top of page

The Successful Japanese Knotweed Herbicide Treatment Programs


We can provide an initial consultation to advise on best eradication or control methods most suited to your property..

Call us on 085 1699 592 to arrange a time that best suits your needs


All our work follows current guidelines set out by recognised experts in the industry such as the Environment Agency, Knotweed Code of Practice (2013), The National Parks and Wildlife Service (NPWS) and Invasive Species Ireland, the information published by these bodies is constantly changing therefore it is very important to stay informed and remain up to date on current Best Practice Guidelines. 


For some construction/development site`s we may need to apply for an Invasive Species Transportation Licence from National Parks and Wildlife Service (NPWS).


Optimum time of Herbicide application is late season (Mid to late September), however an early season application maybe required in year 1 to assist with access for the late season treatment.

Japanese knotweed herbicide treatment system

We can offer a best practice Japanese knotweed treatment and removal solution. Our aim is to minimise the impact of any herbicide treatment at your property. We are always trying to implement Integrated Pest Management principles (IPM) They include the following practices: prevention and/or suppression of harmful organisms/High Invasive Plants, monitoring of harmful organisms, application of appropriate plant protection (Herbicide) measures, use of sustainable biological, physical or other non-chemical methods, use of pesticides that are as specific as possible for the target plant/pest

Care is taken to apply herbicide in the correct way and the right time and rate to ensure Knotweed plants are killed completely.


Step 1. Foliage spray

This herbicide foliar spray can reach all parts of the Japanese knotweed foliage. Herbicide spray methods are applied using a Knap-sack back-pack or hand-held unit set at  ~ 1 bar of pressure and fitted with an even flat fan nozzle for a coarse droplet size to minimise drift.


Foliar spray after flowering:

This is the optimum time for spraying when the racemes or 'flowers' start to fade in late summer/autumn. This is because plants are nearing dormancy and important sugars from the plant leaves are returned to the rhizomes for energy during the winter period. This downward flow helps carry the chemical back down through the Phloem vessals into the root system and therefore aids the herbicide in reaching the tips of the root network therefore killing the plant as opposed to weaking or allowing the plant to enter a dormant stage.

Note: we always make sure that no nearby plants are herbicide drift.


On some site if applicable we carry out 2 - 3 foliar sprays. The first spray is in late May/early June and then we repeat on any re-growth that grows to 1.5 m later on in the season, Next we may apply a foliar spray  when the plants have past the flowering stage.


Step 2. Stem injection

This step is best suited to Knotweed stands near waterways or when Knotweed is growing in among expensive plants.

The stem is  injected  with a measured dosage of an Amenity Herbicide that delivers a calibrated dose directly into the bottom nodes of the plants stem, ensuring the herbicide is delivered to the root system (rhizome). Care is taken to avoid herbicide overdose which may cause the Knotweed to enter a stage of dormancy as opposed to being killed completely.


Step 3. Hand sponge

Ideal for small areas that are infested with Knotweed, where the Japanese Knotweed may be starting to grow in among borders and shrubs/trees. 


The above treatments when carried out following best practice guidelines have proved to be very successful and have shown to give very high success rates, however it is labour intensive and should be carried out by certified & experienced people.  Not all sites need a combination of all 3 of the above methods.



Knotweed Control Ireland are currently carrying out our own research some of our work studies focus on the following:

Bio-herbicide specific to Knotweed plant Spp.

Herbicide Kill rates on re-growth of varying heights.

How to determine the age class of Knotweed stands.

Bund construction: Height & Maintenance Innovation.

Re-growth rate of different Rhizome fragment size



bottom of page