"Torsten Brinch" wrote in message
...
On Fri, 08 Aug 2003 04:20:48 GMT, "Moosh:}"
wrote:

On Thu, 07 Aug 2003 07:20:22 -0700, Walter Epp
posted:
[Quoting Independent on Sunday (London) March 30, 2003:]
.. 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.

However, reminding ourselves of the perils of assumption-based
reasoning, let us hear what the experienced farmers over at
sci.agriculture has to say about that.

The idea of planting a refuge of non BT crop so the worms can feed on non BT
crops and inter breed with the millers raised on the BT crop was carefully
though out and seems to be working. There is some question if third world
farmers will abide by the refuge requirements but in most cases the small
field size and mixture of crops will provide alternate crops for the boll
worm to feed on and should produce enough millers that are not exposed to BT
to keep resistance down. Also they plan to change BT proteins periodically
to further reduce the likelihood of resistance. BollGard II is available
this year in Australia and I believe Bollguard I will not be available next
year. There are lots of BT proteins to choose from.

In http://ag.arizona.edu/pubs/general/r...nkbollworm.pdf 1 in 10
pink boll worms were found to be resistant to BT cotton in1997 the second
year BT cotton was grown. The resistant to the BT protein did not increase
in 98 or 99 with half the area in BT cotton. The lack of resistance to BT
developing was a surprise to the researchers who expected an increase in
resistance. So the refuge method seems to be sound.

More on the theory of refuges.
http://www.nature.com/nsu/990805/990805-5.html

Monsanto has traps world wide for boll worms and monitors the crops and
weeds around them by satellite imagery and on the ground inspection looking
for signs of resistance. It is one of their biggest nightmares and they are
doing every thing they can to spot it early and combat it should it arise.

We have been doing everything we can to extend the life of pesticides for
the last 20 years and hopefully we have learned something in that time.

Gordon