If Knotweed were easy to eradicate then it wouldn’t be such a problem within the UK and with the recent introduction of anti-social behaviour orders for failing to properly deal with invasive species (including Giant Hogweed and Rhododendron Ponticum) then knowing correct procedures to treat the spread of the species is more important than ever.
Well known treatments include:-
Herbicides – Either by a sprayer, stem injected or weed wiper. Best applied during the flowering period of late summer. The sprayer operator must have relevant qualifications in the safe handling and use of pesticides and sprayer applicator. All regulations and conditions of the herbicide product label must be adhered too.
Excavation and on-site treatment – Excavating exposes the plant and roots to be treated as one. Once excavated herbicides can be sprayed, the knotweed stems can be burnt to reduce the mass of vegetation. Placing it in a bund for treatment encourages the plant to grow and makes the herbicide more effective.
On Site burial – Working in conjunction with herbicides or as a stand-alone option, the knotweed can be buried. Either within a suitable plant resistant membrane, or at a depth greater than 5m without a membrane.
Off-site disposal – Generally the quickest, simplest but most expensive option. The knotweed and surrounding soil are taken to an appropriately license disposal facility to be dealt with. Any excavation of knotweed must remove all viable plant material this means that you can end up with quite a large excavation.
As with any of the treatments it’s imperative to maintain a “containment approach” to nullify the spread of the knotweed. Fence off the area you’re working in, have only one entrance into the area with appropriate cleaning facilities at hand. For vehicles this would include power washers to remove mud and plant material from wheels or tracks. Workers will need brushes to clean down boots and clothing. Everything which gets washed off then needs to be suitably handled to prevent spread.
Everything you wanted to know about Japanese Knotweed but were afraid to ask
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