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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 It might as well be withdrawn if the pests are absent.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 |
Bt pesticide resistance
On Thu, 07 Aug 2003 07:20:22 -0700, Walter Epp
posted: "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? The relevant insects are those that damage the crop. If they don't, they won't be ingesting BT. 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. And this happens with applied BT, only better coz the BT slowly reduces due to washing off and so on. So if you want to be accurate, applied BT can be worse than expressed BT wrt resistance development. 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. BT is very specific, so your fear of pest predator damage is unfounded. Why are you postulating that the natural defences of the plant will be weakened? What are you trying to say about 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. Occasional spraying will result in many occasions where dose is sublethal. Ideal circumstances for resistance development. 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. BT is a protein, and can be used as a food by non-sensitive insects, but then no more than any other protein. Nothing magic about it. 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. Can you quote any of this study? It costs to read it, I believe. 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. Along with all the other thousands of proteins the plant supplies 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. We can't survive without pesticides. Afterall, plants have never been able to for many millions of years. |
Bt pesticide resistance
Moosh:} writes
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. Can you quote any of this study? It costs to read it, I believe. 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. Along with all the other thousands of proteins the plant supplies The devil is in the detail, I suspect. I would be astonished if the amount of BT was enough to constitute a supplementary feed. However I can see an easy mechanism to produce this result, although whether this is true of this trial or not I cannot say. Plants attacked by pests will elevate their toxin levels as a response. If the untreated plants were under attack (or their neighbours were) then they would increase their toxin level. If the Bt plants perceived themselves in a pest-free environment then toxin levels would be low, if the untreated perceived themselves is a pest zone then they would elevate their toxin levels. The toxin levels in plants are known to have strong effects on growth rates of animals eating them. -- Oz This post is worth absolutely nothing and is probably fallacious. Note: soon (maybe already) only posts via despammed.com will be accepted. |
Bt pesticide resistance
On Fri, 8 Aug 2003 06:18:46 +0100, Oz
posted: Moosh:} writes 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. Can you quote any of this study? It costs to read it, I believe. 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. Along with all the other thousands of proteins the plant supplies The devil is in the detail, I suspect. I would be astonished if the amount of BT was enough to constitute a supplementary feed. However I can see an easy mechanism to produce this result, although whether this is true of this trial or not I cannot say. Plants attacked by pests will elevate their toxin levels as a response. If the untreated plants were under attack (or their neighbours were) then they would increase their toxin level. If the Bt plants perceived themselves in a pest-free environment then toxin levels would be low, if the untreated perceived themselves is a pest zone then they would elevate their toxin levels. The toxin levels in plants are known to have strong effects on growth rates of animals eating them. Interesting thoughts, thanks. I'm not rich enough to afford $19US for the dubious value of reading the full article. If someone else has it, then please post here. It amazed me that such a tiny amount of one protein could produce such growth differences. Your explanation of growth inhibition from a predated crop certainly fits. |
Bt pesticide resistance
On Fri, 08 Aug 2003 04:20:48 GMT, "Moosh:}"
wrote: On Thu, 07 Aug 2003 07:20:22 -0700, Walter Epp posted: [Quoting Independent on Sunday (London) March 30, 2003:] .. 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. Occasional spraying will result in many occasions where dose is sublethal. Ideal circumstances for resistance development. However, reminding ourselves of the perils of assumption-based reasoning, let us hear what the experienced farmers over at sci.agriculture has to say about that. .. |
Bt pesticide resistance
On Fri, 08 Aug 2003 05:48:09 GMT, "Moosh:}"
wrote: On Fri, 8 Aug 2003 06:18:46 +0100, Oz posted: Someone wrote: 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. .. Plants attacked by pests will elevate their toxin levels as a response. If the untreated plants were under attack (or their neighbours were) then they would increase their toxin level. .. It amazed me that such a tiny amount of one protein could produce such growth differences. Your explanation of growth inhibition from a predated crop certainly fits. It doesn't fit or explain anything at all, since the same cabbage leaf material was fed in all treatment groups in the experiment. The researchers grew a single cabbage crop, cut discs from its leaves, and fed the discs to different groups of larvae kept in petri dishes, with or without Bt toxin fortification. |
Bt pesticide resistance
Torsten Brinch writes
It doesn't fit or explain anything at all, since the same cabbage leaf material was fed in all treatment groups in the experiment. The researchers grew a single cabbage crop, cut discs from its leaves, and fed the discs to different groups of larvae kept in petri dishes, with or without Bt toxin fortification. What % DM was leaf and what BT in the two trials? What was the protein level in the DM of the two feeds? Were both groups fed ad-lib? I if the former was under 1% or so and the latter true then I would want to see independent verification. -- Oz This post is worth absolutely nothing and is probably fallacious. Note: soon (maybe already) only posts via despammed.com will be accepted. |
Bt pesticide resistance
Torsten Brinch writes
On Fri, 08 Aug 2003 04:20:48 GMT, "Moosh:}" wrote: On Thu, 07 Aug 2003 07:20:22 -0700, Walter Epp posted: [Quoting Independent on Sunday (London) March 30, 2003:] .. 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. Occasional spraying will result in many occasions where dose is sublethal. Ideal circumstances for resistance development. However, reminding ourselves of the perils of assumption-based reasoning, let us hear what the experienced farmers over at sci.agriculture has to say about that. There are two arguments: 1) Apply full dose and kill 99.999% except the 0.001% that have a resistance gene and next season you will have a 100% resistant population. If (as is common) you have a pest with a very high reproductive rate then you are stuffed in a year or two. This is what happened for dimfop resistant blackgrass. This might be typical of single gene resistance (not tolerance). This will happen whether or not the gene is less efficient than the 'natural' gene. 2) Apply a reduced rate, kill 99% of the pest, leave 1% of which 1:1000 have a resistance gene. Hope the resistance gives less efficient pest, outbred by 'natural' genes, leaving a final pest population still with about 0.001% resistance. So no change. Most field weeds are more tolerant of pesticides than their wild relatives, but often not by much. Pesticides acting on single genes are MUCH more likely to become completely useless due to single point mutation. Pesticides with multiple-point action are pretty unlikely to develop resistance. Obviously simultaneously using several pesticides with different action mimics multiple-point resistance. If a pesticide targets a key site, that is hard for the pest to alter because it is critical (perhaps used in many subsystems or is very basic), then tolerance rather than resistance seems to be the normal mode of action (eg hormone weedkillers, IPU). I haven't seen it stated, but I suspect the progeny are less competitive. Certainly resistant blackgrass seems to be highly susceptible to mildew, for example. -- Oz This post is worth absolutely nothing and is probably fallacious. Note: soon (maybe already) only posts via despammed.com will be accepted. |
