Spiny Emex

(Emex australis)
Spiny emex plant with fruits, image: Rod Randall, The Plant Protection Society of Western Australia

What is spiny emex?

Spiny emex is a weed of pasture and crops.
Spiny emex is a declared weed in Tasmania under the Tasmanian Weed Management Act 1999. The importation, sale and distribution of spiny emex are prohibited in Tasmania.

How to identify spiny emex

Spiny emex is an annual herb that is usually prostrate (ground-hugging) but which may grow erect when growing among tall plants. Normally a rosette of leaves forms around the crown from which numerous trailing stems develop. Stems are purplish at the base and the leaf nodes, growing to 50 cm long.
The leaves are triangular to oval shaped, while the flowers grow in the leaf axils and are small and inconspicuous. Spiny emex fruits go from green to brown as they ripen, are hard and woody, and triangular with three rigid and sharp spines.
Seeds germinate at any time but mainly in autumn and winter. Flowering occurs from late winter to early summer. Spiny emex as young as 6 weeks old can produce fruit.
For help in identifying spiny emex, search the Dennis Morris Weeds and Endemic Flora database for spiny emex illustrations. If you are still in doubt about the weed you are dealing with, contact Biosecurity Tasmania on 03 6165 3777 for help.

Image top: Spiny emex plant with fruit, © Rod Randall, Plant Protection Society of Western Australia.
Image above: Spiny emex fruit, © Julia Scher.

Spiny emex in Tasmania

The distribution of spiny emex is very limited in Tasmania. Spiny emex has been recorded on Flinders Island and occurs near South Arm in the state's south. Spiny emex prefers drier, sandy soils, and occurs as an occasional weed of pastures, roadsides and neglected areas.
Spiny emex is a weed of pastures and crops and is toxic to stock. Severe infestations can significantly reduce pasture productivity and crop yields. Although not readily eaten by stock, spiny emex can cause sheep deaths due to poisoning. The spiny fruit can also cause inconvenience to barefooted people, cyclists, and can cripple dogs working in infested areas.

What is the legal status of spiny emex in your area?

The legal responsibilities of landholders and other stakeholders in dealing with spiny emex are laid out in the Statutory Management Plan for Spiny Emex
Use Table 1 (Zone A municipalities) in the Statutory Management Plan for Spiny Emex to find out whether this weed occurs in your municipality.

Detailed management and control guidelines for spiny emex can be found in the Spiny Emex Control Guide. Refer also to Herbicides for Spiny Emex Control. For further information see Weed Links and Resources.

Spiny Emex Control Guide

Do

Plan your control program, this will save time and money in the long-run;
Consider the impact of your control methods on off-target species, especially if herbicides are used;
Ensure machinery and equipment is washed down between sites or prior to contractors leaving site;
Get in early - for new infestations, eradicate before the plants reach the flowering stage: once plants begin seeding, control becomes more difficult and expensive;
Carefully time your use of herbicide for best results (see Herbicides for Spiny Emex Control for more information);
Coordinate your control program with neighbouring landholders where your weed problem crosses property boundaries;
Revisit and regularly inspect the site and ensure follow-up is undertaken;
Use a combination of different control methods;
Establish vigorous pasture (or native species) after removal to reduce re-infestation; and
If drought feeding use a defined drought feedlot area to limit potential introduction of the weed and aid future control.

Don't

Don't introduce spiny emex to spiny emex-free areas (e.g. by failing to wash down machinery and equipment between sites);
Don't start your control program without first planning your approach;
Don't allow spiny emex to flower and set seed before treatment;
Don't rely on one attempt at removal - follow-up is essential; and
Don't rely on just one control method.

Spread of spiny emex

Spiny emex reproduces by seed.
The fruit is well adapted for dispersal, with the spines attaching to shoes, tyres, the feet of animals and containers of produce.
Spiny emex fruit can be spread as a contaminant of fodder and agricultural seed, as well as by water along watercourse and during floods.
The fruit can live for 4 years in the soil.

Avoid the introduction of spiny emex

Avoid the use of fodder and poorly graded seed from infested areas which may contain spiny emex fruits.

Physical removal

Isolated plants can be grubbed. Because fruit can develop at an early age, aim to remove all plants shortly after emergence.
Follow up control is required as seedlings continue to appear for several years.

Cultivation

Cultivation will kill seedlings. However due to the length of the germination period, cultivation needs to be used in conjunction with herbicide treatment.
Start with a shallow cultivation in late summer to encourage as much germination as possible after autumn and early winter rains.
Continue to cultivate while controlling any emerging spiny emex with herbicide.
Avoid deep ploughing as this buries seed, which can be brought back to the surface to grow in later cultivations.

Chemical control

A number of herbicides are registered for use on spiny emex in Tasmania. See Herbicides for Spiny Emex Control for more information.

Herbicides for Spiny Emex Control

Important Disclaimer

To the extent permitted by law, the Department of Natural Resources and Environment Tasmania (including its employees and consultants) excludes all liability to any person for any consequences, including but not limited to all losses, damages, costs, expenses and any other compensation, arising directly or indirectly from using information or material (in part or in whole) contained on this website.