Bathurst Bur
Xanthium spinosum
DESCRIPTION
Bathurst bur is a very nasty weed that is subject to Pest Plant Management in several regions of New Zealand. Details for your region, including your responsibilities, are available from your regional council.
In spite of its name, Bathurst bur originates not from Australia’s V8 Mecca, but from South America. It’s an erect, multi-branched annual herb growing to about a metre in height. The upright stems carry distinctive yellowish triple spines to 3cm long, grouped in opposite pairs at the base of each leaf. The stem itself is stiff and downy, and whitish in colour.
The somewhat similar Noogoora bur lacks the triple spines of Bathurst bur and also has larger leaves. The leaves of Bathurst bur are slender and sharply pointed, up to about 10cm long, and are dark green and shiny with white mid-ribs on the upper surfaces, but pale and dull on the undersides. Flowers are pale green, small and inconspicuous. Flowering occurs from December through to April.
The root system of the Bathurst bur consists of a long taproot. The fruit is what gives this plant its name (well, the second part of its name). These are the woody oval-shaped burs, up to 13mm long, and covered with a layer of thick hooded prickles that hook firmly to clothing and to the wool of sheep. It is by this tenacious method that the Bathurst bur is mostly spread; inside each bur are two seeds.
As well as having an obvious detrimental effect on wool, the burs are irritating to the skin of shearers and damage the combs of the shearing handpiece. The sharp and difficult-to-remove burs also cause foot damage to stock.
The seedling plant is also poisonous to stock, in particular to horses and pigs. And to round out the rap sheet of this unpleasant pest, the Bathurst bur is a host of fungal diseases of common horticultural plant species.
HABITAT
Although not a common plant, Bathurst bur occurs in parts of Northland, Auckland and Hawkes Bay, less frequently in the lower half of the North Island, and also at scattered sites throughout the South Island. It invades pasture, especially in high-fertility and warmer coastal areas, and is also found in wasteland, arable land, summer crops and horticultural sites. It is frequently seen around stockyards, gates and races; the areas where the animals carrying the bur concentrate.
MANUAL CONTROL
Isolated plants can be grubbed out and must be removed and burned because the burs of a dead plant will still drop to the ground and deposit the seeds within. The seeds remain viable in the soil for many years. For that reason, even patches of Bathurst bur that are sprayed (see below) must still be manually removed and destroyed after spraying.
HERBICIDE CONTROL
Cut'n'Paste or Paint Herbicides to kill Bathurst Bur
Cut off the entire Bathurst Bur plant as close to the ground as possible, and immediately hand spray, swab stumps with this mixture:
- 1g MSF600 plus any of the following types of glyphosate
- 100ml G-360 GLYPHOSATE + 10ml SuperWetter per 1L of water., or
- 67ml G-540 GLYPHSATE + 10ml SuperWetter per 1L of water., or
- 45g Granny Herbicide + 10ml SuperWetter per 1L of water.
Or a simple clean and quick method to control Bathurst Bur is to use Cut'n'Paste Glimax Professional or Cut'n'Paste Bamboo Buster gels applied from the convenient brush-on-bottle, onto the freshly cut stems.
Spraying before burs are formed is essential to reduce the chances of regrowth. Sprayed sites, especially if burs were present at spraying, will need to be monitored for several seasons to intercept any fresh germinations early. And it is essential to not allow any sprayed plants with burs to remain on the site even if dead.
Herbicide Spot Spraying to Kill Bathurst Bur
All situations where spraying is required will effectively be spot spraying jobs, whether of a few individual plants or of patches of denser plants. Remember that this is a notifiable pest plant, and some local authorities will provide control resources.
Several Bathurst Bur weed killers are effective, and the choice comes down to what product is on hand and, to a lesser extent, the situation in which the Bathurst bur is growing.
- Granny Herbicide at 45g/10L water
- G-540 GLYPHSATE at 70ml/10L water
- G-360 GLYPHOSATE at 100ml/10L water.
- GrassMate at 60ml/10L water.
- MSF600 at 1g/10L water.
- Ralid at 25ml/10L water (DO NOT use Ralid in home gardens).
- WHACK – 2,4-D 800 at 45g/10 litres water.
In all cases when spraying, add SuperWetter penetrant at 20ml/10L water to ensure thorough penetration of the herbicide into the plant.