Gorse (Ulex europaeus)

Provided by Dow AgroSciences

Gorse is a spine bearing, nitrogen fixing bush. Originally from southern Europe, gorse is now easily New Zealand’s most widespread and problematic brushweed. One of the key factors that makes gorse such a successful immigrant is its ability to tolerate a wide range of climatic and soil conditions. In addition, an average gorse bush will produce 8000 seeds per year, many of which will survive for well over 30 years in the soil!

Controlling gorse requires a stringent management plan. Control will only be successful in the long term with a combination of several farm management practices. Herbicides are the preferred tool for the initial control of gorse. To reduce variability when using herbicides, it is important to understand the seasonal growth pattern of gorse in your area and which herbicide is the most appropriate for your conditions.

Control

In most regions, gorse will flower continually for many months but peak flowering occurs in spring each year, with pod development and ‘soft’ growth occurring a few weeks later. Gorse is most easily and effectively controlled with herbicides when soft growth is present. Regional and climatic variations dictate how much ‘soft’ growth develops and how long this growth remains ‘soft’. Gorse usually starts to ‘harden off’ after February.

Dow Agro Sciences produce three very effective gorse herbicides - Grazon*, Tordon* Brushkiller and Veto*. Grazon* and Tordon* Brushkiller are the preferred herbicides to use in pastoral situations as they do not damage grasses, although clover will be temporarily removed from the sward.  This is important as the removal of grass during spraying only increases the opportunity for both gorse and broadleaf weed seedlings to establish, further reducing pasture quality. Both products can be applied using ground equipment or from the air. Veto* is suitable for areas of solid gorse that need opening up before following up with grass friendly products, or where gorse is present with scrub or blackberry.

During hard conditions (slashed/dry/salty/cold), Tordon* Brushkiller plus Boost* Penetrant will produce the most reliable and cost effective result.The addition of a penetrant in these situations is very important, as it decreases the variability in control. If in doubt as to the growth stage or condition of the gorse, always add Boost* Penetrant to your spray mix. Grazon* is ideal for spring and early summer spraying of smaller gorse.

Water rates are very important when using herbicides on gorse. Large gorse needs a higher volume of spray mix, as these bushes have large surface areas to treat. It is not recommended to burn treated gorse, as this damages pasture and encourages dormant gorse seeds to germinate. Follow up treatments will almost certainly be required after burning.

When trying to control gorse on your property, it is very important to budget for and to plan your strategy. Scattered bushes should be controlled as soon as possible, as smaller bushes require less spray and gorse spreads very quickly. Some new seedling growth and some follow up must be expected, and plans should include treatment of this 12-18 months after the first treatment. It is more effectiveto treat a smaller area, and ensure you can meet the follow up costs, than do larger areas and not follow up.

It is just as important to increase soil fertility and maybe even re-seed after spraying. Large blocks should be fenced so grazing can be controlled. This will encourage a dense, competitive, higher quality pasture sward, which will in turn decrease establishment of noxious weeds. On steep or water logged country, grazing management should ensure that pugging is kept to a minimum. Pasture which is "opened up" (i.e. pugged, by stock during grazing) is more likely to encourage establishment of weed seedlings.

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