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Environmental impact of conventional and Bt insecticidal cotton expressing one and two Cry genes in Australia

Oliver G. G. Knox A E , Greg A. Constable B , Bruce Pyke C and V. V. S. R. Gupta D
+ Author Affiliations
- Author Affiliations

A CSIRO Entomology, Locked Bag 59, Narrabri, NSW 2390, Australia.

B CSIRO Plant Industry, Locked Bag 59, Narrabri, NSW 2390, Australia.

C Cotton Research and Development Corporation, 2 Lloyd Street, PO Box 282, Narrabri, NSW 2390, Australia.

D CSIRO Entomology, Gate 5, Waite Road, Urrbrae, SA 5064, Australia.

E Corresponding author. Email:

Australian Journal of Agricultural Research 57(5) 501-509
Submitted: 18 October 2005  Accepted: 30 January 2006   Published: 17 May 2006


Genetically modified Bt cotton, expressing the Cry1Ac protein for specific insecticidal activity against economically significant lepidopteran pests, has been available commercially in Australia since 1996. This technology has been improved and superseded by the addition of a second gene, allowing new varieties to express both the Cry1Ac the Cry2Ab proteins.

Bt cotton offers several advantages to the grower, mainly through reduced insecticide spray requirements. The environmental benefits of reduced insecticide usage are assessed in this paper using the environmental impact quotient (EIQ). The assessment included consideration of the impact of the expressed transgenic proteins Cry1Ac and Cry2Ab. EIQ values of the Cry1Ac and Cry2Ab proteins were calculated at 9.9 and 7.9, respectively. Bt protein expression, plant biomass, insecticide application records, constituent of active ingredient, and insecticide EIQ values were used to produce an environmental impact (EI) value for insecticide use (kg a.i./ha) for conventional non-GM and single- and 2-gene Bt cotton for the 1997–98 to 2003–04 seasons. Inclusion of the Cry proteins in the assessment increased the EI values for Bt cotton by only 2%. The average insecticide EI value, for 2002–03 and 2003–04 seasons, for conventional cotton was 135 kg a.i./ha, whereas for the 2-gene Bt variety it was only 28 kg a.i./ha. Results of the EI evaluation indicate that, due to changes in insecticidal choice and reduction in usage, there was a reduction of >64% in EI from growing Bt cotton compared with conventional non-GM cotton in Australia.

Additional keywords: integrated pest management, INGARD®, Bollgard® II, environment, transgenic, genetically modified, Cry1Ac, Cry 2Ab, impact quotient.


This work was carried out under funding provided by the Cotton Research and Development Corporation, but would not have been possible without the work and data collection services provided by the Cotton Consultants Australia Inc.


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