Biotech Cotton: A Budding Field: Steve Davidson Sums Up the Performance of Genetically-Modified Cotton in Australia

Article excerpt

In 1996, the first commercial genetically-modified crop was released in Australia. The crop was Ingard[R] cotton, a transgenic variety containing a gene from the soil bacterium, Bacillus thuringiensis or Bt, a microbe long used as a biopesticide in horticulture. Seven years on, it seems that, apart from the cotton's creator, the environment is its main beneficiary.

Ingard was developed from traditional high-yielding CSIRO cotton varieties in a partnership involving CSIRO, Cotton Seed Distributors and Monsanto.

The intention was to lessen pesticide use on Australian cotton farms, which are plagued by the cotton bollworm and the native bollworm (Helicoverpa species).

Similar caterpillars bother cotton crops in the United States, but Australian infestations are relatively extreme. Here, cotton growers might apply pesticides 12-14 times a season, at great cost, compared with two to five times in the US. ^^^ The engineered bacterial gene, Cry1Ac, causes cotton plants to produce an insecticidal protein that damages the gut of caterpillar pests, thereby reducing the need for pesticide applications.

How has it performed?

In the first year of its release, 30 000 hectares--8% of Australia's cotton crop--was planted to Ingard. Today, some 50% of our cotton fields grow genetically-modified varieties: either Ingard, or the herbicide-tolerant variety, Roundup Ready[R].

The performance of Ingard cotton was reviewed last year by Dr Danny Llewellyn and Dr TJ Higgins of CSIRO Plant Industry, and Dr Gary Fitt of CSIRO Entomology, chief executive officer of the Australian Cotton CRC in Narrabri, New South Wales. They concluded that the environmental benefits of the genetically-modified cotton were beyond question.

Monitoring by the Cotton Research and Development Corporation has shown that Ingard cotton requires 40--60% less pesticide than conventional cotton crops.

The greatest reductions have been in the use of endosulfan, carbamate and synthetic pyrethroid insecticides.

Endosulfan is a concern as a residue risk in export beef and is toxic to fish, while carbamates and synthetic pyrethroids are disruptive to beneficial insects.

As a bonus, the reduction in pesticide use, and the associated increase in helpful insects, enables growers to apply a suite of pest control measures known collectively as 'integrated pest management'.

The cost savings relating to Ingard, however, are not quite so straightforward: they are counteracted by the licence fee charged by Monsanto, owner of the Bt gene.

While the savings in pesticide costs may reach $180 a hectare, the licence fee is $155 a hectare. So the economic outcome of using Ingard could range from a net gain of $50 a hectare, to a net loss, depending on infestation levels and crop management efficiency.

But these economic analyses fail to address such intangibles as environmental benefits and ecological sustainability.

They undersell the true value of Bt cotton, as its real positive outcomes are still seen as environmental. Growers cite 'protection of the environment' as their main reason for choosing the genetically-modified crop.

Pre-empting resistance

From the outset, there has been concern that bollworms could develop resistance to Bt cotton.

Helicoverpa armigera has developed some degree of resistance to just about every chemical used against it, and both H. armigera and H. punctigera--Australia's worst cotton pests--are 10 times more tolerant of the Cry1Ac protein in Ingard cotton than the main target species in the US, H. virescens.

For these reasons, scientists and the cotton, industry have developed a resistance-management strategy that centres on the compulsory planting of specified 'refugia', or areas of conventional cotton or other crops adjacent to Bt crops.

As moths from the refuge crop disperse and mate with moths in the genetically-modified crop, they dilute the resistance genes that may have been selected by the By toxin. …