Bt pesticide resistance
"Walter Epp" wrote in message ... "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. We have eliminated some insects. The new world screw worm fly has been killed back to the Panama canal and it use to range in to Kansas in the fall. It appears that with BT cotton, cultural practices, spraying scents that disrupt their breeding and releasing sterile males will do the job. http://www.soybeandigest.com/ar/soyb...pink_bollworm/ Once that is done that insect no longer needs any control measures unless that is a population in Mexico that we have to keep pushed back. And Mexico has been very cooperative on working with us on pest control. Unfortunately that won't work on common boll worms because they will eat about any thing there is. Gordon |
Bt pesticide resistance
"Torsten Brinch" wrote in message ... On Fri, 08 Aug 2003 04:20:48 GMT, "Moosh:}" wrote: On Thu, 07 Aug 2003 07:20:22 -0700, Walter Epp posted: [Quoting Independent on Sunday (London) March 30, 2003:] .. 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. Occasional spraying will result in many occasions where dose is sublethal. Ideal circumstances for resistance development. However, reminding ourselves of the perils of assumption-based reasoning, let us hear what the experienced farmers over at sci.agriculture has to say about that. The idea of planting a refuge of non BT crop so the worms can feed on non BT crops and inter breed with the millers raised on the BT crop was carefully though out and seems to be working. There is some question if third world farmers will abide by the refuge requirements but in most cases the small field size and mixture of crops will provide alternate crops for the boll worm to feed on and should produce enough millers that are not exposed to BT to keep resistance down. Also they plan to change BT proteins periodically to further reduce the likelihood of resistance. BollGard II is available this year in Australia and I believe Bollguard I will not be available next year. There are lots of BT proteins to choose from. In http://ag.arizona.edu/pubs/general/r...nkbollworm.pdf 1 in 10 pink boll worms were found to be resistant to BT cotton in1997 the second year BT cotton was grown. The resistant to the BT protein did not increase in 98 or 99 with half the area in BT cotton. The lack of resistance to BT developing was a surprise to the researchers who expected an increase in resistance. So the refuge method seems to be sound. More on the theory of refuges. http://www.nature.com/nsu/990805/990805-5.html Monsanto has traps world wide for boll worms and monitors the crops and weeds around them by satellite imagery and on the ground inspection looking for signs of resistance. It is one of their biggest nightmares and they are doing every thing they can to spot it early and combat it should it arise. We have been doing everything we can to extend the life of pesticides for the last 20 years and hopefully we have learned something in that time. Gordon |
Bt pesticide resistance
"Moosh:}" wrote:
On Thu, 07 Aug 2003 07:20:22 -0700, Walter Epp posted: "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? The relevant insects are those that damage the crop. If they don't, they won't be ingesting BT. but they can pass resistance genes to those who didn't ingest but can fly in and have a resistant feast. 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. And this happens with applied BT, only better coz the BT slowly reduces due to washing off and so on. So if you want to be accurate, applied BT can be worse than expressed BT wrt resistance development. Applied Bt is the most accurate way to minimize selective pressure. The crude approach of continual and high exposure makes for high selection pressure for resistance. 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. BT is very specific, so your fear of pest predator damage is unfounded. Why are you postulating that the natural defences of the plant will be weakened? What are you trying to say about the soil ecology? Mycorrhizal fungi can effectively connect their plant hosts with as much as 1,000 times more soil area than the roots themselves. A single gram of soil may contain several miles of fungal hyphae. As they pump water and mineral nutrients to the roots, the fungi form a protective armor against disease bacteria around the roots, and sometimes innoculate the soil with antibiotics that kill disease bacteria. Root zone fungi and bacteria exude glues (polysaccharides) that bind soil particles together, resulting in better retention and movement of air and water. Mycorrhizal fungi break down nitrogen into forms that can be used by plants. Mats of fungi in the soil store nutrients that otherwise would be likely to dissolve and leach away. Roundup/Glyphosate is toxic to many beneficial mycorrhizal fungi, inhibiting growth at levels as low as 1ppm, and increases susceptibility of crop plants to a number of diseases. The mycorrhizal hyphal network is easily disrupted by mechanical disturbance. Disking a field, for example, can greatly reduce the ability of the soil to make new plants mycorrhizal, even though no fungal material is actually removed by disking. 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. Occasional spraying will result in many occasions where dose is sublethal. Ideal circumstances for resistance development. If the spraying is only occasional the selection pressure is low. If the exposure is continual and high the selection pressure for resistance is high. -- delete N0SPAAM to reply by email |
Bt pesticide resistance
"Moosh:}" wrote:
On Thu, 07 Aug 2003 07:20:22 -0700, Walter Epp posted: "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? The relevant insects are those that damage the crop. If they don't, they won't be ingesting BT. but they can pass resistance genes to those who didn't ingest but can fly in and have a resistant feast. 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. And this happens with applied BT, only better coz the BT slowly reduces due to washing off and so on. So if you want to be accurate, applied BT can be worse than expressed BT wrt resistance development. Applied Bt is the most accurate way to minimize selective pressure. The crude approach of continual and high exposure makes for high selection pressure for resistance. 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. BT is very specific, so your fear of pest predator damage is unfounded. Why are you postulating that the natural defences of the plant will be weakened? What are you trying to say about the soil ecology? Mycorrhizal fungi can effectively connect their plant hosts with as much as 1,000 times more soil area than the roots themselves. A single gram of soil may contain several miles of fungal hyphae. As they pump water and mineral nutrients to the roots, the fungi form a protective armor against disease bacteria around the roots, and sometimes innoculate the soil with antibiotics that kill disease bacteria. Root zone fungi and bacteria exude glues (polysaccharides) that bind soil particles together, resulting in better retention and movement of air and water. Mycorrhizal fungi break down nitrogen into forms that can be used by plants. Mats of fungi in the soil store nutrients that otherwise would be likely to dissolve and leach away. Roundup/Glyphosate is toxic to many beneficial mycorrhizal fungi, inhibiting growth at levels as low as 1ppm, and increases susceptibility of crop plants to a number of diseases. The mycorrhizal hyphal network is easily disrupted by mechanical disturbance. Disking a field, for example, can greatly reduce the ability of the soil to make new plants mycorrhizal, even though no fungal material is actually removed by disking. 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. Occasional spraying will result in many occasions where dose is sublethal. Ideal circumstances for resistance development. If the spraying is only occasional the selection pressure is low. If the exposure is continual and high the selection pressure for resistance is high. -- delete N0SPAAM to reply by email |
