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Knotweed Treatment Options
Eradicating knotweed can be a challenging problem. It can take years to completely remove an infestation and expose you to costly consequences due to current legislation.
To mitigate risks you should seek the services of a company specialising in domestic or commercial knotweed eradication to guarantee removal and, to avoid legal complications from future occupiers and affected neighbours.
Costs for knotweed removal are subject to a number of factors. For example; the area of land to be treated and the location or intended use of land, the maturity of growth and the length of time available for removal.
In most cases, simple herbicide or electrical treatments can be used to resolve knotweed problems. In the event of land being used for development, excavation may be required.
Solutions range from full excavation and disposal, electrolyte or chemical treatment to partial excavation and use of root barrier membranes. A rough outline of costs is provided in the table below.
If you are concerned about having an invasive plant species on your property, send us a picture and we'll let you know what you have and how best to treat it.
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Chemical Treatment - treatment period - 24-48 months
Special herbicides can be used during two to four growing seasons.
Depending on the size of plants, season and prevailing weather, chemical treatments can involve stem injection, root injection, cut stem treatment or spraying.
This solution should only be undertaken by fully qualified and experienced personnel; this is often the cheapest treatment option. For quicker solutions we can provide alternative methods of control and eradication.
Herbicide treatment periods can also be reduced by using a number of methods that can challenge the proliferation of rhizomes.
Beware of unscrupulous contractors who claim that knotweed can be eradicated using herbicides within a single growing season.
Various sources of guidance and advice from professional bodies and regulators, warn of spurious claims to quickly eradicate knotweed.
There are no products or commercially available chemicals that will, eradicate mature knotweed growth in a single season.
Organic - treatment period - 12-18 months
Organically treats invasive weeds such as Giant hogweed, Himalayan balsam, Japanese knotweed, and Rhododendron e.c.t. (full list of Irish invasive weeds).
Especially useful for ecologically sensitive sites and areas where other non-invasive plants need to by protected. Also suitable for water treatment areas, where chemical treatments are not an option. Infested areas can be treated by targeting each plant individually using Japanese Knotweed Killers unique electrical treatment process.
This treatment has been developed in the last few years and is becoming the treatment of choice for many developers and local government bodies.
Bunds and Herbicide - treatment period - 24-48 months
On large development sites knotweed infested areas of land can be moved to specified treatment bunds.
This method can release areas to be developed by relocating contaminated material to site areas where treatment can be applied as part of a herbicide programme.
Minimal Dig and Herbicide - treatment period - 12-24 months
This solution removes the most vigorous and hard to treat areas of knotweed plants. The remaining material can then be dealt with using a variety of soil sorting and herbicide application techniques.
Capping - treatment period - instant
This method encapsulates some or all of the Japanese knotweed growth within or under a specialist root barrier membrane. This barrier is of very high puncture resistance and is robust enough to withstand cracks or tears from most spoil materials. This process can provide instant eradication of Japanese knotweed from many sites.
On-site burial - treatment period - instant
On-site burial is another instant Japanese knotweed eradication method. This involves the creation of a burial cell that holds the excavated knotweed waste. This technique is often best suited to areas where there are no deep groundworks or services planned – e.g. car parks or public open spaces.
Screening and Sorting & Incineration - treatment period - instant
Volumes of knotweed waste can be significantly reduced by separating rhizome (root) material from affected soil. This can be achieved using a variety of screening and sorting operations using a selection of resources, including mechanical screens.
We can also incinerate contaminated material on site.
Different techniques are more effective depending on the volume of knotweed and type of infested soils to be treated. On larger sites the process may require an Environmental Permit.
Excavation and Removal - treatment period - instant
Excavation of Japanese knotweed and removal of wastes to a landfill site is a frequent option where time and space don’t allow other treatment strategies.
Guidelines suggest excavation of Japanese knotweed should be within a seven metre area around plants and to a depth of three metres. However, by carefully managing the knotweed excavation process, our experts can help reduce volumes of waste often resulting in volume savings by as much as 50-90%.
Many invasive plant species fall under the classification of controlled waste, so it is essential that contaminated material is disposed of at licensed waste facilities.
Biological Control - treatment period - unknown
In invasive species management, biological control involves the introduction of a “pest” species that will attack and control, but not necessarily kill, a target “host” species.
Host-specificity is key to successful biological control and can be very difficult to identify and achieve. If an introduced pest species affects organisms other than the target host, then valuable native species and habitats can be put at risk.
It can also be difficult to determine laboratory and field trial effects of introduced pests on the target species in the wild.
Trials involving biological control techniques are ongoing in many countries. Although no conclusions have been reached with regard to knotweed, it is unlikely that legislation will change to Japanese knotweed to spread. Knotweed will likely remain a significant problem on development sites and at existing commercial and residential properties for the foreseeable future.
Japanese Knotweed Risk Categories (from RICS Guidance)
Category Descriptors
1. Japanese knotweed is within 7 metres of a habitable space, conservatory and/or garage, either within the boundaries of this property or in a neighbouring property or space;and/or Japanese knotweed is causing serious damage to outbuildings, associated structures, drains, paths, boundary walls and fences and so on.Further investigations by an appropriately qualified and/or experienced person are required.
2. Although Japanese knotweed is present within the boundaries of the property, it is more than 7 metres from a habitable space, conservatory, and/or garage. If there is damage to outbuildings, associated structures, paths and boundary walls and fences, it is minor. Further investigations by an appropriately qualified and/or experienced person are required.
3. Japanese knotweed was not seen within the boundaries of this property, but it was seen on a neighbouring property or land. Here, it was within 7 metres of the boundary, but more than 7 metres away from habitable spaces, conservatory and/or garage of the subject property.
4. Japanese knotweed was not seen on this property, but it can be seen on a neighbouring property or land where more than 7 metres away from the boundary.
Japanese knotweed can be a serious problem for home owners. There are no quick-fix herbicide treatments to ensure immediate Japanese knotweed eradication.
How Much Does Japanese Knotweed Removal Cost?
Attempting to remove knotweed yourself can be a high risk strategy. Japanese knotweed can cause significant risk to property, which can adversely affect property values (in some cases reducing property value by over 20%). Lenders and insurance companies will require formal documentation and proof that remedial work is supported by appropriate guarantees. Property owners take a significant gamble if work is not carried-out by qualified experts.
The chart below estimates the cost of knotweed treatment options.
