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Japanese Knotweed

Volume 797: debated on Thursday 16 May 2019


Asked by

To ask Her Majesty’s Government what recent steps they have taken to eradicate Japanese knotweed.

My Lords, we are trialling biocontrol methods to control Japanese knotweed. The Centre for Agriculture and Bioscience International is working to establish the highly specific psyllid, Aphalara itadori, into the United Kingdom. This summer, a population of a more climatically suitable psyllid from Japan will be brought here. It is hoped that this will be the key to unlocking the potential of this agent to reduce the effort and cost of managing Japanese knotweed and its invasive capacity.

My Lords, it is 30 years since Lady Sharples started asking questions about Japanese knotweed, and about 12 or 15 since I joined her, but all we get is the same answer every time: that this wonderful psyllid, Aphalara, will come galloping over the horizon and solve everything. It is absolutely clear that the problem of Japanese knotweed is getting worse and worse and causing more and more problems, and it is simply not being tackled. Do the Government agree that two things need doing? First, owners of land need to be put under a legal obligation to eradicate Japanese knotweed, and allowing it to grow should be an offence. Secondly, when transactions or contracts are made relating to land that has Japanese knotweed on it, or when people walk on it and may spread it, they should be notified that this dreadful, awful weed exists or has recently existed on that land.

My Lords, trials often take longer than we wish, but I assure the noble Lord that we are collaborating with Canada, because it has a similar problem, and with experts across Europe and the United States. I agree: it is frustrating that the psyllid has not established as we wished. We are working on another form of control, which is also under evaluation: a mycoherbicide. This is all part of using the science. I agree with the noble Lord that it is very invasive. That is why I will read some of the advice in the Science and Technology Committee report that came out this morning. We need to attend to this. The problem with the noble Lord’s first point is that, if someone fly-tips spoil with elements of Japanese knotweed, will the landowner really be required to remove that fly-tip? That is the problem if you make it a legal liability on the landowner to remove it.

My Lords, could my noble friend have a word or two with the highways agency? It has recently been spraying all over the place to kill insects. The effects of that are rather dubious, apart from keeping our car windscreens rather cleaner. But there is knotweed, and other noxious weeds which are surely covered by the Weeds Act, all the way along the sides of our motorways. Why not get it to do something?

We are strongly of the view that we need to look after our pollinators and insects, so we should not cut verges unless it is necessary for safety. This is certainly an issue I will take up with my Department for Transport colleagues, but I know that both Highways England and Network Rail are conscious of their responsibilities. Indeed, there have been cases in which Network Rail has been required to attend to Japanese knotweed. This is a real problem, and I encourage landowners to attend to it.

My Lords, we are all indebted to the noble Lord for continuing to raise this issue. It is very serious, and many thousands of people have difficulty selling their houses because of the existence of Japanese knotweed. We all hope the bio approach works, but it will take several years. The Government cannot deal with it; it remains with the local authorities to handle it. Can they step up their efforts and advice on the herbicide approach to tackle the problem today and fill the gap before the bio approach comes in?

The noble Lord raises something really important. A very good practice manual has been published as part of a RAPID LIFE project, showing the varying ways in which this can be dealt with. They all have their issues because of the rhizome’s ability to continue, even dormant, for 20 years. Glyphosate, properly used by trained people—I emphasise “properly”—can kill Japanese knotweed in about two or three years. Biocontrol would obviously be preferable for reducing the aggressiveness of the growth, but there is a whole range of issues. I am happy to share the manual with the noble Lord.

My Lords, I draw attention to my interests in the register. Of course, knotweed is not the only invasive alien species around. This is Invasive Species Week; indeed, the Minister has been seen in the newspapers digging up skunk cabbages. Can he confirm that the Government are intensifying their efforts to combat invasive alien species in general, and in particular the grey squirrel, which is doing so much, so distressingly, to kill our broad-leaf trees?

My Lords, it is indeed Invasive Species Week, and I would very much have enjoyed it if your Lordships had been with me in a ditch in Kent digging up American skunk cabbage. This is being undertaken by volunteers working in local action groups. Anyone who googles “Invasive Species Week” will find all the places they can go to help and work with the teams. Grey squirrels are one of the reasons people are not planting trees. If we do not find ways of controlling the grey squirrel, we will not have the treescape for future generations. That is why we think the investment in fertility research—I know the noble Earl has been working hard on this—that will make the grey squirrel infertile has a lot of prospects and will be a way of helping to control this very invasive species.