Pest Plant Programmes
Pest plant of the month - January
German Ivy
German Ivy (Delairea odorata) has recently been found in Bluff. It looks similar to common Ivy, but is actually quite different. German Ivy is a scrambling vine that grows up to three metres in height. The stems are thin and quite weak. The leaves are a glossy green and "ivy-shaped". They are soft and thin with no hairs and are clammy to touch. German Ivy has yellow, ragwort-like, flowers from May to October. German Ivy also has fluffy seeds that are distributed by the wind.
It is very invasive and will grow in a wide range of habitats, including coastal areas, lowland forest margins, shrubland, roadsides, quarries, and swamps. German Ivy will smother any small trees and lower vegetation. There is an eradication programme for German Ivy so if you see it please call us. We will remove it at no additional cost.
Gunnera is seen as an environmental pest. It spreads aggressively in coastal and damp areas where it can displace native species. Its seed is distributed by birds and is therefore hard to contain once it gets established. Over the last 20 years, Gunnera has started to spread out from areas where it has been planted on Stewart Island. An eradication programme for Gunnera on Stewart Island has begun. If you see any Gunnera on Stewart Island please contact us.
Ragwort can significantly reduce pasture production once it has established. It is also toxic to many animals including humans, though sheep seem to be able to tolerate it in moderate amounts. It is also invasive in riverbeds, disturbed forest, shrubland and coastal areas.
As ragwort is so widespread in Southland our aims are to prevent its spread onto properties that are clear of it, provide advice to landholders on the best control methods, and to increase the distribution of biological control agents to help reduce its impacts and distribution. Landholders are required to keep their boundaries 50m clear of ragwort to slow its spread from affected properties to unaffected ones.
Gorse and Broom growing in urban areas have been identified as a concern to the Southland community. Environment Southland operates inspections in urban areas to:
- minimise Gorse and Broom in urban areas
- reduce the medium and severe infestations over time to minor ones
- continue to improve roadside and public land issues
The inspection programme is usually carried out from the roadside without going on to an individual’s property. For any minor gorse and broom issues the landholder is sent a letter asking them to destroy their plants within a specified time, usually 8 months. For medium and severe infestations a Notice of Direction is issued requiring action within one month.
Territorial local authorities (i.e. Southland District Council, Gore District Council or Invercargill City Council) are alerted to any issues that may be present, for example on road verges, and asked for these to be included into their work programmes.
For rural areas the rules in the RPMS require that boundaries and watercourses be kept clear for a minimum of 10m. Currently, we do not have the resources to inspect all rural areas and watercourses for gorse and broom. However, we will respond to any enquiries or complaints we receive about them.
Nodding Thistle is an aggressive thistle that is difficult to remove once established. It has spiny foliage which prevents grazing by stock. Single rosettes can occupy an area greater than one metre and large infestations can seriously reduce the stock carrying capacity of affected pasture.
Nodding Thistle has not yet spread to all suitable habitats in the region. For this reason, it is important that new infestations are controlled as soon as possible. The Nodding Thistle programme aims to contain its distribution and abundance, as well as raise public awareness about the seriousness of this pest.
While Nodding Thistle is predominantly an agricultural weed, it is also found in riverbeds. Currently its distribution in rivers is limited. Each year Environment Southland uses contractors to locate and destroy Nodding Thistle where it is found in a river system. This programme is partly funded by Land Information New Zealand which manages the riverbeds on behalf of the Crown.
Old Man's Beard (Clematis vitalba) is a temperate, deciduous, woody vine which invades disturbed areas and creates a dense canopy up to 7000 stems per hectare. Old Man's Beard inhabits and potentially damages remnant native forests, river beds, urban areas and plantation forests.
The Old Man's Beard eradication programme started in 2001 by the Department of Conservation and due to lack of funds, it was passed to Environment Southland in 2008. The programme started with 64 sites, the number of sites has increased to 95 as more sites are found by the public each year with our publicity campaigns. If you have seen any Old Man's Beard please call us and let us know. We will come and remove it for you at no additional cost.