Bt pesticide resistance
On Fri, 08 Aug 2003 17:30:23 +0200, Torsten Brinch
posted: On Fri, 08 Aug 2003 04:20:48 GMT, "Moosh:}" wrote: On Thu, 07 Aug 2003 07:20:22 -0700, Walter Epp posted: [Quoting Independent on Sunday (London) March 30, 2003:] .. 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. Occasional spraying will result in many occasions where dose is sublethal. Ideal circumstances for resistance development. However, reminding ourselves of the perils of assumption-based reasoning, let us hear what the experienced farmers over at sci.agriculture has to say about that. Of course, but it is a well known mechanism of resistance development, sub-lethal doses that leave the partially susceptible mutants still alive. Antibiotic treatments are a case in point. The importance of finishing the full course prescribed, and not stopping when you feel better. |
Bt pesticide resistance
On Fri, 08 Aug 2003 17:30:28 +0200, Torsten Brinch
posted: On Fri, 08 Aug 2003 05:48:09 GMT, "Moosh:}" wrote: On Fri, 8 Aug 2003 06:18:46 +0100, Oz posted: Someone wrote: 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. .. Plants attacked by pests will elevate their toxin levels as a response. If the untreated plants were under attack (or their neighbours were) then they would increase their toxin level. .. It amazed me that such a tiny amount of one protein could produce such growth differences. Your explanation of growth inhibition from a predated crop certainly fits. It doesn't fit or explain anything at all, since the same cabbage leaf material was fed in all treatment groups in the experiment. The researchers grew a single cabbage crop, cut discs from its leaves, and fed the discs to different groups of larvae kept in petri dishes, with or without Bt toxin fortification. You obviously have the advantage of reading the full paper. Care to share? So how do you explain the marked growth increase from this tiny amount of one protein? Has the experiment been replicated? If not, perhaps we should wait until the attempt has been made? |
Bt pesticide resistance
On Fri, 8 Aug 2003 17:15:49 +0100, Oz
posted: Torsten Brinch writes On Fri, 08 Aug 2003 04:20:48 GMT, "Moosh:}" wrote: On Thu, 07 Aug 2003 07:20:22 -0700, Walter Epp posted: [Quoting Independent on Sunday (London) March 30, 2003:] .. 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. Occasional spraying will result in many occasions where dose is sublethal. Ideal circumstances for resistance development. However, reminding ourselves of the perils of assumption-based reasoning, let us hear what the experienced farmers over at sci.agriculture has to say about that. There are two arguments: 1) Apply full dose and kill 99.999% except the 0.001% that have a resistance gene and next season you will have a 100% resistant population. If (as is common) you have a pest with a very high reproductive rate then you are stuffed in a year or two. This is what happened for dimfop resistant blackgrass. This might be typical of single gene resistance (not tolerance). This will happen whether or not the gene is less efficient than the 'natural' gene. 2) Apply a reduced rate, kill 99% of the pest, leave 1% of which 1:1000 have a resistance gene. Hope the resistance gives less efficient pest, outbred by 'natural' genes, leaving a final pest population still with about 0.001% resistance. So no change. Most field weeds are more tolerant of pesticides than their wild relatives, but often not by much. Pesticides acting on single genes are MUCH more likely to become completely useless due to single point mutation. Pesticides with multiple-point action are pretty unlikely to develop resistance. Obviously simultaneously using several pesticides with different action mimics multiple-point resistance. If a pesticide targets a key site, that is hard for the pest to alter because it is critical (perhaps used in many subsystems or is very basic), then tolerance rather than resistance seems to be the normal mode of action (eg hormone weedkillers, IPU). I haven't seen it stated, but I suspect the progeny are less competitive. Certainly resistant blackgrass seems to be highly susceptible to mildew, for example. Bottom line though is that BT expressed is no more likely fo cause resistance development problems than intemittent application of BT. |
Bt pesticide resistance
Mooshie peas writes
Bottom line though is that BT expressed is no more likely fo cause resistance development problems than intemittent application of BT. Hard to answer. The persistent and uniform use of any pesticide tends to lead to some level of resistance. The speed resistance arrives is rather variable and varies from locally almost immediate (eg dimfop) to hugely delayed (eg hormone weedkillers). Others allow decades of use before resistance is a problem (eg OP's). I suspect it depends on how easily the organism can bypass the pathways blocked by the pesticide. In the case of dimfop, a single change on a single gene seems to be enough. For OP's tolerance seems to develop by multiple gene changes, each of which confers a small tolerance, so resistance development is slow. In the case of hormones the auxin systems are so fundamental and old that it takes many rather large changes for true resistance to develop and we only see a partial tolerance. I would suggest from the evidence we have (ie no complete control failures) that Bt resistance is most likely to follow the second or third routes. Alternative GM insecticide molecules would, however, be advantageous, IMHO. -- Oz This post is worth absolutely nothing and is probably fallacious. Note: soon (maybe already) only posts via despammed.com will be accepted. |
Bt pesticide resistance
Mooshie peas writes
Of course, but it is a well known mechanism of resistance development, sub-lethal doses that leave the partially susceptible mutants still alive. Antibiotic treatments are a case in point. The importance of finishing the full course prescribed, and not stopping when you feel better. 1) A reminder that bacteria are much simpler than insects, and with a higher breeding rate. 2) No farmer applies pesticides in the above mentioned manner anyway. It varies from typically one to three applications per season. -- Oz This post is worth absolutely nothing and is probably fallacious. Note: soon (maybe already) only posts via despammed.com will be accepted. |
Bt pesticide resistance
On Tue, 12 Aug 2003 07:37:17 -0700, Walter Epp
posted: "Moosh:}" wrote: On Thu, 07 Aug 2003 07:20:22 -0700, Walter Epp posted: "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? The relevant insects are those that damage the crop. If they don't, they won't be ingesting BT. but they can pass resistance genes to those who didn't ingest but can fly in and have a resistant feast. Only if they breed with the resistant ones and have resistant offspring, but this happens all the time. 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. And this happens with applied BT, only better coz the BT slowly reduces due to washing off and so on. So if you want to be accurate, applied BT can be worse than expressed BT wrt resistance development. Applied Bt is the most accurate way to minimize selective pressure. The crude approach of continual and high exposure makes for high selection pressure for resistance. No, you apply everytime you have pest damage. That application wanes. If no pest damage, then there is no contact wih the expressed BT. The bottom line is it makes no difference in the end. Just get used to the fact that pesticides will lose their effect sooner or later, and new ones must be developed. The old ones may be returned to at a later date, and different strategies can be used to minimise resistance formation. Resistance 0ccurs whenever a pest is partially killed by a pesticide. This can happen with applied or expresssed BT at more or less the same rate. 