Burr - Bathurst burr (Xanthium spinosum)

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Impact

Bathurst burr is amongst the most common and economically serious weeds in Australian agriculture. The burrs readily adhere to the wool of sheep. Wool contaminated by Bathurst burrs represents a substantial cost as additionally processing is required to separate the burrs. Bathurst burrs are also a significant weed of summer crops and horticultural crops.

Distribution

Bathurst burr is an annual weed which grows through the summer months in warm and temperate regions of the world. It has naturalised in New South Wales and currently ranges from the coast to the western plains. Bathurst burr was one of the first plants declared noxious in NSW in Urana Shire in 1907.

Description

Bathurst burr is a compact annual, summer growing herb. Stems produce many groups of 3-pronged, stiff, yellowish spines at the base of each leaf or branch. Leaves are dark green with prominent white veins, lighter underneath due to a covering of fine hairs. Leaves are divided into three irregular lobes. Burrs are 1 to 1.5 cm long, covered in numerous hooked spines. 

References

Auld BA and Medd RW (1999). Weeds. An illustrated botanical guide to the weeds of Australia. Inkata Press, Melbourne.

Parsons WT and Cuthbertson EC (2001). Noxious weeds in Australia 2nd Edn, CSIRO Publishing, Collingwood.

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Control

Cultivation

Cultivation is an effective method of controlling the seedlings of these weeds. Successive flushes of seedlings during the summer may require follow up control. Inter-row cultivation is commonly used in row cropping such as sorghum, corn and cotton to control seedlings that have germinated after irrigation events.

Slashing

Slashing or mowing are useful in clean-up operations after spraying with herbicide or if infestations are small and scattered. Any burrs from the plant should be removed from the equipment to prevent spread.

Chipping

Chipping or hand hoeing is only economical for small areas, individual plants or isolated populations. It is an effective follow up control method for plants not controlled by other methods to prevent seed set.

Surveillance

After controlling burr plants it is important to monitor these sites for further germination events. High risk areas for new infestations include flood prone areas or areas where stock from burr infested areas have been.

Pasture management

Maintaining ground cover in pastures is vital. Pasture gaps result in an increase in burr germination and seedling survival. It is important to ensure that pastures are not overgrazed in spring and summer to reduce the potential for the establishment of burrs and other weeds.

Grazing

Adult plants are not easily eaten by livestock, due to the roughness of the leaves and stems. Care needs to be taken when grazing to ensure there are no seedling plants, which are toxic to animals and could result in death.

Herbicides

Bathurst burrs are susceptible to a range of foliar and residual herbicides. 

Foliar herbicides are most effective if the plants are young and actively growing. Plants suffering from moisture stress are difficult to kill. Older plants may require repeat applications. Late control with some herbicides, when the burrs are green, can result in seed sterility – however this is not recommended as the primary form of control.

In crops, residual pre-emergent herbicides are useful, although there are sometimes problems as the burr can germinate and emerge from relatively deep in the soil, below the residual herbicide band. Follow-up control in the form of chipping or inter-row cultivation may be required. Spot spraying is an important tool for areas that are difficult to access and for scattered plants.

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 300 g/L + Picloram 75 g/L (Tordon® 75-D)
Rate: 1 L per Hectare
Comments: Boom spray application
Withholding period: 1-8 weeks (see label).
Herbicide group: I, Disruptors of plant cell growth (synthetic auxins)
Resistance risk: Moderate


2,4-D amine 625 g/L (Amicide® 625)
Rate: 80–110 mL per 150 L water
Comments: Spot spray. Seedlings only, actively growing.
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 3.3 L per hectare
Comments: Boom spray application, use higher rates on mature plants
Withholding period: 7 days
Herbicide group: I, Disruptors of plant cell growth (synthetic auxins)
Resistance risk: Moderate


Fluroxypyr 200 g/L (Starane™)
Rate: 75 mL per 100 L of water
Comments: Apply to actively growing plants.
Withholding period: 7 days.
Herbicide group: I, Disruptors of plant cell growth (synthetic auxins)
Resistance risk: Moderate


Fluroxypyr 333 g/L (Starane™ Advanced)
Rate: 45 mL per 100 L water
Comments: Apply to actively growing plants.
Withholding period: 7 days.
Herbicide group: I, Disruptors of plant cell growth (synthetic auxins)
Resistance risk: Moderate


MCPA 500 g/L (Various products)
Rate: 1-2 L/ha
Comments: Apply at seedling stage.
Withholding period: 7 days.
Herbicide group: I, Disruptors of plant cell growth (synthetic auxins)
Resistance risk: Moderate


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Biosecurity duty

The content provided here is for information purposes only and is taken from the Biosecurity Act 2015 and its subordinate legislation, and the Regional Strategic Weed Management Plans (published by each Local Land Services region in NSW). It describes the state and regional priorities for weeds in New South Wales, Australia.

Area Duty
All of NSW General Biosecurity Duty
All plants are regulated with a general biosecurity duty to prevent, eliminate or minimise any biosecurity risk they may pose. Any person who deals with any plant, who knows (or ought to know) of any biosecurity risk, has a duty to ensure the risk is prevented, eliminated or minimised, so far as is reasonably practicable.

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Reviewed 2014