Skip to main content

Japanese Knotweed

Volume 736: debated on Wednesday 28 March 2012


Asked By

To ask Her Majesty’s Government what progress they have made in eliminating Japanese knotweed from the United Kingdom.

My Lords, we are working towards sustainable natural control of Japanese knotweed. The controlled release of the highly specialist psyllid, Aphalara itadori, is progressing well and we are nearly two years into the release phase. If successful, the psyllid should restrict the growth of Japanese knotweed, slow its capacity to spread as vigorously and enhance the effectiveness of other management effort. I regret to say that it will not eradicate this invasive plant altogether.

My Lords, perhaps in my perseverance in asking this Question over 25 years, we are actually getting somewhere. The psyllid is quite a success but are there other ways of ridding ourselves of this extremely invasive and destructive weed?

I would like to thank my noble friend for her persistence, which I think rivals the Japanese knotweed in its vigour and eradicability. Research is going on into a leaf spot fungus, which also has the capacity specifically—this is the key to biological control—to attack Japanese knotweed. Defra and the devolved Administrations are also supporting catchment scale control work on Japanese knotweed in several areas across the country.

My Lords, while waiting for this new panacea to have effect, does the Minister agree that Japanese knotweed is pretty lethal stuff and that there are virtually no powers to deal with it if one sees it in adjoining gardens or houses? Short of having to take civil action, which is pretty cumbersome—especially given the legal aid Bill—should we not have better enforcement powers? People do not know about it, and not all police forces have wildlife officers, so why not give local authorities the power to deal with it?

The noble Lord makes a very important point. Japanese knotweed is a pest and it is extremely difficult to eliminate. However, I remind the noble Lord that this House guards jealously the right of entry. I remember many debates on that issue and I am not sure that this House would be particularly happy to have people’s gardens invaded by enforcement officers in the way that he suggests.

My Lords, when I read this excellent Question of the noble Baroness, Lady Sharples, I wondered whether it was code for the knotweed growth regulation that was debilitating our economy.

As my noble friend will know, Defra has been extremely vigorous in responding to the red tape challenge. Indeed, the red tape regulatory reduction targets of this Government are being vigorously enforced. Unfortunately, we do not have a psyllid that we can apply to them.

My Lords, I am very pleased to hear of the progress on the introduction of the psyllid, which passed its scientific trials on my watch when I was a Defra Minister two years ago. I was persuaded, as I am sure the whole House will be, at how threatening the plant is. Network Rail’s permanent way, embankments and the lines themselves are threatened by knotweed and it has to deal with it at immense cost. Householders in Broxbourne, the borough in which I live, lost their £300,000 home the other day because the weed had infested their land. We cannot take this lightly. The noble Lord is right that we place a great deal of hope on the psyllid but we certainly need to make progress on its employment.

The noble Lord is absolutely right to remind us of the continuity of government. It was helpful to be able to take up where the noble Lord left off. He was right to point out that this is a serious matter, particularly for those people who find their properties affected. That is why the Government are investing a considerable amount of money in the area. The cost to the economy is £166 million per annum, which is a sizeable sum. That is why we consider it a priority to find effective control.

My Lords, is my noble friend confident that other invasive species will not be permitted to come to this country? Clearly this has been a very long-term problem and we need to make sure that we do not allow in such species in the first place.

My noble friend is absolutely right. One of the hazards of climate change is that we may find exotic plant and animal pests coming to this country. Defra is constantly on watch; Fera, our science agency, gives us advice; and we monitor plant imports with the express purpose of trying to make sure that we do not allow such an accident to happen again.

My Lords, on the saga of this weed, is Defra or any other organisation working on a solution to find an insect or animal that can destroy the weed by simply eating it?

That is exactly how the psyllid works. It is a mite-sized fly or beetle-type insect that has the capacity to suck the sap out of Japanese knotweed. This has proved to be a very effective treatment. It is a biological control; the psyllid is knotweed-specific and does not destroy other plants. This is why we are particularly pleased with the outcome of the trials that were conducted, and why we see it as the most effective way of controlling the pest.