There are a variety of options that can be used to eradicate Japanese Knotweed, but which is best for you and when should you start?
Determining which eradication option(s) to use depends on a variety of factors not least the amount of time there is to deal with the problem. Regardless of your ultimate choice, some Japanese Knotweed Golden Rules ALWAYS apply:
- Ensure that you use a competent experienced company.
- Doing little about the problem and leaving it until the last minute, particularly on a development site reduces the number of options and can increase the cost of eradication.
- If you see Japanese Knotweed working its way across your neighbours land if it is already within 7 metres of your boundary it may have already worked its way underground onto your land.
- The sooner “Japanese Knotweed Removal Ltd” are contacted and can survey the site then we can advise you of the options available, the associated costs and the various time scales.
Eradication of Japanese Knotweed by treating the plant with a number or appropriative specialised herbicides.
Foliar method.
Spraying a fine mist of appropriate specialised herbicide over the leaf of the knotweed plant using trained operatives with specialised equipment. The plant absorbs the herbicide and it works its way down into the rhizome or root system. Several applications are required per season in order to effectively control Japanese Knotweed.
This method is suitable for small and large swathes of knot weed that are not too near water courses or other sensitive plants. Spraying takes place from April to October depending on the growing conditions. Control usually takes at least two growing seasons.
Stem injection
Injecting a mix of appropriate herbicides directly into the stems of the Japanese Knotweed plant using specialist equipment. This method is labour intensive but allows the herbicide to get to the knotweed rhizome quicker and speed up the eradication process. Stem injection also protects nearby plants and avoids water courses. Duration 18 – 24 months.
It is important that the herbicide is transferred to the Rhizome or root system to gradually control the plant. Several applications are required (April - October) taking care not to over dose with herbicide which could force the knotweed into dormancy and pro long the treatment program.
Effective Japanese Knotweed eradication can be achieved usually after a few growing seasons. Control by means of herbicide applications is by far the most cost effective method but does require more time than the other methods. However the savings compared to removal or relocating the plant and contaminated soil are substantial.
The process can be speeded up by disturbing the soil to break up the rhizome and stimulate its growth and encouraging the knotweed plant to produce additional stems and leaves. Increasing rhizome activity can be an asset during the treatment cycle as it increases surface area or number of stems allowing more herbicide onto the leaves or into the stems and increase the amount of herbicide getting to the rhizome bringing control eradication nearer.
For sites that have Japanese Knotweed where there is building work already taking place the following eradication options also apply
In the event you can postpone the work and put construction traffic on hold you can eradicate the knotweed chemically in situ until the knotweed has been eradicated by several applications of the appropriate herbicide. Treating with herbicides takes longer but is substantially cheaper. Digging out and removing Japanese Knotweed to a licensed site involves more labour and resources, increases costs but can be quicker.
Are the infected locations on areas of the site that is to be built on?
If yes, the knotweed should be dug out and a removed to an area of the site that is not to be built on. The removed knotweed will have to be chemically treated on site and that area of the site isolated from the rest of the site until the treatment program has been completed. If you do not have available space and cannot delay the build then you will have to dig out the infested area and remove the controlled waste and soil from site to an approved licensed site using an approved licensed contractor.
Relocate contaminated soil and plants on site and treat with herbicide.
In some locations e.g. building sites, it may be possible, by means of a simple controlled move to remove the plants and the infected soil to a non sensitive location on the site where building work will not be taking place in the medium term and continue to treat the plants in a quarantined fenced off location. This allows work to carry on the rest of the site. The Japanese Knotweed stands can be scrapped and moved to a new location with the soil being spread onto a root barrier membrane to an optimum depth of 500 mm to increase the efficiency of the re growth and herbicide treatment. The aim is to get the rhizome to send out more shoots and treat all of the stems as they appear thereby ensuring that we are getting the optimum amount of herbicide into the rhizome system while it is at its most susceptible. The less soil the stem has to travel through the quicker it appears and the more herbicide we can get into the rhizome system as we treat it as it appears.
Excavation and cell burial on site that are time sensitive and little spare space.
If time is critical in the building schedule and suitable space to relocate the contaminated soil may not be an option then it may be necessary to excavate around the stands of knot weed to a distance of 7 metres away from any growth and 3 metres down. The soil produced should be deposited in a pit that has been lined with suitable membrane with the seams sealed. This area is then capped with more membrane and the seams welded tight. This cell must then be covered by uncontaminated soil to a depth of at least 2 m. The location of this cell should not be below any planned buildings but below open space.
Alternatively the contaminated soil can be buried at least 5 m below the soil surface and covered with clean fresh soil. It is recommended that the contaminated soil is not buried underneath any area that will be subject to piling or building – underneath car parks and open spaces are preferred options.
Excavation and removal from the site for disposal to a licensed landfill site.
If time is critical and no available space on the site to relocate the contaminated soil or bury the soil then the only option is to dig out and transport the contaminated soil from the site.
The infected are must be excavated and loaded into suitable vehicles from a contractor who holds the correct waste carriers licence. The loading must be carefully monitored and supervised. The costs associated with this method are substantial and the control demanding. The disposal site must be licensed to accept and process the contaminated waste. In addition to paying to remove contaminated waste from the site there may be an additional cost purchasing and transporting in infill soil material to fill the space created by digging out the land fill.
Japanese Knotweed Removal Ltd will produce a taylor made Japanese Knot weed treatment program that reflects the characteristics of the site, the time table of the building program that can keep costs down and allow development to continue.
Excavation, re-location.
The above methods plus the use of membranes and a program of appropriate herbicide treatments can be combined in a variety of ways to minimise the disruption on the site, the environmental impact, increase effectiveness and reduce costs
Training & Monitoring
Japanese Knotweed Removal Ltd can also carry out training for site personnel to ensure that any work that can be carried out by the client is carried out correctly and according to the Japanese Knotweed management plan
Price Comparisons
Sites that have cancelled or postponed the planned building works. Depending on a number of variable factors the price to treat sites varies substantially. Herbicide treatment options are usually 75 – 50 % cheaper than programs that involve moving the Japanese Knotweed and soil about the site or even away from the site.
With many building projects on hold at the moment now is the very time for landowners to review their land bank – projects and ascertain if there are Japanese Knotweed concerns and start to implement programs to address these problems in the most economic way. Successful treatment will allow you to proceed with your building program without any fear of delays or additional expense. Ignoring any Japanese Knotweed problem is a false economy and delays will usually substantially increase costs.
Japanese Knotweed Management plans J.K.M.P's
The environment Agency has made the above plan to be a major part of their code of practice in the treatment of Japanese Knotweed and place great emphasis on contractors adhering to their code of practice.
Japanese Knotweed Removal Ltd can produce a comprehensive but straight forward JKMP that serves as a record of the presence of any JK on the site, the proposed treatment program and a record of the treatments carried out. The JKMP allows all parties on site to be aware of the collective and individual responsibility in regard to the control and eradication of JK and the consequences of ignoring site protocols etc.
We can also provide a monitoring site service and carry out tool box talks on site to contractors in addition to executing the JKMP.
JKMP produced by Japanese Knotweed removal Ltd in response to enquiries from persons involved in the sale or purchase of residential properties can act as a letter of comfort when combined with a letter of commitment from the client to implement the plan. The receipt of these documents by the parties with an involvement in the transaction can remove many barriers and objections allowing the transaction to proceed safe in the knowledge that the site / property will have the Japanese Knotweed problem addressed.
