South American weevils released in UK waterways to tackle invasive weed

[Hudds Lad]

14 minutes ago, IanD said:

So it's not a solution then, if CART doesn't have the money... 😉

 

(what is it, anyway -- thousands of little men with nets?)

It’d be little chaps in weed clearing boats, but labour intensive, inaccurate and vast amounts of the stuff to dispose of once collected, hence not cheap.  and i don’t think it’s a C&RT problem if Government is doing it.

 

I would suggest that until all the weed is gone that releasing weevils isn’t a solution either, it’s an attempt at one.

[IanD]

19 minutes ago, Hudds Lad said:

It’d be little chaps in weed clearing boats, but labour intensive, inaccurate and vast amounts of the stuff to dispose of once collected, hence not cheap.  and i don’t think it’s a C&RT problem if Government is doing it.

 

I would suggest that until all the weed is gone that releasing weevils isn’t a solution either, it’s an attempt at one.

 

I don't get your last point; surely nothing is a solution until it's been tried and found to work?

 

Biological control for both insects and plants has been used successfully in many cases, and when it works it's often the cheapest and most effective solution by far -- it doesn't always eliminate the nuisance completely, but often brings it back under control.

 

It has gone horribly wrong occasionally (e.g. cane toads), but that doesn't mean it shouldn't be tried against pennywort.

 

Boeing's 737 MAX disaster is not a valid reason never to fly on a plane again just in case the same thing happens... 😉

Edited May 17, 2022 by IanD

[tree monkey]

1 minute ago, Hudds Lad said:

 

 

I would suggest that until all the weed is gone that releasing weevils isn’t a solution either, it’s an attempt at one.

The weevils will control, or at least may control,  the weed, it's unlikely it will ever be a complete solution, in an ideal world this would be followed up by peeps with nets to target the much reduced infestation, but as that cost a lot of cash it's highly unlikely to happen 

Just now, IanD said:

 

I don't get your last point; surely nothing is a solution until it's been tried and found to work?

 

Biological control for both insects and plants has been used successfully in many cases, and when it works it's often the cheapest and most effective solution by far.

 

It has gone horribly wrong occasionally (e.g. cane toads), but that doesn't mean it shouldn't be tried against pennywort.

 

Boeing's 737 MAX disaster is not a valid reason never to fly on a plane again just in case the same thing happens... 😉

As mentioned biological control is normally just control, it will rarely totally deal with the issue, follow up mechanical/chemical or peeps with nets is needed to achieve full eradication 

[IanD]

2 minutes ago, tree monkey said:

The weevils will control, or at least may control,  the weed, it's unlikely it will ever be a complete solution, in an ideal world this would be followed up by peeps with nets to target the much reduced infestation, but as that cost a lot of cash it's highly unlikely to happen 

As mentioned biological control is normally just control, it will rarely totally deal with the issue, follow up mechanical/chemical or peeps with nets is needed to achieve full eradication 

True -- but if it greatly reduces the number of peeps with nets needed, then isn't that a success?

 

We shouldn't reject a good solution because it's not perfect; if we wait for a perfect solution, we could never get one... 😉

[tree monkey]

4 minutes ago, IanD said:

True -- but if it greatly reduces the number of peeps with nets needed, then isn't that a success?

 

We shouldn't reject a good solution because it's not perfect; if we wait for a perfect solution, we could never get one... 😉

Oh absolutely, if eradication is the goal a diverse approach is needed,  use the blunt instrument to deal with the gross issue and then the need for a more involved follow up is reduced but not removed.

 

NZ manage possums with a drop of poison bait and then send out trapper to both trap and remaining and monitor numbers until no more are trapped, it's the same approach just a different target

 

On the other hand if control if all that is needed the gross approach is all that required 

Edited May 17, 2022 by tree monkey

[doratheexplorer]

1 hour ago, IanD said:

The trouble is that it's impossible to prove a negative, such as "the weevils won't cause a problem" -- insist that something "must be 100% safe" and the end result is that you can never try *any* new solution out... 😞

 

You have to balance the small (very small, the experts say...) chance of the weevils causing a problem in the future against the 100% guaranteed chance that pennywort is causing a problem now, to which we don't have a solution...

Or you could look it a different way:  Balance the known and understood problem against the risk of causing an ecological catastrophe.

 

Risk assessments are done by considering likelihood AND severity.  You're only looking at likelihood which makes your equation incomplete.

 

Also, there are no 'solutions' to invasive species, only mitigation strategies.  Introducing weevils is just one of a raft of such strategies, but it's one which could potentially cause a far bigger problem than the one it's trying to solve.  And history has shown that this type of intervention has gone wrong time and time again.

