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Integration of Bt Cotton in IPM Systems: an Australian Perspective

Fitt GP, Wilson L (2005). Second International Symposium on Biological Control of Arthropods.

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This paper is relevant to the Environmental categories in the following areas:

Crops:Cotton
Traits:Insect Resistance, and Insect Res. (BT)
Countries:Australia
Regions:Australia / NZ
ImpactAreas:Environmental

Abstract or Summary:

Insect pests may have a severe impact on cotton production in Australia. Key pests are
Helicoverpa spp which are well adapted to exploit cropping systems and often evolve resistance
to pesticides. Until recently adoption of IPM has been restricted by a lack of nondisruptive
tools.

IPM must be founded on a thorough understanding of the ecology of pest and beneficial
species, their interaction with the crop and surrounding non-crop environments. Insect resistant
transgenic cottons have proved successful in providing a foundation for more sustainable,
economically acceptable IPM with the integration of a range of other non-chemical
tactics.

In Australia, Bt cottons (tradename INGARD®) expressing the CryIAc endotoxin from
Bacillus thuringiensis subsp. kurstaki, were commercialised in 1996/97 and gradually increased
in area under an industry agreed deployment strategy which limited use to 30% of the cotton
area. Two gene (Cry IAc/Cry 2Ab) varieties (Bollgard II) have been commercialised from
2004/05 and have now completely replaced Ingard varieties. All Bt varieties are grown under
a comprehensive management strategy designed to minimise the risk of resistance evolving in
Helicoverpa armigera, the main target pest.

Commercial use of Ingard cotton varieties has reduced pesticide applications for
Helicoverpa spp by 60%, providing major environmental benefits. Even greater pesticide reductions
now occur with Bollgard II varieties. Pre-release environmental impact assessments
demonstrated no significant effect of these Bt cottons on natural enemies. Commercial experience
with Bt cotton crops has now shown a 3-4 fold increases in beneficial insect abundance
compared to conventional crops. Co-incidentally several selective insecticides (indoxacarb,
spinosad, and emamectin) became available for Helicoverpa control on conventional cotton,
which further assisted in conserving beneficials. While resistance is the greatest risk for Bt
cottons their sustained value in IPM systems also requires focus on the management of secondary
pests, which are suppressed in conventional cotton by Helicoverpa sprays. Enhanced
levels of beneficial species help to partially suppress secondary pests.

Maintaining an appropriate balance and retaining the benefits of Bt cottons requires
vigilant resistance management, sustained efforts to enhance beneficial species and non-disruptive,
short residual pesticides for key sucking pests. Overall the stability of these systems
will require mobilization of the whole farm environment and greater understanding of the
flows of impacts and services between intensive cropping systems and the surrounding landscape

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