B. thurigiensis is mainly used to counter caterpillar infestations in brassicas. Most production will thus be entirely untreated. Both soap and pyrethroids, also used in organic farming, are non-carcinogenic, and break down quickly in the soil, while pyrethroids, at least, are rapidly degraded in the mammalian gut, not stored in fatty tissue, and are relatively non-toxic to mammals.
No, Professor Trewavas, I would not spray my dinner with fly-killer and live bacteria, but if I did, my chances of surviving unscathed would be very much higher with the organic mix than with the industrial farmers' cocktail.
Further, should we not be discussing not only the quantity, but also the potency of carcinogens? Have we not evolved methods of countering natural carcinogens in food plants? If so Professor Trewavas's 0.01 per cent of extra carcinogens added by non-organic farmers are much more important. GM foods may eliminate this extra contamination, so we are left with the claim that the "organic" plants will have a naturally higher level of natural carcinogens, produced as a response to attack from bacteria and fungi. One does wonder how humans survived all this lethal food in the past without the help of chemists and molecular biologists.
Sherborne, DorsetReuse content