 

 

[ditchcrawler]

How did Zanda and Grass carp get into our waterway system?

[Slow and Steady]

38 minutes ago, Hudds Lad said:

It’d be little chaps in weed clearing boats, but labour intensive, inaccurate and vast amounts of the stuff to dispose of once collected, hence not cheap.  and i don’t think it’s a C&RT problem if Government is doing it.

 

I would suggest that until all the weed is gone that releasing weevils isn’t a solution either, it’s an attempt at one.

CRT and the EA have both been razzing it with chemicals since at least 2007. 

EA blog in 2015

https://environmentagency.blog.gov.uk/2015/03/19/a-few-thoughts-on-pennywort/

"It’s not just the Environment Agency that has been involved in trying to eradicate this problem. We have worked very closely with the Canal & River Trust who undertakes spraying on the sections of the Grand Union Canal."

[IanD]

9 minutes ago, doratheexplorer said:

Or you could look it a different way:  Balance the known and understood problem against the risk of causing an ecological catastrophe.

 

Risk assessments are done by considering likelihood AND severity.  You're only looking at likelihood which makes your equation incomplete.

 

Also, there are no 'solutions' to invasive species, only mitigation strategies.  Introducing weevils is just one of a raft of such strategies, but it's one which could potentially cause a far bigger problem than the one it's trying to solve.  And history has shown that this type of intervention has gone wrong time and time again.

 

 

 

History has shown that this type of intervention has been successful in many cases (and is in use every day all over the world for pest control), but these don't make big headlines like the few times it's gone badly wrong.

 

Yes of course a risk assessment is needed, and one assumes that the "experts" have done this, because that's their job. This takes in both expected positive and unexpected negative effects -- both probability and severity -- because that's what risk assessments do (I've been involved in them).

 

If the balance is strongly in favour of the weevils (high probability of good positive effect, small probability of serious negative effect), then it makes sense to try them out.

 

Every new "thing" which is introduced goes through (or should do!) a process like this, because you can't prove a negative i.e. that something new is guaranteed 100% safe with no side-effects.

Edited May 17, 2022 by IanD

[Slow and Steady]

1 minute ago, ditchcrawler said:

How did Zanda and Grass carp get into our waterway system?

And American crayfish. It's hard to keep your eye on 80 million people.

Lets not forget puma in the fens - I saw one once.

[Mike Todd]

39 minutes ago, tree monkey said:

The weevils will control, or at least may control,  the weed, it's unlikely it will ever be a complete solution, in an ideal world this would be followed up by peeps with nets to target the much reduced infestation, but as that cost a lot of cash it's highly unlikely to happen 

As mentioned biological control is normally just control, it will rarely totally deal with the issue, follow up mechanical/chemical or peeps with nets is needed to achieve full eradication 

From a purely system point of view, I would not expect it to work 'totally'. If it works to a high degree then the weevils start to starve and either die out or find new diets. The latter would mean that new weevils will be needed and the latter could be the start of unintended consequences. If the weevils die out before the weeds then there will be small amounts of weed left to re-colonise in the absence of a predator.

 

Whilst I am aware that this kind of control has worked well in in well-controlled contexts, I would have thought that out in the open canals it is pretty difficult constantly to monitor and adjust the weevil quantity.

 

But, hey, if we never tried something new ()having done due diligence) then we would never move forward and, frankly, almost any boater would be grateful for a 90% reduction in weed on some stretches! I guess it will be easier to get the weevils off the prop than the dreaded weed.

 

(I posted this before IanD's very similar post above arrived in my 'inbox')

Edited May 17, 2022 by Mike Todd

[IanD]

1 minute ago, Slow and Steady said:

And American crayfish. It's hard to keep your eye on 80 million people.

Lets not forget puma in the fens - I saw one once.

 

Were any of these deliberately introduces as pest/weed controls after a thorough risk assessment (like the weevil proposal), or just escapees (like rhododendrons or terrapins)?

Edited May 17, 2022 by IanD

[tree monkey]

2 minutes ago, ditchcrawler said:

How did Zanda and Grass carp get into our waterway system?

Zander was introduced by idiot who thought it was a cool idea, apparently 9th Duke of Bedford, thanks to wiki, but not as a biological control, just one of the long list of idiot decisions to add exotics to the wild, think grey squirrels 

 

Apparently BW were involved with grass carp as a weed control thing, so that could be considered biological control, don't forget carp themselves, apart from crucian are not native to the UK anyway

 

To be honest our waterways are so full of introduced species and various hybrids thanks to the fishing world I'm not sure we can actually call much of what we have as truly, properly native species anymore 

 

 

 

 

 

 

 

[Slow and Steady]

3 minutes ago, IanD said:

 

Were any of these deliberately introduces as pest/weed controls after a thorough risk assessment (like the weevil proposal), or just escapees (like rhododendrons or terrapins)?