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. BT is very specific, so your fear of pest predator damage is unfounded. Why are you postulating that the natural defences of the plant will be weakened? What are you trying to say about the soil ecology? Mycorrhizal fungi can effectively connect their plant hosts with as much as 1,000 times more soil area than the roots themselves. A single gram of soil may contain several miles of fungal hyphae. As they pump water and mineral nutrients to the roots, the fungi form a protective armor against disease bacteria around the roots, and sometimes innoculate the soil with antibiotics that kill disease bacteria. Root zone fungi and bacteria exude glues (polysaccharides) that bind soil particles together, resulting in better retention and movement of air and water. Mycorrhizal fungi break down nitrogen into forms that can be used by plants. Mats of fungi in the soil store nutrients that otherwise would be likely to dissolve and leach away. Roughly speaking. Roundup/Glyphosate is toxic to many beneficial mycorrhizal fungi, inhibiting growth at levels as low as 1ppm, and increases susceptibility of crop plants to a number of diseases. In vitro, I believe. Glyphosate will not reach the majority of the roots of fungal hyphae in real soils. It is too strongly bound to surface soil particles. Now the wetting agents may be a different matter. Dish liquid/hair shampoo is what caused the problems with amphibia. The mycorrhizal hyphal network is easily disrupted by mechanical disturbance. Disking a field, for example, can greatly reduce the ability of the soil to make new plants mycorrhizal, even though no fungal material is actually removed by disking. Exactly why "no till" using Roundup is so much better in so many places.. 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. Occasional spraying will result in many occasions where dose is sublethal. Ideal circumstances for resistance development. If the spraying is only occasional the selection pressure is low. Rubbish. If you kill half the pests occasionally, allowing the resistance gene to multiply and strentgen, you are going to get much more resistance problem. Keep up the 'cide constantly, and you kill many more pests. If the exposure is continual and high the selection pressure for resistance is high. The exposure is only continual when the pest are doing damage, so you would be applying continually anyway. There is very little difference. |
Bt pesticide resistance
On Wed, 13 Aug 2003 11:09:54 GMT, Mooshie peas
wrote: On Fri, 08 Aug 2003 17:30:28 +0200, Torsten Brinch posted: On Fri, 08 Aug 2003 05:48:09 GMT, "Moosh:}" wrote: On Fri, 8 Aug 2003 06:18:46 +0100, Oz posted: Someone wrote: 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. .. Plants attacked by pests will elevate their toxin levels as a response. If the untreated plants were under attack (or their neighbours were) then they would increase their toxin level. .. It amazed me that such a tiny amount of one protein could produce such growth differences. Your explanation of growth inhibition from a predated crop certainly fits. It doesn't fit or explain anything at all, since the same cabbage leaf material was fed in all treatment groups in the experiment. The researchers grew a single cabbage crop, cut discs from its leaves, and fed the discs to different groups of larvae kept in petri dishes, with or without Bt toxin fortification. You obviously have the advantage of reading the full paper. Care to share? So how do you explain the marked growth increase from this tiny amount of one protein? You mean the 56% increase? It is beyond me where the authors get that particular figure from. On the face of it the data shows a growth rate increase of only about 30 %, and I would be wary to accept even that. The main observation in the experiment IMO is that feeding BT fortified substrate (10ppm) to larvae, re-selected to yield high Bt resistance (LC50~200 ppm), increased their mean pupae weight significantly - about 20% - relative to feeding them non-BT fortified substrate -- while leaving their time to pupation unchanged or perhaps a bit shorter. Has the experiment been replicated? I don't know, Jack. You can ask the authors if they are working on that or something similar, email: h dot cerda at ic dot ac dot uk If not, perhaps we should wait until the attempt has been made? Funny you did not get that thought while you and Oz were happily explaining the findings. Boy, you couldn't even wait until you'd read the article :-) |
Bt pesticide resistance
On Wed, 13 Aug 2003 11:07:51 GMT, Mooshie peas
wrote: On Fri, 08 Aug 2003 17:30:23 +0200, Torsten Brinch posted: On Fri, 08 Aug 2003 04:20:48 GMT, "Moosh:}" wrote: On Thu, 07 Aug 2003 07:20:22 -0700, Walter Epp posted: [Quoting Independent on Sunday (London) March 30, 2003:] .. 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. Occasional spraying will result in many occasions where dose is sublethal. Ideal circumstances for resistance development. However, reminding ourselves of the perils of assumption-based reasoning, let us hear what the experienced farmers over at sci.agriculture has to say about that. Of course, but it is a well known mechanism of resistance development, sub-lethal doses that leave the partially susceptible mutants still alive. Antibiotic treatments are a case in point. The importance of finishing the full course prescribed, and not stopping when you feel better. Also, we should not forget to ask the agricultural scientist over at sci.agriculture whether resistance building is typically found where spraying has been done occasionally -- or whether resistance is more typically found where spraying has been done extensively, frequently or constantly. |
Bt pesticide resistance
Torsten Brinch writes
Also, we should not forget to ask the agricultural scientist over at sci.agriculture whether resistance building is typically found where spraying has been done occasionally -- or whether resistance is more typically found where spraying has been done extensively, frequently or constantly. Pests are typically too mobile for small plots not to be genetically similar to the wider environment. The spread of dimfop resistant blackgrass from a few sites to most of the blackgrass areas in the UK took (from memory) about five years. The precise pattern of resistance found in a field, though, seems to be related to the most recent applications, which is not unexpected. -- Oz This post is worth absolutely nothing and is probably fallacious. Note: soon (maybe already) only posts via despammed.com will be accepted. |
Bt pesticide resistance
On Wed, 13 Aug 2003 13:58:38 +0100, Oz
posted: Mooshie peas writes Bottom line though is that BT expressed is no more likely fo cause resistance development problems than intemittent application of BT. Hard to answer. The persistent and uniform use of any pesticide tends to lead to some level of resistance. The speed resistance arrives is rather variable and varies from locally almost immediate (eg dimfop) to hugely delayed (eg hormone weedkillers). Others allow decades of use before resistance is a problem (eg OP's). I suspect it depends on how easily the organism can bypass the pathways blocked by the pesticide. In the case of dimfop, a single change on a single gene seems to be enough. For OP's tolerance seems to develop by multiple gene changes, each of which confers a small tolerance, so resistance development is slow. In the case of hormones the auxin systems are so fundamental and old that it takes many rather large changes for true resistance to develop and we only see a partial tolerance. I would suggest from the evidence we have (ie no complete control failures) that Bt resistance is most likely to follow the second or third routes. Alternative GM insecticide molecules would, however, be advantageous, IMHO. -- Oz This post is worth absolutely nothing and is probably fallacious. You're too modest. Thanks :) |
Bt pesticide resistance
On Wed, 13 Aug 2003 14:00:59 +0100, Oz
posted: Mooshie peas writes Of course, but it is a well known mechanism of resistance development, sub-lethal doses that leave the partially susceptible mutants still alive. Antibiotic treatments are a case in point. The importance of finishing the full course prescribed, and not stopping when you feel better. 1) A reminder that bacteria are much simpler than insects, and with a higher breeding rate. Of course. But their biochemistry is quite similar, save for the speed of generation change. 2) No farmer applies pesticides in the above mentioned manner anyway. It varies from typically one to three applications per season. Of course, again, economics plays a strong role. Antibiotics are taken on the assumption that reinfection will not occur, whereas pests are constantly returning. |
