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2-Plants: Australian cotton belts pests into split views

-------------------------------- GENET-news -------------------------------

TITLE:  Cotton belts pests into split views
SOURCE: Canberra Times, Australia
DATE:   15 Jul 2004

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Cotton belts pests into split views

NEW RESEARCH suggests that farming of cotton plants genetically
engineered to kill caterpillars has halved pesticide use in Australian
cotton over the past six years.

Despite public concern about the risks, industry bodies plan to raise the
current 30 per cent cap on GE cotton as a proportion of the total crop
when a souped-up variety goes on the market next year. CSIRO scientists
predict this will see pesticide use on cotton drop by up to 80 per cent.

These figures are hotly disputed by Bob Phelps, director of the
Australian Gene Ethics Network, who says the 50 per cent reduction in
pesticide use is limited to GE crops and therefore equates to a modest
12-15 per cent reduction in pesticides across the Australian cotton
industry. He says the 80 per cent claim is hard to substantiate until the
new variety is in commercial use.

Early attempts to establish a large-scale cotton industry in Australia
were devastated by pests, particularly in the Ord River irrigation scheme
in Western Australia. But the industry has developed rapidly since the
crop was first introduced in the early 1960s.

Nearly half the world's total agricultural pesticides have been sprayed
on cotton since then. The use of these chemicals produced a much greater
cotton yield, but also plenty of problems: an annual average of $130
million spent on pesticides world-wide, accusations of polluting
waterways and causing health problems with spray drift, and the constant
threat the chemicals would lose their bite as insects became resistant to

Dr Gary Fitt, a world leader in the understanding and management of
insect pests in cotton crops and a director of CSIRO entomology based in
Narrabri, says the primary impetus for developing genetically modified
cotton varieties was to reduce the environmental impacts of the cotton

Research by CSIRO and United States chemical company Monsanto in the
early 1990s made it possible to arm cotton plants with a gene from the
soil microbe, Bacillus thuringiensis, which causes the plants to produce
a toxin which kills caterpillars when they eat the leaves.

"With conventional cotton and integrated pest-management strategies you
can make incremental improvements and gradually reduce pesticide use,"
says Fitt, "But Bt cotton was essentially a quantum leap forward."

After eight years' experience growing the variety, trademarked Ingard,
farmers say they have been able to reduce aerial sprays against
caterpillars by up to 56 per cent compared with conventional cotton.

"The use of Bt cotton has really played a role in allowing growers to
become more confident with managing their other pests in softer ways,"
says Fitt.

However, the modified cotton only remained effective against pests for
the first half of the season and there were concerns raised about the
possibility of insects developing resistance. "That's why a resistance-
management strategy was developed," says Fitt, "essentially to ensure we
never see resistance developing."

This included a 30 per cent cap on Bt cotton within the conventional
cotton crop (at a farm level) and refuge crops where pests are allowed to

If these insects, which haven't been exposed to Bt cotton, mate with
survivors from the Bt crops the risk of resistance developing in the
insect population is reduced. Finally, growers destroy the residue of the
crop by cultivation straight after harvest and eliminate any plants that
survive into the next year's crop.

Phelps says, "It's not really known whether [refuge crops] work at all,
whether the insects travel a hundred metres or half a kilometre from the
middle of the crop to the outside of the crop to mate with other insects."

He is concerned also that modified cotton may cross with native cotton
and weedy relatives to create super-fit weeds and says "the future of Bt
cotton as a crop that can be grown anywhere" is still an open question.

The latest step is to insert a second toxin gene creating a new double-Bt
cotton strain, Bollgard II. This gives cotton plants two independent
defences so that even if a mutation gives some caterpillars resistance to
one toxin, the back-up will still kill them.

While last year both varieties were commercially available, Ingard was
phased out on July 1 this year, leaving only Bollgard II on the market.

Trials suggest the new strain will provide increased protection from
pests for the whole growing season, leading the Australian Pesticide and
Veterinary Medicines Authority to lift the cap on Bt cotton crops. Fitt
argues that when refuge crop requirements are taken into account, farmers
will be able to grow up to 90 per cent Bt cotton, making possible an 80
per cent reduction in pesticide.


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