Escapees, but whether the EA "monitor" weevils or not what's the difference? They can monitor crayfish too but they can't turn back time in either case... or do they seriously think if these weevils become an unforeseen problem they can deal with it?

I'm not against the idea, but scientists eh? They can only foresee what they can foresee - a point you've made several times yourself. Most likely they'll be over-cautious and it won't have much effect if I was guessing.

[Ray T]

I don't know it this statement refers to South American weevil - "Over sexed, over paid and over here?"

[tree monkey]

10 minutes ago, Mike Todd said:

From a purely system point of view, I would not expect it to work 'totally'. If it works to a high degree then the weevils start to starve and either die out or find new diets. The latter would mean that new weevils will be needed and the latter could be the start of unintended consequences. If the weevils die out before the weeds then there will be small amounts of weed left to re-colonise in the absence of a predator.

 

Whilst I am aware that this kind of control has worked well in in well-controlled contexts, I would have thought that out in the open canals it is pretty difficult constantly to monitor and adjust the weevil quantity.

 

But, hey, if we never tried something new ()having done due diligence) then we would never move forward and, frankly, almost any boater would be grateful for a 90% reduction in weed on some stretches! I guess it will be easier to get the weevils off the prop than the dreaded weed.

 

(I posted this before IanD's very similar post above arrived in my 'inbox')

Yup, control is what it's about, it's highly unlikely biological control would achieve eradication outside of a controlled environment,  some sort of biological control is used for azolla and that keeps coming back.

 

It still makes me twitchy though, unforseen outcomes are just that unforeseen, natural systems are incredibly complex and most management attempts are best guess, releasing none native species into an alien habit is sketchy 

[IanD]

16 minutes ago, tree monkey said:

Yup, control is what it's about, it's highly unlikely biological control would achieve eradication outside of a controlled environment,  some sort of biological control is used for azolla and that keeps coming back.

 

It still makes me twitchy though, unforseen outcomes are just that unforeseen, natural systems are incredibly complex and most management attempts are best guess, releasing none native species into an alien habit is sketchy 

Agreed, which is why you’d hope this has been carefully looked into, unlike accidental escapees.

 

Or CART could do nothing and wait for the deluge of complaints about the canals being choked with a pervasive weed... 😉

[tree monkey]

1 minute ago, IanD said:

Agreed, which is why you’d hope this has been carefully looked into, unlike accidental escapees.

 

Or CART could do nothing and wait for the deluge of complaints about the canals being choked with a pervasive weed... 😉

Let's hope it works, I really do hope it does, it still makes me twitch though 

[David Mack]

2 hours ago, MtB said:

 

 

To paraphrase richard benyon:

 

"I don't foresee any unforeseen problems".

 

 

Oh, the overconfidence of the technically incompetent politician. Not that there is any other sort. 

 

 

One of Donald Rumsfeld's "unknown unknowns".

[MtB]

16 minutes ago, David Mack said:

One of Donald Rumsfeld's "unknown unknowns".

 

 

Such a shame he got so pilloried for saying that. His observation and explanation of types of unknown makes perfect sense and was a good contribution to logical analysis.

 

 

 

 

[David Mack]

1 hour ago, MtB said:

 

Such a shame he got so pilloried for saying that. His observation and explanation of types of unknown makes perfect sense and was a good contribution to logical analysis.

I thought exactly that at the time. 

[PaulJ]

3 hours ago, IanD said:

 

(what is it, anyway -- thousands of little men with nets?)

EA are well up on this- we had loads in the River Great Ouse at the Bedford end . EA first collected it all up with the weed cutters and dumped it on the banks. Now months later they still do regular patrols in a dinghy with believe it or not a net, collecting the minuteist trace to prevent it coming back.

[Sea Dog]

As I understand it, extensive research whittled the choice down to just 2 candidates: a large variety and this rather smaller south American one. After that, the choice was straightforward for botanists since they have a long established course of action in such cases... 

 

Always choose the lesser of 2 weevils. 

[Alan de Enfield]

1 hour ago, Sea Dog said:

As I understand it, extensive research whittled the choice down to just 2 candidates: a large variety and this rather smaller south American one. After that, the choice was straightforward for botanists since they have a long established course of action in such cases... 

 

Always choose the lesser of 2 weevils. 

 

See the post from Moke (100s of posts ago) on page 1.

[john.k]

Water hyacinth and Nile cabbage......disappeared from the river s and dams here within six months of introduction of beetles.