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#16
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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. |
#17
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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. |
#18
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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. |
#19
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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 :-) |
#20
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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. |
#21
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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. |
#22
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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 |
#23
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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. |
#24
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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? |
#25
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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. |
#26
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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? |
#27
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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. |
#28
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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. |
#29
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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? |
#30
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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.... |
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