Keep gorse and Scotch broom from affecting nearby land
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|Production threat||Environmental threat||Public threat|
Gorse is a deep-rooted woody perennial that can grow up to 4m high.
Scotch broom is a deciduous shrub which grows up to 2.5m tall. It is most recognisable by its distinctive upright green, woody stems that are five-ribbed and hairless. Scotch broom normally grows in areas of high rainfall and can tolerate a wide range of soil conditions.
Gorse is widespread throughout the Waikato region, reducing the area available for grazing by livestock on pasture land and invading naturally open spaces. The foliage of gorse can become dry, making gorse stands susceptible to fire. Gorse’s ability to fix nitrogen in the soil can lead to adverse effects on water quality. Gorse is widespread throughout the Waikato, affecting pasture, roadside verges, scrub land, forest margins and coastal habitats.
Scotch broom is an aggressive pest plant, which is unpalatable to stock and will reduce stocking rates. It shades out pasture and inhibits its growth. Large thickets of broom can also prevent stock from getting at any grass surviving underneath. It is an agricultural pest plant but also causes problems in forestry, wastelands, along road and rail sides, braided rivers and protected natural areas. Broom is particularly a problem in the open tussock grassland of the North Island central plateau south of Tokoroa.
All landowners/occupiers in the Waikato, on complaint from an adjoining neighbour, are responsible for controlling gorse and broom within 20m of their property boundaries and are required to work with Waikato Regional Council in areas where control programmes are in place. Gorse and broom are also banned from being sold, propagated, distributed or included in commercial displays.
Many herbicides are not effective on gorse because of the shape of the ‘leaves’ and the thick cuticles on the spines, which help prevent absorption of herbicides. However, gorse can be killed using herbicides like glyphosate, metsulfuron or triclopyr/picloram mix or stump treated with picloram or glyphosate gel.
Physical control includes removing plants by hand, with machinery or by burning. It has been found that when the plants are big, cutting at the base (at flowering time) and fraying the stump causes the stump to lose moisture and generally kills the plant. As with many scrub weeds, gorse/broom soon regrows from dormant buds on stumps if shrubs are cut with chainsaws or slashers without prior herbicide treatment. Regrowth from buds can also occur after fires. The cheapest treatment for large blocks of gorse/broom may be to fence it off and wait for it to revert to native bush. On less steep land, ploughing or repeated rotary slashing can be used.
The basal treatment X-Tree® can be applied with a low pressure sprayer using solid cone nozzle or a paintbrush. Liberally treat the full circumference and at the base of the shrub or tree trunks so the spray thoroughly wets at least 2-3 times around the diameter of the lower stem or trunk including the root collar area.
A hand slasher or scrub cutter can be used on isolated bushes but if the stump is not treated immediately with a herbicide, regrowth will occur. Large areas of slashed stumps can be left to grow to 0.5m in height and then sprayed.
As mentioned, gorse can be killed using herbicides like glyphosate, metsulfuron or triclopyr/picloram mix or stump treated with picloram or glyphosate gel. Hard grazed gorse or recently slashed gorse is difficult to control because of reduced foliage to take up herbicide. Active growth is more susceptible to spraying. Your biosecurity pest plant officer can give you advice on the timing and method of application best suited to your situation.
Disclaimer: Any product names mentioned below are not an endorsement nor are they a criticism of similar products not mentioned.
|Picloram gel||Cut stump treatment.|
|Glyphosate||Spray application and cut stump treatment|
|Glyphosate gel||Cut stump treatment.|
|Metsulfuron||Spray application and cut stump treatment.|
|Triclopyr/picloram mix||Spray application and cut stump treatment.|
|Triclopyr||Spray application and cut stump treatment.|
|X-Tree ®||Basal treatment of trunk.|
|Herbicide rules will apply. You may need to notify neighbours if spraying. The Waikato Regional Plan explains the agrichemical (herbicides) use rule in section 6.2|
After initial control, it’s important to:
Six separate biological control agents for gorse have been released within the Waikato region. The most successful of these has been gorse spider mite. Four broom agents have been released – the broom seed beetle, broom twig miner, broom gall mite and broom psyllid.
Landcare Research runs a national biological control programme. Waikato Regional Council supports this programme and maintains a local biological control programme for the Waikato region. For more information on biocontrol agents visit www.landcareresearch.co.nz.
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