Japanese Knotweed

Baroness Sharples Excerpts

Monday 8th July 2013 Lords Chamber

Asked by

[Baroness Sharples]

To ask Her Majesty’s Government what progress has been made in eliminating Japanese knotweed in the United Kingdom.

[The Parliamentary Under-Secretary of State, Department for Environment, Food and Rural Affairs (Lord De Mauley)]

My Lords, we commenced a controlled release of Aphalara itadori to tackle Japanese knotweed in 2010. The signs are encouraging for the establishment of this highly specialist psyllid. Aphalara successfully overwintered but numbers remained low and so additional releases were made in spring 2012 and spring 2013. No non-target impacts have been observed by the programme of close monitoring.

[Baroness Sharples]

Will the psyllid really be enough to kill off this pernicious weed? There are increasing reports of wretched owners of land who have had their land affected by Japanese knotweed and have been refused mortgages. Why can we not give them natural Roundup which is unpolluted? I managed to kill off my knotweed a number of years ago.

[Lord De Mauley]

My Lords, experience from around the world has shown that biocontrol tends to take five to 10 years from the initial releases to achieve effective control. Despite poor summer weather since its release, Aphalara has shown that it can survive in small numbers and overwinter in the wild here. The question is how we can encourage it to achieve survival in larger numbers.

My noble friend mentions mortgages, and we are aware that some mortgage lenders have become reticent to lend if Japanese knotweed poses a threat to the property concerned. We have undertaken some work to estimate the impact of this. The RICS believes that recent concerns by valuers and lenders are often based on misunderstandings, and it consulted on that in 2011 in order to help valuers and mortgage lenders to understand the implications. Cornwall council has also provided guidance for mortgage lenders.

On the use of Roundup, I understand that others have also had success with it. Of course, it needs to be applied with care, and we are also looking carefully at a couple of other possible biocontrol options.