Effect Measure

Why do I think that this will end badly? From the UK:

Japanese knotweed was first introduced as an ornamental plant in the 19th Century. But with no natural enemies in the UK it soon raged out of control, wiping out surrounding wildlife and even destroying buildings. The invasive species, that can grow up to 13ft tall and break through concrete, causes around £150 million worth of damage every year.

Gardeners tried starving it of water, soaking it in toxic weedkiller and simply just ripping it up, but nothing worked – until now.

A tiny insect called a psyllid, about the size of a grain of sand, was found to fell the knotweed within a few weeks and is now to be introduced to sites across the country. The plant-jumping lice lay eggs on the weed and the hatched larvae suck out the sap. (Louise Gray, The Telegraph [UK])

The citizens of the UK have been assured that the new bug has been thoroughly tested and won’t itself become a pest. And just to be sure, they are testing it at three “secret sites” where they will be “closely watched.” And if while watching they see a problem? Well, they don’t say what will happen if there’s a problem, since they will be letting this remedy out into the wild. The genie will be out of the bottle.

While this is being pitched as a huge boon to gardeners, the quotes in the article were from civil engineers, for whom the Japanese knotweed is an expensive problem when they wish to build on overgrown lots. Anyway, what could go wrong? These are tiny insects who only like to eat the Japanese knotweed. When they’ve eaten these all up, I’m sure they’d never develop an appetite for any other meal. Like those roses the English love so much.

According to The Telegraph the UK has never used biocontrol before. So they are playing catch up and with this brilliant idea, can truly be said to be entering the 19th century.


  1. #1 Charlie B.
    March 10, 2010

    “According to The Telegraph the UK has never used biocontrol before.”

    Telegraph is wrong – ladybirds are used for aphid control and nematodes are used against slugs. I weep for the state of British science reporting.

  2. #2 iayork
    March 10, 2010

    I’m not an expert, but I do know that this sort of control has been used in North America since the 1940s, for many (certainly dozens, perhaps hundreds of?) different imported weed pests, and I’ve never heard of any problems arising from it — even in the very early days, before testing was anywhere near as stringent as it is today.

    (The best-known example is probably the beetle that was released in the early 1990s to control purple loosestrife, but I’m vaguely aware of many more.)

    Are there some instances where this has gone as badly as you suggest?

    (I’m talking here about this sort of invertebrate control of imported weeds — I do know that similar attempts to control vertebrate pests with vertebrate controls have been much more problematic.)

  3. #3 Keith
    March 10, 2010

    Like Revere I too have the feeling this will turn sour. Charlie B worries about the state of British science reporting (and so do I) but I worry far more about British science and the common-sense/logic of our scientists who can seriously not worry about this – to the extent of running an “open-air trial”. Deeply worrying!

  4. #4 revere
    March 10, 2010

    iayork, Charlie B.: My comments are based mostly on two ideas. The first is that this kind of control may or may not work on its own because we have many examples of unintended and unforeseen consequences since we are dealing with systems whose dynamics we still understand very little. We do know that simple non-linear systems can have very surprising and counter-intuitive results. The second is, given a highly plausible kind of unpredictability, whether the value of this irreversible intervention is worth the unknown nature of the risks, and if so, to whom? If the value goes to the construction industry so they can build faster and more easily and the risks go to horticulture or other segments of society, is this a well thought out policy? I’m not an expert, either, but I can ask the question.

  5. #5 Dunc
    March 10, 2010

    Whilst there certainly have been a number of well-known issues with biocontrol measures in the past, I’m not entirely sure that “If at first you don’t succeed, give up” is a good motto for a scientist. I expect that the whole “indoor fire” thing had a number of fairly disastrous false starts too…

  6. #6 Kevin
    March 10, 2010

    “Skinner: Well, I was wrong; the lizards are a godsend.
    Lisa: But isn’t that a bit short-sighted? What happens when we’re overrun by lizards?
    Skinner: No problem. We simply release wave after wave of Chinese needle snakes. They’ll wipe out the lizards.
    Lisa: But aren’t the snakes even worse?
    Skinner: Yes, but we’re prepared for that. We’ve lined up a fabulous type of gorilla that thrives on snake meat.
    Lisa: But then we’re stuck with gorillas!
    Skinner: No, that’s the beautiful part. When wintertime rolls around, the gorillas simply freeze to death.”

