michael adams wrote:
"Mike Lyle" wrote in message
...

Broadening the discussion, I wonder if it's time to stop the
importation of plants altogether. Is the, perhaps minor, increased
risk of introducing pests and diseases worth it, balanced against
any, perhaps modest, benefit?

--
Mike.



As a matter of interest which particular types of plants and
pests did you have in mind ?

Surely most economically beneficial and or horticulturally
interesting plants will have already been imported by now.

I think that would be part of my point, if I'd reached the stage of
having a clear point. I said I was wondering: I wasn't preaching. The
plants we now import _are_ generally horticulturally interesting
rather than economically beneficial, and, by Heaven, we import an
awful lot of them. Almost anything we actually need, economically or
scientifically, can come in as seed or tissue cultures: the problem
is likely to be what comes in with growing plants. The quarantine
provisions for these are insecure.

In addition, presumably both plants and pests need suitable
climatic
conditions to survive unaided. So this limits concern to plants and
pests originating in temperate zones similar to our own.

And, of course and inevitably, those are the regions from which most
of our imports come. Call that a limit if you like, and I couldn't
argue; but it's a very wide limit.

Whereas if it was case of importing exotic plants and accompanying
pests from Borneo then the remedy would simply be to turn the
greenhouse heating off in winter.

Much plant material including fungi, migrate naturally along with
other forms of wild life, birds, insects, in any case without any
help or hindrance from the human race. Regulations or no
regulations.

Well, that's all obvious. But the fewer the imports, the fewer, and
the smaller in number, the accompanying species: that's reasonably
obvious, too. I'm not one to fly into mindless conniptions about
sudden oak death, mitten crabs, invasive freshwater crayfish, grey
squirrels, NZ flatworms, Dutch elm disease, scorpions on the Isle of
Sheppey, and all of those: but I've been thinking about it for
years -- as has Professor Brasier of Forest Research and Imperial
College. He reckons "We don't move large numbers of animals around
the world for disease reasons, and we shouldn't do it for plants
either."

Brasier, as I mentioned in another post, has just presented a paper
on the subject at a DEFRA-backed RHS conference. He may be wrong; but
that doesn't make the issue trivial, or liable to summary dismissal
by minor verbal debating points.

--
Mike.