Oct 11, 2005

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ISBCA Symposium in Davos. Interview with Jörg Romeis

Bt Technology: New impetus to Integrated Pest Management

Genetically modified maize and cotton plants containing new genes which enable them to produce specific active substances (Bt toxins) to control pests are now grown in a large number of countries. Can these Bt plants make a contribution to Integrated Pest Management? – This was the subject of one of the main sessions at this year’s International Symposium on Biological Control of Arthropods from 12 – 16 September in Davos. Unlike the previous 2002 symposium in Hawaii, when only preliminary estimates could be made, this time it was possible to present analyses of several years of field trials in the USA, Australia and China. - GMO Safety spoke to Dr. Jörg Romeis, who, together with his American colleague Anthony Shelton, prepared the programme for this session.

Dr. Jörg Romeis, Co-organiser of the Symposium on Biological Control of Arthropods in Davos, is engaged in projects to assess the effects of transgenic plants on non-target organisms.

GMO Safety: Can you briefly explain the objectives of Integrated Pest Management and Biological Pest Control?

Jörg Romeis: To put it simply, Integrated Pest Management (IPM) aims to use all available measures to reduce the use of pesticides in the management of pests. The aim is to create an environmentally friendly and sustainable pest management system. Biological Pest Control is one such measure, which sets out to control harmful organisms by encouraging and releasing beneficial organisms. When discussing the environmental impact of Bt technology we therefore examine its effects on beneficial fauna very closely. We then compare the results with the situation in conventional, non-Bt fields.

GMO Safety: Bt technology claims to control pests in a targeted way without harming beneficial organisms and to save on chemical plant protection. These are key components of the IPM concept. Is Bt technology compatible with the aims of Integrated Pest Management?

Jörg Romeis: Yes, in principle. But we have to consider the different crop types individually and differentiate between regions. Bt varieties of cotton, sweet corn and corn in Spain are replacing the broad-spectrum insecticides which are normally used to control lepidopteran pests. All the results so far indicate that reducing the use of insecticides by growing Bt crops has a clear positive effect on beneficial organisms. However, this is not the case in the USA: there the cultivation of Bt maize has led to virtually no reduction in insecticide applications. This is due to the fact that, for economic and technical reasons, very little insecticide was actually used to control the key pest (the European corn borer Ostrinia nubilalis).

GMO Safety: In which countries and for which crops is Bt technology being discussed in conjunction with IPM programmes?

Jörg Romeis: Australia is the first that springs to mind. There until recently, lepidopteran pests were controlled almost exclusively by means of insecticides. When Bt cotton was grown, insecticide applications fell by almost 60 percent. In the 2004/05 season, two-gene cotton, with two variants of the Bt toxin, became available as well. As a result insecticide applications fell by as much as 95 percent. In Australia, Bt technology is now regarded as a key component of any sustainable IPM programme. Gary Fitt, a scientist involved in this area, presented a paper at Davos. When Bt crops were grown, beneficial insects were 3 – 4 times more abundant than with conventional crops. He maintains that the use of Bt cotton has changed public thinking in Australia. Bt technology has given new impetus to the IPM idea.

GMO Safety: Are there any arguments against the integration of Bt technology in IPM programmes?

Jörg Romeis: The potential for target pests to develop resistance has been put forward as a significant argument. If this were the case, we would have to resort to insecticides again. However so far this type of resistance has not emerged in field populations even after several years of large-scale cultivation.

If we look at the cultivation of Bt cotton in the USA and in China, it is noticeable that the use of insecticides there has fallen sharply. Occasionally secondary pests do emerge, especially aphids and bugs. The appearance of new pests is often fielded as an argument against the use of Bt crops, when actually the reverse is true. Bt plants act specifically to target caterpillars. With broad-spectrum insecticides no longer being used to control lepidopteran pests, other pests that were once controlled by these insecticides are now gaining the upper hand.

GMO Safety: Can you suggest any improvements to make Bt technology compatible with IPM?

Jörg Romeis: The sustainable use of Bt plants needs refining. Take for example Bt plants with two insecticide genes with different modes of action. The new two-gene Bt cotton plants are an effective way of preventing the development of resistance in pests. A further improvement would be to control the production of the Bt toxins using special promoters. This would ensure that the toxins were produced only where they were needed. One such example is a new Bt maize which is resistant to the Western corn rootworm (Diabrotica). The larvae of this pest only eat the roots of the maize plants, so it would be perfectly adequate for the Bt toxin to be produced only in the root.

GMO Safety: What conclusions can you draw from the symposium?

Jörg Romeis: Bt technology is relatively new and we understandably regard it with a certain degree of caution, maybe even scepticism. We must further improve the risk analyses which are carried out before new Bt plants are brought onto the market to reduce uncertainties. Experience gained from several years of field studies on large areas of cultivation can help in this respect. The results of a range of long-term field studies in the USA and Australia have just been published. All the results so far clearly indicate that, in contrast to conventional insecticides, Bt plants do not harm beneficial fauna. In my opinion Bt plants are indeed compatible with biological pest control and the IPM concept. At present the only question being asked is: “What will happen if we use Bt plants?” We should also allow the question: “What happens if we don’t use Bt plants and continue as before?”