Bt pesticide resistance
Mooshie peas wrote:
On Fri, 8 Aug 2003 17:15:49 +0100, Oz posted: Torsten Brinch writes On Fri, 08 Aug 2003 04:20:48 GMT, "Moosh:}" wrote: On Thu, 07 Aug 2003 07:20:22 -0700, Walter Epp posted: [Quoting Independent on Sunday (London) March 30, 2003:] .. 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. Occasional spraying will result in many occasions where dose is sublethal. Ideal circumstances for resistance development. Only if too little is applied. So with organic Bt a heavy dose is applied when needed. It degrades quite quickly so new generations of insects are not exposed to it. With GM Bt crops the dose much more gradually decreasses as the crop ripens. However, reminding ourselves of the perils of assumption-based reasoning, let us hear what the experienced farmers over at sci.agriculture has to say about that. There are two arguments: 1) Apply full dose and kill 99.999% except the 0.001% that have a resistance gene and next season you will have a 100% resistant population. If (as is common) you have a pest with a very high reproductive rate then you are stuffed in a year or two. This is what happened for dimfop resistant blackgrass. This might be typical of single gene resistance (not tolerance). This will happen whether or not the gene is less efficient than the 'natural' gene. 2) Apply a reduced rate, kill 99% of the pest, leave 1% of which 1:1000 have a resistance gene. Hope the resistance gives less efficient pest, outbred by 'natural' genes, leaving a final pest population still with about 0.001% resistance. So no change. Most field weeds are more tolerant of pesticides than their wild relatives, but often not by much. Pesticides acting on single genes are MUCH more likely to become completely useless due to single point mutation. Pesticides with multiple-point action are pretty unlikely to develop resistance. Obviously simultaneously using several pesticides with different action mimics multiple-point resistance. If a pesticide targets a key site, that is hard for the pest to alter because it is critical (perhaps used in many subsystems or is very basic), then tolerance rather than resistance seems to be the normal mode of action (eg hormone weedkillers, IPU). I haven't seen it stated, but I suspect the progeny are less competitive. Certainly resistant blackgrass seems to be highly susceptible to mildew, for example. Bottom line though is that BT expressed is no more likely fo cause resistance development problems than intemittent application of BT. No it is, because it always there selecting a bit. Why do you think the NZ Royal Commission recommended education about refuges before releasing GM crops? |
Bt pesticide resistance
Mooshie peas writes
On Wed, 13 Aug 2003 14:00:59 +0100, Oz posted: Mooshie peas writes Of course, but it is a well known mechanism of resistance development, sub-lethal doses that leave the partially susceptible mutants still alive. Antibiotic treatments are a case in point. The importance of finishing the full course prescribed, and not stopping when you feel better. 1) A reminder that bacteria are much simpler than insects, and with a higher breeding rate. Of course. But their biochemistry is quite similar, save for the speed of generation change. The plant genome is immense by comparison. 2) No farmer applies pesticides in the above mentioned manner anyway. It varies from typically one to three applications per season. Of course, again, economics plays a strong role. Antibiotics are taken on the assumption that reinfection will not occur, whereas pests are constantly returning. Indeed. The aim is to prevent significant damage, not to eradicate the pest for the season (except perhaps weeds). -- Oz This post is worth absolutely nothing and is probably fallacious. Note: soon (maybe already) only posts via despammed.com will be accepted. |
Bt pesticide resistance
On Wed, 13 Aug 2003 23:24:57 +0200, Torsten Brinch
posted: On Wed, 13 Aug 2003 11:09:54 GMT, Mooshie peas wrote: On Fri, 08 Aug 2003 17:30:28 +0200, Torsten Brinch posted: On Fri, 08 Aug 2003 05:48:09 GMT, "Moosh:}" wrote: On Fri, 8 Aug 2003 06:18:46 +0100, Oz posted: Someone wrote: 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. .. Plants attacked by pests will elevate their toxin levels as a response. If the untreated plants were under attack (or their neighbours were) then they would increase their toxin level. .. It amazed me that such a tiny amount of one protein could produce such growth differences. Your explanation of growth inhibition from a predated crop certainly fits. It doesn't fit or explain anything at all, since the same cabbage leaf material was fed in all treatment groups in the experiment. The researchers grew a single cabbage crop, cut discs from its leaves, and fed the discs to different groups of larvae kept in petri dishes, with or without Bt toxin fortification. You obviously have the advantage of reading the full paper. Care to share? So how do you explain the marked growth increase from this tiny amount of one protein? You mean the 56% increase? It is beyond me where the authors get that particular figure from. On the face of it the data shows a growth rate increase of only about 30 %, and I would be wary to accept even that. The main observation in the experiment IMO is that feeding BT fortified substrate (10ppm) to larvae, re-selected to yield high Bt resistance (LC50~200 ppm), increased their mean pupae weight significantly - about 20% - relative to feeding them non-BT fortified substrate -- while leaving their time to pupation unchanged or perhaps a bit shorter. Has the experiment been replicated? I don't know, Jack. You can ask the authors if they are working on that or something similar, email: h dot cerda at ic dot ac dot uk So how are you placing so much weight on this paper as to dismiss out of hand Oz's hypothesis? Without replication, this paper should be put on the "rubbish" spike "pending". BTW, have you heard of spam bots that can translate "dot" to "." and "at" to "@" and close up the spaces? :) If not, perhaps we should wait until the attempt has been made? Funny you did not get that thought while you and Oz were happily explaining the findings. You presume too much. The paper is out of my financial means (and I presume Oz is not willing to spend the required sum on the full paper) And we were merely "hypothesising" and wondering from the brief details we had seen. Even you can't explain the findings, having apparently read it. Boy, you couldn't even wait until you'd read the article :-) To discuss the findings that were mentioned on this group? Are you chronically constipated by any chance? |
Bt pesticide resistance
On Wed, 13 Aug 2003 23:24:58 +0200, Torsten Brinch
posted: On Wed, 13 Aug 2003 11:07:51 GMT, Mooshie peas wrote: On Fri, 08 Aug 2003 17:30:23 +0200, Torsten Brinch posted: On Fri, 08 Aug 2003 04:20:48 GMT, "Moosh:}" wrote: On Thu, 07 Aug 2003 07:20:22 -0700, Walter Epp posted: [Quoting Independent on Sunday (London) March 30, 2003:] .. 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. Occasional spraying will result in many occasions where dose is sublethal. Ideal circumstances for resistance development. However, reminding ourselves of the perils of assumption-based reasoning, let us hear what the experienced farmers over at sci.agriculture has to say about that. Of course, but it is a well known mechanism of resistance development, sub-lethal doses that leave the partially susceptible mutants still alive. Antibiotic treatments are a case in point. The importance of finishing the full course prescribed, and not stopping when you feel better. Also, we should not forget to ask the agricultural scientist over at sci.agriculture whether resistance building is typically found where spraying has been done occasionally -- or whether resistance is more typically found where spraying has been done extensively, frequently or constantly. Typically found wherever there is pesticide in contact with pests, I think you'll find. |
Bt pesticide resistance
On Tue, 19 Aug 2003 14:02:42 GMT, Mooshie peas
