A biotechnology solution to insect pests in the case of cotton

The bacterium Bacillus thuringiensis (Bt) is a naturally occurring soil bacterium that produces insect-killing proteins. Bt sprays have been used as pesticides on both conventional and organic farms for many years.

By the early 1990s, the cotton bollworm had developed resistance to most chemical pesticides. Scientists working for the United States company Monsanto developed a cotton variety called Ingard®, which contains a gene derived from the Bt bacterium.

When the gene is inserted into cotton plants, they produce toxic proteins called Bt toxins that kill the bollworm caterpillars. The poison stays in the leaves and does no harm until the bollworm eats the leaf tissue. It is very specific — it only kills bollworm caterpillars and very closely related species. It does not affect humans or other animals.

In the 1990s, CSIRO Plant Industry scientists used licensed Monsanto genes to develop Bt cotton varieties that were suitable for Australian conditions. This variety was called Ingard® cotton.

In 1999, about 40 million hectares of GM Bt cotton were planted worldwide. In the same year, about one third of Australia 's cotton crop (100,000 hectares) was Bt cotton.

Some bollworm caterpillars may be resistant to Bt, which means that Bt cotton crops still need to be sprayed with insecticides to kill any surviving caterpillars. However, the introduction of Ingard® cotton greatly reduced the amount of insecticide spray used on cotton crops.

The CSIRO has since created a new form of Bt cotton, known as Bollgard®II, which also uses licensed Monsanto genes. Bollgard®II is Ingard® cotton with an additional different Bt insecticidal gene. Having two genes significantly reduces the possibility of the bollworm developing resistance to the Bt toxins.

Bollgard®II cotton has reduced pesticide use in Australia by up to 80 per cent compared to conventional varieties.

For more information about Bt cotton, go to: http://www.csiro.au/resources/bollgard.html

And on GM cotton in Australia: http://www.afaa.com.au/n_agbiotech_resources_landing.asp#cotton_oz

Companies including Monsanto, Syngenta, Dow AgroSciences, and Bayer CropScience have developed varieties of cotton with built-in resistance to the bollworm, and other scientists are researching the use of viruses and venoms to kill cotton pests.