  7. #7 C. Corax
    March 10, 2010

    This is an interesting subject. I’m girding my loins to do battle with Asian bittersweet, a species that usually wins such battles. Alas, it is closely related to our native bittersweet species. Anyway, I poked around in teh Google. The first two links are PDFs.

    This Australian paper says there’s never been a problem:


    This paper from Hawai’i says that there have been:


    As does this one:


    It seems that by far the greatest risk is to closely-related native plant species.

  8. #8 Karl Withakay
    March 10, 2010

    She swallowed the spider to catch the fly,
    but I don’t know why she swallowed the fly…
    I guess she’ll die.


  9. #9 tony
    March 10, 2010

    Biocontrol is a time honored concept. In fact, the US was a leader in such controls until chemical pesticides came along. Whether this one is completely safe I can’t say but did you read the alternative? Hosing down the weed with Roundup, repeatedly, is pretty bad news.

    “Plants grow vigorously along roadsides, waste areas, streams and ditch banks and create dense colonies that exclude native vegetation and greatly alter natural tree regeneration. Established populations are extremely persistent and do not respond to mowing/cutting. Large infestations can be eliminated with approved herbicides, but treatments are costly and time consuming. It poses a significant threat in riparian areas, where it disperses during flood events rapidly colonizing scoured shorelines, islands and adjacent forest land.” – Oregon Division of Noxious Weed Control
    If you’ve ever seen a wetland or stream bed taken over by an invasive species, you might think differently about this. All that can be asked is controlled experiments conducted in greenhouses mimic natural conditions as much as possible before general release.

  10. #10 geodoc
    March 11, 2010

    My reflex reaction to this news was negative, too. But on reflection: it’s a risk/benefit call, like any other. It sounds like people have anticipated some of the obvious risks (this isn’t a naive 19th century let’s-introduce-rabbits-into-Australia type intervention). I don’t know enough about ecology in general or japanese knotweed in particular to know whether it’s the right decision, but I’m not sure it’s wise to write off biocontrol entirely just because it comes with risks attached.

  11. #11 Sharon Astyk
    March 11, 2010

    It could work. It could end badly. I would suggest that a useful additional strategy would be to begin to develop a market for Japanese knotweed, which is also a tasty edible. Because realistically, like most invasives, Japanese Knotweed’s primary requirements are human disturbance – it succeeds so well because like us, it is prolific colonizer that works well with others. That is, it isn’t a forest invader, but one that likes loose, friable, moist soils with plenty of sun – ie, gardens and fields. One of the best ways to control Japanese knotweed is smothering – while it can come up through concrete, it can’t tolerate flexible tarps which have enough give to smother it. But, of course, if your dream is a perfect lawn, you probably won’t want to mulch your lawn.

    There have been highly successful uses of this kind of control, but I do think that fundamentally our invasive species problem is that we’re not down with the plants that can actually live well around humans. They produce a nasty, vacant monoculture of course, but that’s pretty much what human entry into the landscape has led to.


  12. #12 Uncle Glenny
    March 11, 2010

    Revere, not very distant from me, has obviously had problems with the same vines that I do: pull one up and the roots, shallow that they may be, easily travel 50 feet away.

    Now, I’m not saying that Revere is an effete naturist, but there are some squirrels who would like to know more about this.

  13. #13 darwinsdog
    March 11, 2010

    Russian olive and Tamarix occur on my property along the Rio de la Plata in northwestern New Mexico. I harvest both these species for firewood and heat my home exclusively with wood. Currently, the USDA, in conjunction with state agricultural departments & universities, are evaluating Tamarix control by means of introduction of the exotic chrysomelid beetle Diorhabda elongata. A site of introduction of these beetles is the mouth of La Plata, near my property. If these beetles defoliate or kill Tamarix on my property, thereby depriving me of a source of fuelwood, I intend to consult an attorney with the view of filing a lawsuit against those involved with this exotic beetle introduction.

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