wrote: On Wed, 13 Aug 2003 23:24:57 +0200, Torsten Brinch posted: On Wed, 13 Aug 2003 11:09:54 GMT, Mooshie peas wrote: On Fri, 08 Aug 2003 17:30:28 +0200, Torsten Brinch The main observation in the experiment IMO is that feeding BT fortified substrate (10ppm) to larvae, re-selected to yield high Bt resistance (LC50~200 ppm), increased their mean pupae weight significantly - about 20% - relative to feeding them non-BT fortified substrate -- while leaving their time to pupation unchanged or perhaps a bit shorter. Has the experiment been replicated? I don't know, Jack. You can ask the authors if they are working on that or something similar, email: h dot cerda at ic dot ac dot uk So how are you placing so much weight on this paper as to dismiss out of hand Oz's hypothesis? snip I already explained why I think Oz's hypothesis as to what caused the observed difference is untenable. Look back the thread. |
Bt pesticide resistance
On 17 Aug 2003 12:53:23 GMT, Brian Sandle
posted: Mooshie peas wrote: On Fri, 8 Aug 2003 17:15:49 +0100, Oz posted: Torsten Brinch writes On Fri, 08 Aug 2003 04:20:48 GMT, "Moosh:}" wrote: On Thu, 07 Aug 2003 07:20:22 -0700, Walter Epp posted: [Quoting Independent on Sunday (London) March 30, 2003:] .. 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. Occasional spraying will result in many occasions where dose is sublethal. Ideal circumstances for resistance development. Only if too little is applied. And when too little is present. And this will be after EVERY application, as an application necessarily wanes. So with organic Bt a heavy dose is applied when needed. That would be constantly during a pest presence? You're dreaming. Only BT expression can do this. It degrades quite quickly so new generations of insects are not exposed to it. How long does it take to become a sublethal presence? How long does a sub-lethal level occur with intermittent application. How do you ensure that every pest that takes a bite from the crop gets a lethal dose. I put it to you that that's impossible without the even expression of the 'cide within the crop, continuously. With GM Bt crops the dose much more gradually decreasses as the crop ripens. But the pests are not feeding then? However, reminding ourselves of the perils of assumption-based reasoning, let us hear what the experienced farmers over at sci.agriculture has to say about that. There are two arguments: 1) Apply full dose and kill 99.999% except the 0.001% that have a resistance gene and next season you will have a 100% resistant population. If (as is common) you have a pest with a very high reproductive rate then you are stuffed in a year or two. This is what happened for dimfop resistant blackgrass. This might be typical of single gene resistance (not tolerance). This will happen whether or not the gene is less efficient than the 'natural' gene. 2) Apply a reduced rate, kill 99% of the pest, leave 1% of which 1:1000 have a resistance gene. Hope the resistance gives less efficient pest, outbred by 'natural' genes, leaving a final pest population still with about 0.001% resistance. So no change. Most field weeds are more tolerant of pesticides than their wild relatives, but often not by much. Pesticides acting on single genes are MUCH more likely to become completely useless due to single point mutation. Pesticides with multiple-point action are pretty unlikely to develop resistance. Obviously simultaneously using several pesticides with different action mimics multiple-point resistance. If a pesticide targets a key site, that is hard for the pest to alter because it is critical (perhaps used in many subsystems or is very basic), then tolerance rather than resistance seems to be the normal mode of action (eg hormone weedkillers, IPU). I haven't seen it stated, but I suspect the progeny are less competitive. Certainly resistant blackgrass seems to be highly susceptible to mildew, for example. Bottom line though is that BT expressed is no more likely fo cause resistance development problems than intemittent application of BT. No it is, because it always there selecting a bit. It can only select when pests are feeding, and when some pests are surviving it. Intermittent allows this after every application. Expression ensures a lethal dose at every bite (theoretically) Why do you think the NZ Royal Commission recommended education about refuges before releasing GM crops? The NZ RC has a bad taste in it's mouth after that lady professor lied to them with phony evidence. Aren't the refuges for pest predators? Why would you want refuges for the pests? |
Bt pesticide resistance
On Sun, 17 Aug 2003 17:54:49 +0100, Oz
posted: Mooshie peas writes On Wed, 13 Aug 2003 14:00:59 +0100, Oz posted: Mooshie peas writes Of course, but it is a well known mechanism of resistance development, sub-lethal doses that leave the partially susceptible mutants still alive. Antibiotic treatments are a case in point. The importance of finishing the full course prescribed, and not stopping when you feel better. 1) A reminder that bacteria are much simpler than insects, and with a higher breeding rate. Of course. But their biochemistry is quite similar, save for the speed of generation change. The plant genome is immense by comparison. Yep, but the biochemistry is surprisingly similar. 2) No farmer applies pesticides in the above mentioned manner anyway. It varies from typically one to three applications per season. Of course, again, economics plays a strong role. Antibiotics are taken on the assumption that reinfection will not occur, whereas pests are constantly returning. Indeed. The aim is to prevent significant damage, not to eradicate the pest for the season (except perhaps weeds). Sure, the aim is to get as much crop for as little expense as possible. With farsightedness, a smaller profit might be accepted for a likely increased profit over the next decade. The aim with pests might be to eradicate them forever :) but being pragmatic.... |
Bt pesticide resistance
Mooshie peas writes
On Sun, 17 Aug 2003 17:54:49 +0100, Oz posted: Mooshie peas writes On Wed, 13 Aug 2003 14:00:59 +0100, Oz posted: Mooshie peas writes Of course, but it is a well known mechanism of resistance development, sub-lethal doses that leave the partially susceptible mutants still alive. Antibiotic treatments are a case in point. The importance of finishing the full course prescribed, and not stopping when you feel better. 1) A reminder that bacteria are much simpler than insects, and with a higher breeding rate. Of course. But their biochemistry is quite similar, save for the speed of generation change. The plant genome is immense by comparison. Yep, but the biochemistry is surprisingly similar. No. A small subset is similar. 2) No farmer applies pesticides in the above mentioned manner anyway. It varies from typically one to three applications per season. Of course, again, economics plays a strong role. Antibiotics are taken on the assumption that reinfection will not occur, whereas pests are constantly returning. Indeed. The aim is to prevent significant damage, not to eradicate the pest for the season (except perhaps weeds). Sure, the aim is to get as much crop for as little expense as possible. With farsightedness, a smaller profit might be accepted for a likely increased profit over the next decade. The aim with pests might be to eradicate them forever :) but being pragmatic.... I know of no pests that have ever been eradicated, even in the heady days when DDT worked very well. -- Oz This post is worth absolutely nothing and is probably fallacious. Note: soon (maybe already) only posts via despammed.com will be accepted. |
Bt pesticide resistance
In sci.agriculture Mooshie peas wrote:
On 17 Aug 2003 12:53:23 GMT, Brian Sandle posted: Why do you think the NZ Royal Commission recommended education about refuges before releasing GM crops? The NZ RC has a bad taste in it's mouth after that lady professor lied to them with phony evidence. No she didn't. And the refuges are mandatory in the US. But the seed companies may not be insistant that they are applied since it means they only sell half the GM seed. Aren't the refuges for pest predators? Why would you want refuges for the pests? So there is a refuge of non-resistant pests to breed with resistant ones to reduce overall resistance. With organic Bt spray it is applied in years when the pests are a problem. In the intervening time when Bt is not being applied having Bt resistant genes is not an advantage, so the non-resistant ones increase and the next application of Bt when needed will cut them well back again. |
