Hoary cress: declared pest

Page last updated: Thursday, 12 September 2019 - 10:27am

Hoary cress, white weed, white top (Lepidium draba, formerly Cardaria draba) is a declared pest in Western Australia. This article describes the nature of the plant with links to requirements land owners/occupiers must adhere to, pest control methods and how to search, detect and report it.

Form: herbaceous — perennial

Status: present in WA

Appearance

Erect perennial herb 15-75 centimetres high, native of eastern Mediterranean and to central and southern Asia. It reproduces from seed, and from shoots from the perennial roots.

Stem: upright, branching near the top, covered with fine downy hairs, and longitudinally ribbed.

Leaves: leaves grey-green, covered with fine white hairs. Rosette and lower stem leaves up to ten centimetres long, oval to long-triangular and stalked; upper stem leaves up to eight centimetres long, alternate and oval with the narrow end attached.

Flowers: white, four to six millimetres in diameter, four petalled in dense terminal clusters; fragrant. Numerous flowers appear from September to November, in clusters at the tops of the stems.

Fruit: heart-shaped capsule two to four millimetres long, three to five millimetres wide, containing one or two seeds.

Seed: reddish brown, oval, about two millimetres long.

Spreads by movement of root sections and by seed. Regrows from perennial rootstock and from root fragments. Plants may produce up to 5000 seeds with high viability, although most spread is by movement of pieces of root during soil cultivation. Germinates in autumn and winter. In some locations in New South Wales, Victoria and South Australia it has been a major weed of many crops, including cereals and vegetables. In Tasmania it is a major weed of roadsides, railway lines and run-down pasture. In Western Australia it is a target for eradication.

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Agricultural and economic impact

Hoary cress can invade pastures, grain crops and horticultural crops. It has a very competitive deep perennial root system and can be allelopathic. It can taint milk and meat if grazed. Being in the cabbage family (Brassicaceae), it is likely to harbour diseases and pests that could attack canola and cruciferous vegetables.

Modelling indicates that hoary cress would cost Western Australia $6.2 million each year if it is not managed and $5.5 million if it is managed (Cook, D. 2014. Agricultural Resource Risk Management. Strategic Report. Impact Assessments for Declared Plants in Western Australia. July 2014, Department of Agriculture and Food, Western Australia)

Declared pest category

The Western Australian Organism List (WAOL) contains information on the area(s) in which this pest is declared and the control and keeping categories to which it has been assigned in Western Australia (WA). Use the following WAOL link to reach the declaration and declaration map for hoary cress.

Requirements for land owners/occupiers and other persons

Requirements for land owners/occupiers and other persons if this pest is found can be sourced through the declared pest plant requirements link.

Search > detect > report

MyPestGuide™ Reporter
via app or online
(Select 'Send report to MyWeedWatcher' from menu)
mypestguide.agric.wa.gov.au

Pest and Disease Information Service (PaDIS)
+61 (0)8 9368 3080
padis@dpird.wa.gov.au

Detectability: medium difficulty to find. Hoary cress can be distinguished by its greyish stems and leaves, and its many small white flowers carried at the shoot tips.

Who should look for it: grains industry, and horticulturists including orchardists, viticulturists and vegetable growers, biosecurity groups, landholders who have infestations of this weed, and other landholders in the vicinity of known infestations.

When to find it: hoary cress is most conspicuous when mature plants are flowering in spring and summer, with peak flowering in October-November. It persists over the rest of the year below-ground.

Where to find it: in WA hoary cress has been found occasionally in the Wheatbelt, but most infestations have been eradicated. In other parts of Australia and in other countries, hoary cress infests grain crops, horticultural crops, roadsides and railway lines.

Control method

Report the presence of this organism before undertaking a control measure. Control methods for this declared plant can be found through the hoary cress control link.

Management calendarTable displays: Search Aug-Nov. Dormant Jan-Mar. Germination Apr-Jun. Actively growing May-Nov. Flowering Sep-Nov. Fruiting: Oct-Nov. Treatment May-Oct.

Further information

Further information on hoary cress can be found on the hoary cress: what you should know page.

Contact information

Pest and Disease Information Service (PaDIS)
+61 (0)8 9368 3080
Technical support - MyPestGuide™