On Thu, 07 Aug 2003 07:20:22 -0700, Walter Epp
posted:

"Moosh:]" wrote:
On 29 Jul 2003 08:52:24 GMT, Brian Sandle
posted:
As we discussed with DDT, anything used for too long breeds resistant
creatures.

So? The point is that the use of BT in the plant and on the plant is
hardly different. When the insects are not present, they can't be
developing resistance.

Where is there a place without insects?

The relevant insects are those that damage the crop. If they don't,
they won't be ingesting BT.

Welcome to the real world, where things are not black and white,
where we don't have either 0 or trillions of insects but varying
degrees inbetween, where not all insects are dumb enough to
keep eating bt until they've got a fatal dose but different ones
eat different amounts and so trigger varying amounts of
selective pressure.

And this happens with applied BT, only better coz the BT slowly
reduces due to washing off and so on. So if you want to be accurate,
applied BT can be worse than expressed BT wrt resistance development.

When the pesticide is interrupted then resistance to it is no
longer an advantage.

And the pest destroys your crop, and you go bankrupt.

Not necessarily, if the natural predators have not been wiped
out by overuse of pesticides and the plants natural defenses
have not been weakened by toxic and/or cultural damage to
the soil ecology.

BT is very specific, so your fear of pest predator damage is
unfounded. Why are you postulating that the natural defences of the
plant will be weakened? What are you trying to say about the soil
ecology?

Then DDT will work again, or Bt. But if it is there all
the time resistance to it remains an advantage for pests.

Sorry, "there all the time" means nothing if the pests are not there.
It might as well be withdrawn if the pests are absent.
No contact, no advantage for the resistant mutations.

When home gardners use it, or non-GM soy farmers &c, it is only present as
needed, then disappears.

And why does it matter if it's there or not, if the pests aren't
predating the crop?

There are always a few about, from the mandatory refuges, or other crops
near by.

But how does this matter? The chances of a resistance mutation are so
much lower.

Check out what's already happened:
Independent on Sunday (London) March 30, 2003
INSECTS THRIVE ON GM 'PEST-KILLING' CROPS
BY GEOFFREY LEAN ENVIRONMENT EDITOR

Genetically modified crops specially engineered to kill pests in fact
nourish them, startling new research has revealed.

Biotech companies have added genes from a naturally occurring poison,
Bacillus thuringiensis (Bt), which is widely used as a pesticide by
organic farmers.
Drawbacks have already emerged, with pests becoming resistant to the
toxin. Environmentalists say that resistance develops all the faster
because the insects are constantly exposed to it in the plants, rather
than being subject to occasional spraying.

Occasional spraying will result in many occasions where dose is
sublethal. Ideal circumstances for resistance development.

But the new research - by scientists at Imperial College London and the
Universidad Simon Rodrigues in Caracas, Venezuela - adds an alarming new
twist, suggesting that pests can actually use the poison as a food and
that the crops, rather than automatically controlling them, can actually
help them to thrive.

BT is a protein, and can be used as a food by non-sensitive insects,
but then no more than any other protein.
Nothing magic about it.

They fed resistant larvae of the diamondback moth - an increasingly
troublesome pest in the southern US and in the tropics - on normal
cabbage leaves and ones that had been treated with a Bt toxin. The larvae
eating the treated leaves grew much faster and bigger - with a 56 per
cent higher growth rate.

Can you quote any of this study? It costs to read it, I believe.

They found that the larvae "are able to digest and utilise" the toxin and
may be using it as a "supplementary food", adding that the presence of the
poison "could have modified the nutritional balance in plants" for them.

Along with all the other thousands of proteins the plant supplies
them?

And they conclude: "Bt transgenic crops could therefore have
unanticipated nutritionally favourable effects, increasing the fitness of
resistant populations."
The original scientific study is published at
Ecology Letters Volume 6 Issue 3 Page 167 - March 2003
Could Bt transgenic crops have nutritionally favourable effects on
resistant insects?
Ali H. Sayyed, Hugo Cerda and Denis J. Wright

Which product? When resistance develops to one insecticide, another
must be used.

Or somebody wakes up, thinks outside the box, and gets out
of the pesticide trap.

We can't survive without pesticides. Afterall, plants have never been
able to for many millions of years.