7. Where to From Here?
There is no doubt that maintaining the efficacy of Bt products is in New Zealand’s interests. The question is whether government regulation is required, and over which uses.
Home gardener use in New Zealand is probably not significant enough to be regulated as part of a resistance management strategy. No other garden insecticides are restricted in this way, and some other garden products are more widely used than Bt in commercial production. Restrictions on Bt may perversely create incentives for using more toxic alternatives and would also be extremely difficult to enforce. However, to properly assess whether it should be regulated, the amount of Bt used in home gardens in New Zealand needs to be estimated and compared against other uses.
Commercial farmers, particularly those using organic or integrated pest management methods use Bt sprays more extensively than home gardeners and could be subject to controls to manage resistance. These users have strong incentives to maintain the long-term effectiveness of Bt on a voluntary basis, though the only evidence of Bt resistance to date has arisen from over-use of Bt sprays. Proposals to limit the use of Bt sprays would need to consider the effect of disincentives to use Bt sprays compared to alternative sprays, and how the controls would be enforced.
If Bt crops were to be considered for field tests in New Zealand, appropriate choice of Bt transformations and the use of refuges could be required to manage pest resistance as part of the conditions of the field test. During the development and testing phase for any proposed Bt crop, effectiveness against specific pests should be assessed.
It is highly likely that approval to release Bt crops in New Zealand will only be granted if the applicant has satisfactorily addressed resistance management. This is because the continual presence of Bt toxins in genetically modified crops are thought to pose greater risk of accelerating resistance than the use of Bt sprays. While there is no ability at present to regulate the use of a genetically modified crop that has been approved for release, the government is considering the idea of conditional release. However, users of Bt crops will also have strong incentives to maintain the effectiveness of Bt over the long-term on a voluntary basis.
In summary, the government should consider the following questions/issues:
- The amount of Bt used by home gardeners and commercial farmers should be estimated and assessed for its potential to accelerate the development of resistance.
- Similarly, a decision to regulate Bt crops to delay resistance should be justified by assessing whether selection pressure applied to pests from the Bt crops is sufficiently different from other methods of controlling those pests, including the use of Bt sprays. The assessment should take account of the numbers of Bt plants being used, as well as their characteristics.
- If regulation is considered, the usual process of evaluating costs and benefits should be followed. In particular, monitoring and enforcement will be critical issues. For example, there may need to be some sort of third party audit system, and a way of collecting data about the amount and location of Bt crops being grown or Bt spray being used.
- The government should continue to consider the potential for resistance when using Bt sprays for biosecurity operations.
Potential applicants seeking to release genetically modified Bt crops in New Zealand should consider developing a resistance management strategy and should factor in the research required to generate sufficient information for the application. This research should include knowledge of the characteristics of the proposed crop and Bt construct to be released, together with an understanding of the biology and genetics of the targeted pests.
The most established methods of resistance management overseas involve using selected toxins and the refuge/high dose methods and these will potentially be of the most immediate use in New Zealand. The issues and requirements would depend case-by-case on the particular crop and its pests. When designing a resistance management system, the seven key elements identified by the USEPA should be considered:
- knowledge of pest biology and ecology;
- appropriate dose expression strategy;
- appropriate refuge;
- resistance monitoring and a remedial action plan should resistance occur;
- employment of integrated pest management;
- communication and education strategies on use of the product; and
- development of pesticides/constructs that have alternative modes of action.
In situations where agronomic knowledge is limited and likely to be case specific, offering registered products for sale and controlling their use is a challenge. Bt crops lend themselves well to being co-operatively managed, using both scientific knowledge (e.g. generalised as indicated in this paper, or more specific as available and needed) together with the specific local knowledge of the land manager (as alluded to in the case-studies). Plans reflecting the specific characteristics of the crop and the land can then be developed collaboratively and modified through time as understanding and knowledge increases. Such a programme will need to be scientifically developed in order to be effective. Its chances of success in implementing a resistance management programme will need to be assessed as part of the analysis. The criteria and the means by which success is measured will need to be established as part of the analysis.
Contact for Enquiries
Dr Sharon Adamson
Manager,
Innovation Policy
Ministry of Agriculture and Forestry
PO Box 2526
Wellington
NEW ZEALAND
Phone: +64 4 894 0618
Fax: +64 4 4 894 0741
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