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Bt pesticide resistance
"Moosh:]" wrote:
On 29 Jul 2003 08:52:24 GMT, Brian Sandle posted: As we discussed with DDT, anything used for too long breeds resistant creatures. So? The point is that the use of BT in the plant and on the plant is hardly different. When the insects are not present, they can't be developing resistance. Where is there a place without insects? Welcome to the real world, where things are not black and white, where we don't have either 0 or trillions of insects but varying degrees inbetween, where not all insects are dumb enough to keep eating bt until they've got a fatal dose but different ones eat different amounts and so trigger varying amounts of selective pressure. When the pesticide is interrupted then resistance to it is no longer an advantage. And the pest destroys your crop, and you go bankrupt. Not necessarily, if the natural predators have not been wiped out by overuse of pesticides and the plants natural defenses have not been weakened by toxic and/or cultural damage to the soil ecology. Then DDT will work again, or Bt. But if it is there all the time resistance to it remains an advantage for pests. Sorry, "there all the time" means nothing if the pests are not there. It might as well be withdrawn if the pests are absent. No contact, no advantage for the resistant mutations. When home gardners use it, or non-GM soy farmers &c, it is only present as needed, then disappears. And why does it matter if it's there or not, if the pests aren't predating the crop? There are always a few about, from the mandatory refuges, or other crops near by. But how does this matter? The chances of a resistance mutation are so much lower. Check out what's already happened: Independent on Sunday (London) March 30, 2003 INSECTS THRIVE ON GM 'PEST-KILLING' CROPS BY GEOFFREY LEAN ENVIRONMENT EDITOR Genetically modified crops specially engineered to kill pests in fact nourish them, startling new research has revealed. Biotech companies have added genes from a naturally occurring poison, Bacillus thuringiensis (Bt), which is widely used as a pesticide by organic farmers. Drawbacks have already emerged, with pests becoming resistant to the toxin. Environmentalists say that resistance develops all the faster because the insects are constantly exposed to it in the plants, rather than being subject to occasional spraying. But the new research - by scientists at Imperial College London and the Universidad Simon Rodrigues in Caracas, Venezuela - adds an alarming new twist, suggesting that pests can actually use the poison as a food and that the crops, rather than automatically controlling them, can actually help them to thrive. They fed resistant larvae of the diamondback moth - an increasingly troublesome pest in the southern US and in the tropics - on normal cabbage leaves and ones that had been treated with a Bt toxin. The larvae eating the treated leaves grew much faster and bigger - with a 56 per cent higher growth rate. They found that the larvae "are able to digest and utilise" the toxin and may be using it as a "supplementary food", adding that the presence of the poison "could have modified the nutritional balance in plants" for them. And they conclude: "Bt transgenic crops could therefore have unanticipated nutritionally favourable effects, increasing the fitness of resistant populations." The original scientific study is published at Ecology Letters Volume 6 Issue 3 Page 167 - March 2003 Could Bt transgenic crops have nutritionally favourable effects on resistant insects? Ali H. Sayyed, Hugo Cerda and Denis J. Wright Which product? When resistance develops to one insecticide, another must be used. Or somebody wakes up, thinks outside the box, and gets out of the pesticide trap. -- delete N0SPAAM to reply by email |
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