GENTECH archive


Bt refuge is no disaster

Dear Joe:

Thanks for forwarding your email message to me. Since they won't let free thinkers like myself onto Ban-GEF (only those who are opposed to GE), I don't see those messages, nor can I reply there.

I know that it is a bit old fashioned, but I prefer to read an article before commenting on it, and out here in Australia we don't get Science as fast as you clever North American residents. In fact, I only have a copy now because a colleague in New York faxed it on down.

When I read the article, I was struck by how the paper did not claim as you did that "the refuge set aside to prevent spread of Bt resistance are actually accelerating spread of Bt resistant mutants" And for good reason; the refuge can't hasten the spread. The refuge only weakens selection pressure, as EVERY person who has modeled this system has found. If the resistant insects really are resistant, they can spread anyway on the transgenic corn. In fact, the resistant males will probably spread faster in the absence of a refuge because they will search further for mates.

I am still a proud promoter of the refuge concept. Perhaps because I have modeled it in detail and conducted experiments that have tested how well it works, I publish about it in prestigious places (eg., Philosophical Transactions of the Royal Society of London, Series B, Biological Sciences 1998, 353: 1777-1786) and you haven't. In fact, I remain regrettably unaware of any of your contributions in the field of resistance management or even population genetics or ecology. Still, I am also looking for even more effective resistance management options, and indeed have argued elsewhere that we should pyramid multiple Bt proteins.

Finally, because I do look at research papers with a critical eye, I note that
the key point about the inheritance of resistance and its implications for resistance management is not so much that resistance is recessive but that heterozygotes die on the transgenic plants. Huang and co-authors in the paper you cite allude to this point in their conclusions ("at higher dosages, all individuals are expected to be susceptible"). Under footnote 7, I note that "Neonates of the Dipel ES-resistant O. nubilalis strain were able to cause more damage than susceptible insects when placed on certain greenhouse-grown Bt maize hybrids (F. Huang, R. A. Higgins, L. L. Buschman, unpublished data)." This naturally begs the question of whether the resistant strain can be reared to adults exclusively on Bt corn, or if they cannot tolerant the crop as so many Bt spray-selected resistant strains fail to do.

I have already written the authors of the scientific report on this point.

I look forward to your regular return to Gentech, where we can again discuss your ideas in the bright light of a server that allows some debate.