Japanese Knotweed

Beekeeper · #1 (**permalink**) 23-07-2009, 06:49 PM

It has been announced today that our wonderful government are considering importing another foreign species, this time an insect to help eliminate the Japanese Knotweed which is getting out of hand in our country.

I personally think this is a stupid idea, what happens when it has destroyed all the Knotweed, of course it will adapt and feed on something else which will almost certainly cause other problems, maybe to a native species of insect.

What are your views on this?

BK

ron1863 · #2 (**permalink**) 23-07-2009, 07:17 PM

Wonder if they will do the same with the American Mink - import coyotes, wolves, bears, great horned owls.

Acutipuerilis · #3 (**permalink**) 23-07-2009, 08:26 PM

To be fair to them in this case, they've done some attempt at testing its preferences, and the likelihood of it switching host, and chose this as the least problematic option. It doesn't kill the knotweed in Japan, but just inhibits it enough that other plants have a chance to get even.

The beastie in question is a psyllid, and these are normally quite strict in host preference. Although there are some that feed on entire families of plants, or an even wider selection, most are restricted to one or two species. Very few are major pests, and there have been quite a few imports from foreign parts. For example, the Eucalyptus psyllid Ctenarytaina eucalypti is a major problem for cultivated eucalypts, but has not spread to anything else.

In general, importing foreign species is *bad*, I agree. This case seems to be an ideal option for the knotweed problem, though, which has so far resisted all attempts to subdue it. And to be honest, it's going to get here naturally at some point, anyway - there are enough Japanese travellers to the UK, and they're small bugs.

I think in this case it's worth the risk... but of course you can never predict all ends. It might start eating chaffinches instead.

KeenTeen17 · #4 (**permalink**) 23-07-2009, 08:34 PM

I don't think Japanese Knotweed is really the problem. I have only seen it in a few places. Himalayan Balsam is much worse. Its hard to find somewhere that isn't rampant with it.

ron1863 · #5 (**permalink**) 23-07-2009, 09:10 PM

Quote:

Originally Posted by KeenTeen17

I don't think Japanese Knotweed is really the problem. I have only seen it in a few places. Himalayan Balsam is much worse. Its hard to find somewhere that isn't rampant with it.

We had an entire river bank at the bottom of our garden covered in Japanese Knotweed and were told we would never get rid of it. An old boy along the road told us to chop it down to ground level and remove any red leaves that popped up. We did that for a few years and are now weed free.

Acutipuerilis · #6 (**permalink**) 23-07-2009, 09:29 PM

We've got knotweed all along the canals up here, and it's rampant. There's too much of it for the chopping and plucking leaves lark to work, I'm afraid, although I'm glad to hear it's possible in a contained area!

Doing that for miles just wouldn't happen around here - perhaps mostly because the huge majority of the local population would never agree to some weeding duty, and most of the rest of us have to work.

ron1863 · #7 (**permalink**) 23-07-2009, 09:34 PM

I wouldn't even attempt it on a large stretch. Our back garden runs down a banking to the river, as does our six neighbours but the cutting does work. We only plucked for a short period as I levelled the banking and then used a flymow. Our bank is entirely weed free. Wish I could say the same about the neighbours

Beekeeper · #8 (**permalink**) 25-07-2009, 06:17 PM

Thanks for the replies folks, especially Acutipuerilis for the imformative post and also ron1863 for his interesting method of control.

Of course we should not be in this situation if there were strict controls on imports like those in Australia , and thanks to those controls, Australia is one of the few countries that have not got the Varroa mite which damages young Honey Bee larve, they are now boosting their economy to some degree by exporting bees and honey products to other countries.

Advantages all round, it seems.

BK

Adam Cheeseman · #9 (**permalink**) 25-07-2009, 06:27 PM

I think it has only ben given such consideration because of the expensive problems it causes the construction industry when the plant is present on a development site. The earth has to be cleared to a depth of at least 5m and is treated as contaminated soil and therefore can only be disposed of at certain waste disposal sites.

Cheers,

Adam