6. Resistance Management Strategies in New Zealand
Currently, there are no specific restrictions on the use of Bt sprays by home gardeners or farmers – conventional and organic. The environmental impact assessments for the eradication programmes for the painted apple moth and the white spotted tussock moth considered that the spray programmes were unlikely to create sufficient selection pressure for the moths to develop resistance.
There is no clear indication as to what genetically modified Bt crops (if any) might be released in New Zealand. However, Bt genes have been incorporated experimentally into plants such as white clover, potatoes and brassicas and there are a number of well-known and established pests that affect those crops, for example grass grub, porina moth, diamondback moth and potato tuber moth.
Knowledge of pest biology is critical for developing effective strategies to delay resistance. The body of reports and evidence from overseas experience with Bt crops is clearly relevant, but some of the pest-crop combinations are unique to New Zealand and will require specific consideration based on their ecological interactions (e.g. Wearing and Hokkanen 1994).
There has been considerable work since 1996, funded by the Foundation for Research, Science & Technology, to develop resistance management strategies for specific crops in New Zealand, building on plans and case-studies in Wearing and Hokkanen (1994) and earlier work by Wigley. The potential impacts on Bt resistance of key factors including choice of Bt toxin (Wigley unpublished), alternate hosts (Cameron et al. 1997), adult and larval movement (Cameron et al. 2002a), and refuge position (Cameron et al. 2002b) are currently being investigated in model systems using brassicas and potatoes. Progress to date is summarised in (Madhusudhan et al. 2000).
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Ministry of Agriculture and Forestry
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NEW ZEALAND
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