Bt pesticide resistance
"Oz" wrote in message ... Mooshie peas writes On Sun, 17 Aug 2003 17:54:49 +0100, Oz posted: Mooshie peas writes On Wed, 13 Aug 2003 14:00:59 +0100, Oz posted: Mooshie peas writes Of course, but it is a well known mechanism of resistance development, sub-lethal doses that leave the partially susceptible mutants still alive. Antibiotic treatments are a case in point. The importance of finishing the full course prescribed, and not stopping when you feel better. 1) A reminder that bacteria are much simpler than insects, and with a higher breeding rate. Of course. But their biochemistry is quite similar, save for the speed of generation change. The plant genome is immense by comparison. Yep, but the biochemistry is surprisingly similar. No. A small subset is similar. 2) No farmer applies pesticides in the above mentioned manner anyway. It varies from typically one to three applications per season. Of course, again, economics plays a strong role. Antibiotics are taken on the assumption that reinfection will not occur, whereas pests are constantly returning. Indeed. The aim is to prevent significant damage, not to eradicate the pest for the season (except perhaps weeds). Sure, the aim is to get as much crop for as little expense as possible. With farsightedness, a smaller profit might be accepted for a likely increased profit over the next decade. The aim with pests might be to eradicate them forever :) but being pragmatic.... I know of no pests that have ever been eradicated, even in the heady days when DDT worked very well. The new worm screw worm fly has been pushed back from forays into Kansas to the Panama canal using sterail male fly resases in large numbres. Females only breed once. The have been errdicated from north america. They lay the egg on a open wound and the maggog eats living flesh. Naval cords are the wrost place for and infection. Somtimes one infestation will kill a calf and two always will. Occasional some one will get in a fight and the screw worm fly will lay eggs on a bloody nose. If the don't seek medical help befeor the worms eat through to the brain they die very bad death. The program started right after WWII the last out break that reach Oklahoma was in 1972 and we have been pushing the as far away as we can get them into the narrow isthmus of Panama to reduce costs. Gordon |
Bt pesticide resistance
On Wed, 20 Aug 2003 06:58:29 +0100, Oz
posted: Mooshie peas writes On Sun, 17 Aug 2003 17:54:49 +0100, Oz posted: Mooshie peas writes On Wed, 13 Aug 2003 14:00:59 +0100, Oz posted: Mooshie peas writes Of course, but it is a well known mechanism of resistance development, sub-lethal doses that leave the partially susceptible mutants still alive. Antibiotic treatments are a case in point. The importance of finishing the full course prescribed, and not stopping when you feel better. 1) A reminder that bacteria are much simpler than insects, and with a higher breeding rate. Of course. But their biochemistry is quite similar, save for the speed of generation change. The plant genome is immense by comparison. Yep, but the biochemistry is surprisingly similar. No. A small subset is similar. Well most of the basic pathways IIRC. Sure bacteria don't do some of the sophistcated stuff that multicelled orgs do, so they don't need some of the enzymes used there. 2) No farmer applies pesticides in the above mentioned manner anyway. It varies from typically one to three applications per season. Of course, again, economics plays a strong role. Antibiotics are taken on the assumption that reinfection will not occur, whereas pests are constantly returning. Indeed. The aim is to prevent significant damage, not to eradicate the pest for the season (except perhaps weeds). Sure, the aim is to get as much crop for as little expense as possible. With farsightedness, a smaller profit might be accepted for a likely increased profit over the next decade. The aim with pests might be to eradicate them forever :) but being pragmatic.... I know of no pests that have ever been eradicated, even in the heady days when DDT worked very well. And the aim is to be perfectly good, yet I don't know one person who is. Doesn't detract from the aim. About the only thing that has been eliminated is a virus or two, theoretically. Is smallpox still kicking around? |
Bt pesticide resistance
On 20 Aug 2003 06:11:20 GMT, Brian Sandle
posted: In sci.agriculture Mooshie peas wrote: On 17 Aug 2003 12:53:23 GMT, Brian Sandle posted: Why do you think the NZ Royal Commission recommended education about refuges before releasing GM crops? The NZ RC has a bad taste in it's mouth after that lady professor lied to them with phony evidence. No she didn't. Yes she did. And the refuges are mandatory in the US. But the seed companies may not be insistant that they are applied since it means they only sell half the GM seed. Aren't the refuges for pest predators? Why would you want refuges for the pests? So there is a refuge of non-resistant pests to breed with resistant ones to reduce overall resistance. With organic Bt spray it is applied in years when the pests are a problem. In the intervening time when Bt is not being applied having Bt resistant genes is not an advantage, so the non-resistant ones increase and the next application of Bt when needed will cut them well back again. So what if intervening years have heavy pest predation too? You continue with the up and down levels of pesticide? The organic folk spray it all the time, they haven't anything else. Don't tell them that it is GM :) |
Bt pesticide resistance
Mooshie peas wrote:
On 20 Aug 2003 06:11:20 GMT, Brian Sandle posted: In sci.agriculture Mooshie peas wrote: On 17 Aug 2003 12:53:23 GMT, Brian Sandle posted: Why do you think the NZ Royal Commission recommended education about refuges before releasing GM crops? The NZ RC has a bad taste in it's mouth after that lady professor lied to them with phony evidence. No she didn't. Yes she did. She worked in the subject, and understands it. As you showed on sci.med.nutrition you even thought fish oil capsules are mainly peanut oil. And the refuges are mandatory in the US. But the seed companies may not be insistant that they are applied since it means they only sell half the GM seed. Aren't the refuges for pest predators? Why would you want refuges for the pests? So there is a refuge of non-resistant pests to breed with resistant ones to reduce overall resistance. With organic Bt spray it is applied in years when the pests are a problem. In the intervening time when Bt is not being applied having Bt resistant genes is not an advantage, so the non-resistant ones increase and the next application of Bt when needed will cut them well back again. So what if intervening years have heavy pest predation too? You continue with the up and down levels of pesticide? The organic folk spray it all the time, It is an important spray for them when significant pests are present, it is not used all the time. they haven't anything else. Organic farming is going big commercial so some very good practices such as companion planting and using other plants to discourage pests are not getting propoer attention. Don't tell them that it is GM :) That is a bit of a worry. Quite a few microbiological productive processes are using GM bacteria. Note what happened with the tryptophan produced by GM. I think such purifiaction as it was getting has always been sufficient with the non-GM approach. However in New Zealand the public were assured the moth spray does not have GM. I presume that is the Btk as well as the soy and corn medium it grows in when sprayed. |
Bt pesticide resistance
