THE MOST RECENT EDITION OF SUSTAIN MAGAZINE HAS FEATURED AN INSIGHTFUL DISCUSSION AS TO HOW THE INVASIVE WEED INDUSTRY IS RESPONDING TO A PROPOSED BIOLOGICAL METHOD OF JAPANESE KNOTWEED CONTROL -

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THIS DISCUSSION HAS SPLIT THE INDUSTRY AND H.I.S WOULD BE KEEN TO KNOW YOUR THOUGHTS, EMAIL: JAMES.TYERS@HERPETOSURE.COM

UNTANGLING THE KNOT

JAPANESE KNOTWEED, FIRST INTRODUCED INTO THE UK AS AN ORNAMENTAL PLANT, NOW PLAGUES THE ENVIRONMENT AND ITS REMOVAL CAN BE COSTLY AND TIME CONSUMING. HOWEVER, RECENT RESEARCH INTO BIOCONTROLS BY SCIENTISTS AT CABI HAVE SUGGESTED THAT A SAP-SUCKING PSYLLID INSECT (APHALARA ITADORI) COULD SUCCESSFULLY BRING JAPANESE KNOTWEED UNDER CONTROL. THE NEWS HAS RECEIVED A VERY MIXED RESPONSE FROM THOSE INVOLVED IN THE ERADICATION AND CONTROL OF THIS MOST PERNICIOUS WEED. SUSTAIN’ INVITED REPRESENTATIVES FROM THREE LEADING KNOTWEED SPECIALISTS TO DEBATE THE ISSUE: MAXIME JAY, MANAGING DIRECTOR, MUSKETEERS GROUP, CLIFFORD HARRIS, DIRECTOR, HERPETOSURE, AND NIC SEAL, DIRECTOR OF ENVIRONET CONSULTING.

MUSKETEERS: Why do you feel so strongly againstusing bio-control agents for the remediation of Japanese knotweed? Surely you must see some benefits from releasing bio-control agents?

HERPETOSURE: I am very cautious about making further changes to the UK, as the introduction of non-native species is the problem in the first place. Developers typically need to eradicate infestations –not just keep under control – so the bio-controls willnot, in many cases, be the right solution. I am concerned that the introduction of further species will potentially harm conservation in the long term ifthe new species act differently as predicted.

ENVIRONET: We have concerns about the release of other non-native species and are yet to be convinced hat this can be done safely without detriment toother species within our environment. We accept the excellent research being carried out by CABI and agree that bio-control agents may control knotweed – however Environet’s objective, particularly within a development-site scenario, is eradication which will not be achieved with bio-controls. Further more, if Aphalara itadori, or indeed any other non-native biological control agent, is released into the environment, how can we be sure that it will only feed off Japanese knotweed, and not any other species of perhaps more commercial value, such as crops, or biological value such as rare flora?

MUSKETEERS: There will always be risks associated with the introduction of foreign species into a new environment. We cannot afford to be complacent about those risks and thus we ought initially to invest in science. This is in order to understand and evaluate those risks, providing mitigation measures to palliate them so that we are able to take appropriate decisions. With regard to the works undertaken by CABI, two knotweed predators were selected out of 226 insects and fungi. The psyllid and the leaf mould were the only tested predators that did not attack other plant species. However, the predators were presented with only 79 different plants. Although we are not experts in this specific scientific area, we feel that 79 plants is not a representative sample of our natural botanic heritage and consequently further research is required before a foreign predator is released in the UK.

HERPETOSURE: The new bio-controls may eat away at the plants, but do they fully eradicate the plants? If some of the plant is left insitu, the plant will be viable in the future and therefore surely the plant will still need to be properly removed later on?

MUSKETEERS: The introduction of a knotweed predator and consequently the works undertaken by CABI has never been about Japanese knotweed ‘eradication’ (otherwise the knotweed would have disappeared from Japan a long time ago!!) but rather Japanese knotweed ‘control’. The predator will only attack the visible part of the knotweed thus weakening, but not killing, the rhizomes. Sites ear marked for development and contaminated with Japanese knotweed will still require to be adequately remediated even if the knotweed has already been affected by predators. It is not developers that will benefit from the successful introduction of predators but rather large landowners and conservationists alike. The anticipated outcome should be a slow down in the spread of Japanese knotweed.

ENVIRONET: Aphalara itadori may control knotweed but will not eradicate it. It is unlikely therefore to be the solution for knotweed-infested development sites, especially with tight construction programmes. In non-time critical situations it may provide an element of control, as would a relatively inexpensive herbicide-treatment programme. Do you not think that the environmental risks of introducing another non-native species to control one already causing havoc in the UK outweigh the benefits, especially as alternative herbicidal methods can be used effectively and safely?

MUSKETEERS: Well, let’s examine the facts. The most cost-effective technique to eradicate Japanese knotweed is a herbicide-treatment programme. DEFRA has estimated that the cost of dealing with knotweed by spraying it would be around £1.5bn. Inaddition, it was calculated using a Glyphosate-based herbicide, which is considerably cheaper than themore effective but expensive herbicides. We should consequently expect the real cost of the eradication of the knotweed to exceed well over the £1.5bn mark. Even if we kept to a £1.5bn budget, who is going to pay for this? It is obviously economically impossible to achieve. Dramatic situations require drastic actionsand the insects would enable the control of the knotweed without any cost implications. Moreover, whilst it may be appropriate to spray the knotweed in a few localised areas, we just do not know what the impact could be for releasing herbicides into the environment on a large/national scale. Although far from being ideal, the introduction ofnew species into our ecological heritage could represent an attractive economical option for the control of Japanese knotweed. Since you disapprove of the use of bio-control agents, what would you consider to be the most cost-effective and practical approach for eradicating Japanese knotweed?

ENVIRONET: For development sites with tight programmes we advocate Environet’s Xtraction method, whereby knotweed rhizome can be removed from infested soil at a fraction of the cost of ‘dig and dump’ without the use of any herbicide. For non development sites, we accept that biocontrol may be appropriate, if, and only if, it can be done without undue risk to other species within thelocal environment.

HERPETOSURE: What about a systematic approach of mass publicity to enable proper identification,followed by a county by county eradication programme? This would be long term, but more realistic, as we have the means to eradicate Japanese knotweed available today. Much knotweed is spread by human beings, so if we can put in place the right controls to prevent the spread of knotweed by people, increase identification, and put in place effective eradication strategies, we could take control of this problem starting today

MUSKETEERS: Without the introduction of bio control agents, how do you see the state of Japanese knotweed spread (along with itseconomic/environment impact) across the UK withinthe next 15 years?

ENVIRONET: Despite the efforts of many organisation stackling the knotweed problem, we believe it’s growing faster than it’s being killed. With the current economics ituation, less money is likely to be spent on knotweed treatment over the coming years so we’re sure the problem is only going to get worse. But just because the UK has a large and growing knotweed problem we caution against what might seem like a cheap solution – the full effect of bio-control agents will only become apparent after release – let’s hope we don’t then need to start looking for another bio-control agent to control the one for knotweed.

HERPETOSURE: I feel that organisation and commitment is the key to long-term success. If a Nationwide programme was developed, invasive weeds could be attacked in a methodical, co-ordinated manner and within ten years real results could be achieved. I am very in favour of new innovations, but I feel we should focus on utilising the assets we have.