ (in prep) The Australian WeedBOOK.

Lamp C and Collet F (2004) Field guide to weeds in Australia, Inkata Press, Melbourne.

Parsons, WT and Cuthbertson, EG (2001) Noxious weeds of Australia, CSIRO Publishing, Collingwood.

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Control

To control hoary cress, property hygiene practices should be in place to restrict movement of roots and seed into clean areas.

Avoid using cultivation as broken root pieces can increase infestations or spread the weed to new locations.

Herbicides

Herbicides should preferably be applied when the plant is in its rosette form, is actively growing and before flowering. This is usually from winter to autumn.

Herbicide can be applied as a spot spray or boom spray application, depending on the herbicide chosen.

Follow up treatments will be required.

Herbicide options

WARNING - ALWAYS READ THE LABEL
Users of agricultural or veterinary chemical products must always read the label and any permit, before using the product, and strictly comply with the directions on the label and the conditions of any permit. Users are not absolved from compliance with the directions on the label or the conditions of the permit by reason of any statement made or not made in this information. To view permits or product labels go to the Australian Pesticides and Veterinary Medicines Authority website www.apvma.gov.au

See Using herbicides for more information.


2,4-D amine 625 g/L (Amicide® 625)
Rate: 1.1–1.7 L/ha
Comments: Boom spray application, at rosettes to pre-flowering.
Withholding period: 7 days.
Herbicide group: I, Disruptors of plant cell growth (synthetic auxins)
Resistance risk: Moderate


2,4-D LV ester 680g/L (Estercide® Xtra)
Rate: 1.7 to 2.1 L/ha
Comments: Boom spray application, from late rosette to pre-flowering
Withholding period: 7 days
Herbicide group: I, Disruptors of plant cell growth (synthetic auxins)
Resistance risk: Moderate


Glyphosate 360 g/L (Roundup®)
Rate: 500 mL per 100 L of water
Comments: Spot spray application.
Withholding period: Nil.
Herbicide group: M, Inhibitors of EPSP synthase
Resistance risk: Moderate


Glyphosate 360 g/L (Roundup®)
Rate: 1.5 L/ha
Comments: Boom spray. July to September, late rosette to flowering.
Withholding period: Nil.
Herbicide group: M, Inhibitors of EPSP synthase
Resistance risk: Moderate


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Legal requirements

The content provided here is for information purposes only and is taken from the Noxious Weeds Act 1993.

Area Class Legal requirements
Murray River (formerly Wakool) 4 Locally Controlled Weed
The growth of the plant must be managed in a manner that continuously inhibits the ability of the plant to spread only in the area formerly known as Wakool Shire Council

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For technical advice and assistance with identification please contact your local council weeds officer.
For further information call the NSW Invasive Plants and Animals Enquiry Line on 1800 680 244 or send an email to weeds@dpi.nsw.gov.au

Reviewed 2014