GENTECH archive


Re: GM crops leak toxins, archive 2344

Herve wrote:

>I disagree with you : the conclusion you quote envisages
>promotion of selection. So there should be a pression of selection.

Selection on what? Stotsky has being doing work with Bt in soils for some years now, and so far as I can tell, has only run bioassays on horn worms. Horn worms live on and eat leaves, not soil. As Darwin and AR Wallace noted, before there can be selection, there must an effect on reproduction. What's a plausible organism?

>Yet (again!) if, as you quote, Bt can have efect on famrers, it must
>be that Bt has other effects than linked to the basicity of the gut of
>lepidopters (by the way what is the order of basicity needed to have Bt
>transformed into the insect-killer molecul(s) ?).

Hold on, the recent claims have been about the effects of Bt sprays and the spores they carry, NOT the insecticidal toxins, which have been checked and specifically excluded. "Basicity"? Ph about 10.

>Any example of organism submitted to a molecule toxic WILL develop
>resistance. The only question is when.

No the first question is to find an organism to test!

>Did one check lacewings fed with the eggs and aphids of corn borers (fed with Bt corn) ?

Even if someone did, critics would likely argue, "Well maybe Bt affects them in some other way." The key test is, does it affect field populations? That has been studied, and the field populations were not hurt by Bt corn (Pilcher et al. Environmental Entomology (1998, 26: 446-454).

My technician and I did feeding studies on lady beetles in aphids on Bt potatoes that control Colorado beetles (no adverse effects), but perhaps you'd prefer to believe the following citation. Whole field population studies have also been done for Bt potatoes by Reed of the authors below (again no effects, except that predators and parasitic wasps are much more common on Bt potatoes than most conventionally grown potatoes because the Bt potatoes are not sprayed for potato beetles).

Dogan, Berry, Reed and Rossignol. 1996. Biological parameters of
convergent lady beetle (Coleoptera: Coccinellidae) feeding on aphids
(Homoptera; Aphidae) on transgenic potato. J. Econ. Entomol. 89:1105-1108.