Eradication of Japanese Knotweed

Japanese knotweed is not harmful for humans but still, it has to be eradicated because of its invasive nature. If the weed grows on concrete walls, tarmac or foundation, it can cause damage to the structure where it is growing.

It is quite difficult to eliminate Japanese knotweed from an area, because this plant has a widespread root system. It can spread as far as 7 meters in length and bury 3 meters deep into the soil.

Moreover, the plant can survive in all types of soil and can tolerate a very cold weather condition. Therefore, you may have to use a number of different techniques for its total eradication. A few effective methods for Japanese knotweed control are discussed further:

This involves cutting the portion of the plant which is above the ground. Its stem tends to regenerate itself again and again within a short span of time. It needs repeated trimming of new shoots coming out of the ground frequently. After several rounds of cutting, the roots of the plant become weak and the entire patch of the weed can be eliminated.

This is not a very popular choice because even if a small portion of the root of the plant is left behind, it can grow with a thicker density on the soil surface. So, it is suitable only for the Japanese bamboo plants which have started growing only in the recent times and its root system has not yet been firmly established in the soil.

This is the most widely used method for controlling Japanese knotweed, because it gives faster results. However, regular weed killers cannot be used for this purpose as it will take a long time before you can be sure whether the weed has been eliminated completely or not.

Glyphosate-based herbicides are the most suitable choice available with you. This active ingredient suppresses the action of an enzyme which is involved with the synthesis of amino acids that are essential for growth and survival of the plant.

When it is sprayed on the plants, the systemic action of glyphosate enables it to permeate into the entire network of the roots and destroy them. Once the plant dies, remove its surface growth from the soil and keep it in an isolated area for drying. Later on, destroy the dried plants by burning.

Make sure that the depth of this dug out area is at least 2 meters, as these are quite deep-rooted plants. Pull each plant out of the soil with the crown and the rhizomes and spread it over a plastic sheet and let it dry up.

These uprooted plants should not be exposed to moisture at all. When they dry thoroughly, incinerate them within the infested area. Even after uprooting the plant along with its entire roots, there is a chance of regrowth in the same area. So, you must keep a close watch on this area for the next five years.

Those who want to avoid use of strong chemicals for this task have a safer option known as soil steam sterilization. Here, hot steam is injected into the soil of contaminated site, which when enters the plant cells, destroys them and the plants cannot survive.

Research studies have found that introducing Mycosphaerella leaf spot fungus on the weeds can control their unwanted growth. Similarly, Aphalara itadori, a plant-feeding insect native to Japan has shown promising results. However, you cannot expect instant results from these two biocontrol agents.

For a successful Japanese knotweed eradication, the waste plant materials should be handled with great care and prevent reinfestation. If you are not burning them, then you should bury them deep into the ground in a licensed landfill in your area.

After the task is over, all the tools, instruments, the clothes and shoes that were used at the time of Japanese knotweed removal should be washed thoroughly at the site, as plant fragments attached to these items can contaminate soil in other areas.