Purple Loosestrife
Purple Loosestrife is an erect, hairy, summer-green, perennial herb, which grows in damp areas such as the margins of wetlands, lakesides, streams, ditches and riverbeds. It can form large impenetrable stands that block out all other species. Purple Loosestrife destroys wetland habitat and can cause blockages which can contribute to flooding.
Purple Loosestrife grows to 1-2 metres (occasionally 3 metres) high. It has many branched stems. The leaves are narrow and the flower head forms spikes 20-25 cm long that are densely hairy with many purple-magenta flowers. Flowers are seen from December to February. There is an eradication programme for Purple Loosestrife. If you have seen any please don’t hesitate to call. We will come and remove it at no additional cost.
Smilax (Asparagus asparagoides) is a scrambling vine that smothers trees and low stature plants, climbing up to three metres high. The leaves are small, oval and thin to the touch. Small, greenish-white flowers are produced in July and August followed by red berries. Simlax produces tubers near the surface which allows it to re sprout after the stems have been cut or sprayed. These tubers make Smilax hard to eradicate once established.
There are very few known sites of Smilax in Southland, all these sites are closely monitored. We are hopeful that this species is nearly eradicated from Southland. If you have seen any Smilax please call us and let us know. We will come and remove it for you at no additional cost.
German Ivy
German Ivy (Delairea odorata) has recently been found in Bluff. It looks similar to common Ivy, but is actually quite different. German Ivy is a scrambling vine that grows up to three metres in height. The stems are thin and quite weak. The leaves are a glossy green and "ivy-shaped". They are soft and thin with no hairs and are clammy to touch. German Ivy has yellow, ragwort-like, flowers from May to October. German Ivy also has fluffy seeds that are distributed by the wind.
It is very invasive and will grow in a wide range of habitats, including coastal areas, lowland forest margins, shrubland, roadsides, quarries, and swamps. German Ivy will smother any small trees and lower vegetation. There is an eradication programme for German Ivy so if you see it please call us. We will remove it at no additional cost.
Biological control (or "biocontrol") involves using the natural enemies of a pest to help reduce the damage it causes. Biocontrol reduces the population density or impact of a specific pest, making it less abundant or less damaging than it would otherwise be. In Southland, biocontrol of weeds has been in use since 1984, with 28 different biocontrol agents released in the region (25 insects, 2 mites and one fungus).
How safe are biocontrol agents?
All potential biocontrol agents undergo rigorous testing before applications to the Environmental Risk Management Authority are made to bring them into New Zealand. Only those organisms which feed specifically on their targeted host plant are released. Much of the biocontrol research done in New Zealand is carried out by Landcare Research. Click here to read more about biocontrol in New Zealand.
Some advantages of biocontrol include:
- Biocontrol agents are specific to their host plant so other plants are not affected.
- Biocontrol agents actively seek out their host plant and will damage weeds in areas that may not be known about.
- Once populations become established, biocontrol agents are self-sufficient and require no human supervision.
- Biocontrol agents are not constrained by property boundaries.
- Over time, biocontrol can be more cost-effective than mechanical or chemical control methods.
- Biocontrol is compatible with organic agriculture and is viewed positively by overseas markets.
The Biological Control of Weeds Programme in Southland is administered by Environment Southland. There is a strong focus on biocontrol agents which specifically target broom, ragwort and thistles as these weeds are widespread and abundant throughout the region. The programme involves monitoring and distributing existing biocontrol agents in Southland, and coordinating the release of new agents when they become available. Biocontrol agents will eventually spread to wherever their host plants are present. By harvesting and releasing agents from established populations we can speed up this natural dispersal. Biocontrol agents are wholly reliant on their host plant and will not eliminate every last plant. However, biocontrol agents can reduce the impact of their host plants to a manageable level, freeing up resources to tackle other invasive weeds.
Biocontrol agents are available free to Southlanders through the Biological Control of Weeds Programme. Their availability is determined by the amount of agents ready for harvesting, and the suitability of potential release sites. Biocontrol may be compatible with using herbicides depending on the agent and when the herbicides are used.
To find out more about specific biocontrol agents in Southland follow the links below:
Environment Southland is the brand name of Southland Regional Council.