insect fights knotweed

[artdemole]

on bbc news web page-also in the news-science+ environment .Japanese insect to be introduced to tackle knotweed problem. Will this insect itself turn into another problem attacking other plants and insects

[Stinky Bob]

It has been trialled for a while now against other plants (the intial proposal was against 79 other plants), you would hope that the days are gone when a biocontrol was released into the wild without rigourous testing beforehand.

[pressld2]

I heard this on the Today programme this morning and my immediate thought was it's a bad idea. The newsreader confidently asserted that they "only eat Japanese knotweed". That may be true when JKW is in plentiful supply but insects can evolve incredibly fast when they need to.

Dave P.

[Jason Green]

Hello all,

I was just about to post this myself! When running a quick Google search on the Psyllid I came across a near-identical BBC report from 2008 when the plan was submitted to the Government for approval... BBC NEWS | Science & Environment | Predators could be superweed fix - and a subsequent WAB thread from the same year... Japanese Knotweed versus Aphalara itadori

I don't forsee a non-native Vs. native, Harlequin-style problem here. A lot of insects can be very host-specific, and will only survive while they have their host-plant around. As soon as the plant dies-off, they should go too.

Take care,

Jason

[earthdragon64]

It just strikes me as a bad idea that we are going to try and control an introduced, invasive alien species, with another introduced, alien species.

Hopefully it won't all end in tears.

[Jason Green]

Originally Posted by earthdragon64

It just strikes me as a bad idea that we are going to try and control an introduced, invasive alien species, with another introduced, alien species.

Hopefully it won't all end in tears.

I see what you mean, but with the Harlequin we knew it had a fairly wide-ranging diet - with this one it only goes for the sap of likely the one plant. As soon as the plant dies, so should this Psyllid in that area. Psyllids are on the menu of several UK invertebrates, so I doubt it will get out of control either! Of course, we don't even know if they will happily breed in this climate.

[Stinky Bob]

Originally Posted by Jason Green

Hello all,

I was just about to post this myself! When running a quick Google search on the Psyllid I came across a near-identical BBC report from 2008 when the plan was submitted to the Government for approval... BBC NEWS | Science & Environment | Predators could be superweed fix - and a subsequent WAB thread from the same year... Japanese Knotweed versus Aphalara itadori

I don't forsee a non-native Vs. native, Harlequin-style problem here. A lot of insects can be very host-specific, and will only survive while they have their host-plant around. As soon as the plant dies-off, they should go too.

Take care,

Jason

I doubt it will ever be a case of eradicating this particular plant, just control. Because I very much doubt when people find this in their gardens they will make the effort and take it to a licensed landfill site, I bet they dont even realise that it is illegal to take it down to the local landfill and as it only requires 7gm of plant material to reproduce then I cannot ever see being totally eradicated.

[tom00_uk]

i provided some of the funding to this project a number of years ago via my previous employer.

the tests have been carried out by cabi bioscience a not for profit business that has carried out projects around the world.

the control measure is just that a control, it will weaken the plant but not eradicate it. To start with there will be a population boom of the moth but then they will reach equilibrium. Weakened individual plants might not survive winter and so reduce the density of clumps and allow other plants to recolonize and mean less herbicide is needed.

Its going to save sending as much of the plant to hazardous waste landfill sites which must be a good thing with the limited space and the cost involved.

[Chiltern Ben]

Hi, (Chiltern Ben’s Dad – my account isn’t working)

I deal with JK professionally and have been following the CABI work on Aphalara itadori for years. I’ve seen some of the research work going on behind the scenes and as far as can be guaranteed in any dynamic biological system, this beast always chooses death rather than attacking anything else. However, we all know that evolution often finds a way, so this is down to risk and on which side of the line you stand.

I agree that releasing non-native species is an unpalatable risk but as long as we let garden centres, pet shops / fish sellers etc. sell alien species which have had no research on their likely effects or worrying about the viral, bacterial or seed / spore contamination they bring in, I’d rather have the option of releasing a beast that has been researched literally to death over many years and generations (of the psyllid bug, not the researchers!) to help save large scale habitats. Although I admit I’m uneasy about it.

Britain has one of the lowest biosecurity thresholds in the western world, so it’s not surprising we have invaders taking advantage of modern transport and changing our ever changing countryside. The problem is the speed of the change brought about by introduced species, out pacing the speed of adaptation by native species, rather than the fact that change is happening. Our present biodiversity is just a snapshot resulting from species reacting to natural process and anthropomorphic pressures e.g. development, farming practices, water abstraction, disturbance, habitat fragmentation, climate change etc. It’s dynamic, ever changing, whether we like it or not and it's not really predictable.

I don’t think there is a single right answer; it’s down to risk v damage (to native wildlife including species, habitats and diversity, the landscape, the economy etc.), on a species by species basis. Often we don’t have a good idea of what the risks and damage are going to be – this makes decisions into just opinion. Why not look at the Invasive Non-native Species Framework Strategy for GB, pick your favourite invasive species and decide what you’d do based on impact, cost and risk – do nothing, mitigate, control or eradication. Would you sit back and watch what happens (bye bye water voles and wc crayfish), go to war using chemicals and manual removal (who pays?) or bring in species specific predators i.e. biocontrol? It’s not an easy choice and there are no 100% guarantees any particular strategy will work or might even make things worse e.g. signal crayfish removal.

Finally I’d like to quote Donald Rumsfeld (never said that before ) albeit he was not thinking about UK invasive species but maybe he was!! – “There are known knowns. There are things we know we know. We also know there are known unknowns. That is to say, we know there are some things we do not know. But there are also unknown unknowns, the ones we don’t know we don’t know .” That’s where we are with alien species and biocontrol.

Chris

[Gilbert Jessop]

CABI have produced a helpful video about bio-control including sections on Japanese knotweed and Himalayan balsam, which I found helpful and reassuring:
Dick Shaw's Japanese knotweed presentation on Vimeo