Bt Crops & Superpest Moths & Nematodes Pose Major Threat to Organic Farming
MUTATION COULD MAKE ORGANIC PESTICIDE USELESS
6 August, The Independent (UK)

Scientists have found the Achilles' heel of the world's most popular organic
pesticide. The findings could fatally undermine its role as a safe form of
insect control in the developing world.

The pesticide is favoured by organic farmers not just because of its
effectiveness but also because it is composed of toxins produced naturally
by microbes in the soil. However, researchers have identified a gene that
makes insects resistant to the toxins, rendering the pesticide useless.
For decades, organic farmers have sprayed their crops with Bacillus
thuringiensis (Bt), a bacterium that produces toxins poisonous to insects
and pests but harmless to other animals and humans. In more recent years,
biotechnologists have inserted key genes from the Bt microbe directly into
genetically modified crops to give them an inbuilt resistance to pests.
However, it was feared that this strategy could backfire because the more
crops that are grown with Bt genes, the more likely it is that resistance
would develop. Now, scientists believe this fear is justified, after
discovering a genetic mutation of a moth that attacks cotton plants, one of
the crops that have been genetically modified with Bt genes.

The international team of researchers, led by Fred Gould, professor of
entomology at North Carolina State University, said moths carrying two
copies of the gene were highly resistant to Bt toxins. The researchers
estimate that 0.15 per cent of moths in the wild currently carry the
resistance gene. But it could take just 10 years for this percentage to
increase to a point where it would pose a serious problem to farmers.
A separate group of scientists from the University of California at San
Diego have found that Bt resistance is also present in microscopic
roundworms, such as nematodes, which also pose a serious threat to crops.
Raffi Aroian, professor of biology at the university, said: There are
insects in the wild now with gene variants that allow them to be resistant
to Bt toxins. As more crops with Bt genes are planted, it is only a matter
of time before populations of Bt-resistant insects grow numerous enough to
become economically troublesome to farmers hoping to control them.
Professor Aroian's team found that a single mutation in a gene that disables
an enzyme in the insect pest's gut is responsible for imparting resistance
to a range of Bt toxins.

"For people using Bt toxins to control insects, this is a particularly
threatening scenario," Professor Aroian said. It means that resistance to a
range of pesticides based on Bt toxins can come about "with one swoop", he
said. "Even if Bt toxins weren't used to fight insects, nematodes are an
enormous problem. At the last estimate, which was 13 years ago, they caused
$80bn (£56bn) worth of crop damage a year."