"Brian Sandle" wrote in message ... Mooshie peas wrote: On 20 Aug 2003 06:11:20 GMT, Brian Sandle posted: In sci.agriculture Mooshie peas wrote: On 17 Aug 2003 12:53:23 GMT, Brian Sandle posted: Why do you think the NZ Royal Commission recommended education about refuges before releasing GM crops? The NZ RC has a bad taste in it's mouth after that lady professor lied to them with phony evidence. No she didn't. Yes she did. She worked in the subject, and understands it. As you showed on sci.med.nutrition you even thought fish oil capsules are mainly peanut oil. And the refuges are mandatory in the US. But the seed companies may not be insistant that they are applied since it means they only sell half the GM seed. Aren't the refuges for pest predators? Why would you want refuges for the pests? So there is a refuge of non-resistant pests to breed with resistant ones to reduce overall resistance. With organic Bt spray it is applied in years when the pests are a problem. In the intervening time when Bt is not being applied having Bt resistant genes is not an advantage, so the non-resistant ones increase and the next application of Bt when needed will cut them well back again. So what if intervening years have heavy pest predation too? You continue with the up and down levels of pesticide? The organic folk spray it all the time, It is an important spray for them when significant pests are present, it is not used all the time. they haven't anything else. Organic farming is going big commercial so some very good practices such as companion planting and using other plants to discourage pests are not getting propoer attention. Don't tell them that it is GM :) That is a bit of a worry. Quite a few microbiological productive processes are using GM bacteria. Note what happened with the tryptophan produced by GM. I think such purifiaction as it was getting has always been sufficient with the non-GM approach. However in New Zealand the public were assured the moth spray does not have GM. I presume that is the Btk as well as the soy and corn medium it grows in when sprayed. She claimed association with Oregon State University. She actually had guest privileges to use one professors lab and a library card. I called and asked the department she was claiming association with. She had failed to make tenure in two departments at OSU. She referenced a paper that didn't exist. When it was later published it claimed 1 in 100 certainty with 90 trials and data that didn't agree with the findings was discarded with out being included an marked in the paper. The paper would get an undergrad a D or F were I come from. The lady takes a great deal of liberty with the truth. Gordon |
Bt pesticide resistance
In sci.med.nutrition Gordon Couger wrote:
"Brian Sandle" wrote in message ... She claimed association with Oregon State University. With your spelling, Gordon, maybe Open University, where she has been in charge of a dept rather than Oregen University. That is if it is who I think it is. How about some refs for this serious charge so we can patch up if necess. She actually had guest privileges to use one professors lab and a library card. I called and asked the department she was claiming association with. She had failed to make tenure in two departments at OSU. She referenced a paper that didn't exist. When it was later published it claimed 1 in 100 certainty with 90 trials So far so good, how many subjects per trial? and data that didn't agree with the findings was discarded with out being included an marked in the paper. That doesn't sound likely to be done. There could be other reasons for rejecting the data, maybe incompleteness. The paper would get an undergrad a D or F were I come from. The lady takes a great deal of liberty with the truth. Did she write the questionable paper or just quote it? If it has been found lacking following publishing has she been asked for comment? And why didn't the peer reviewers pick it up? |
Bt pesticide resistance
On 24 Aug 2003 03:23:31 GMT, Brian Sandle
posted: Mooshie peas wrote: On 20 Aug 2003 06:11:20 GMT, Brian Sandle posted: In sci.agriculture Mooshie peas wrote: On 17 Aug 2003 12:53:23 GMT, Brian Sandle posted: Why do you think the NZ Royal Commission recommended education about refuges before releasing GM crops? The NZ RC has a bad taste in it's mouth after that lady professor lied to them with phony evidence. No she didn't. Yes she did. She worked in the subject, and understands it. And lied about results she claimed to a Royal Commission. I wonder why someone who was so understanding of the subject needed to do this. As you showed on sci.med.nutrition you even thought fish oil capsules are mainly peanut oil. No, I suggsted that the balance of oils in an oil capsule would be the cheapst available, and peanut oil is a very common pharmaceutical vehicle. The poster was asking what the balance would be from the labelled ingredients. I still don't know that it is all fish oil, as if it makes any difference. What has this to do with lying about scientific evidence to a Royal Commission? And the refuges are mandatory in the US. But the seed companies may not be insistant that they are applied since it means they only sell half the GM seed. Aren't the refuges for pest predators? Why would you want refuges for the pests? So there is a refuge of non-resistant pests to breed with resistant ones to reduce overall resistance. With organic Bt spray it is applied in years when the pests are a problem. In the intervening time when Bt is not being applied having Bt resistant genes is not an advantage, so the non-resistant ones increase and the next application of Bt when needed will cut them well back again. So what if intervening years have heavy pest predation too? You continue with the up and down levels of pesticide? The organic folk spray it all the time, It is an important spray for them when significant pests are present, it is not used all the time. No, when the pests are doing damage. (IPM) And the BT expressed is not causing resistance if no pests are present. they haven't anything else. Organic farming is going big commercial so some very good practices such as companion planting Doesn't work, sorry. and using other plants to discourage pests are not getting propoer attention. What evidence have you got for this claim. Last I heard there was nothing in it. Wishful thinking. Don't tell them that it is GM :) That is a bit of a worry. Why? Its a very useful manufacturing technique. Quite a few microbiological productive processes are using GM bacteria. Note what happened with the tryptophan produced by GM. Nothing out of the ususal, except the factory took a short cut on quality control, and let a toxic byproduct through and poisoned some people with a well known poison. I think such purifiaction as it was getting has always been sufficient with the non-GM approach. Are you claiming there has never been any similar failures of quality control with bacterial production processes? However in New Zealand the public were assured the moth spray does not have GM. What does that mean? Does protein "A", produced by naturally occurring bacteria, and protein "A" produced by GM bacteria have any differences? I presume that is the Btk as well as the soy and corn medium it grows in when sprayed. What? Has NO connection with any GM process? |
Bt pesticide resistance
"Brian Sandle" wrote in message ... In sci.med.nutrition Gordon Couger wrote: "Brian Sandle" wrote in message ... She claimed association with Oregon State University. With your spelling, Gordon, maybe Open University, where she has been in charge of a dept rather than Oregen University. That is if it is who I think it is. How about some refs for this serious charge so we can patch up if necess. She actually had guest privileges to use one professors lab and a library card. I called and asked the department she was claiming association with. She had failed to make tenure in two departments at OSU. She referenced a paper that didn't exist. When it was later published it claimed 1 in 100 certainty with 90 trials So far so good, how many subjects per trial? and data that didn't agree with the findings was discarded with out being included an marked in the paper. That doesn't sound likely to be done. There could be other reasons for rejecting the data, maybe incompleteness. The paper would get an undergrad a D or F were I come from. The lady takes a great deal of liberty with the truth. Did she write the questionable paper or just quote it? If it has been found lacking following publishing has she been asked for comment? And why didn't the peer reviewers pick it up? It was an EPA paper no peer review. Gordon |
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