Stewardship of Resistance

Don Lee Author

09/23/2019 Added

10 Plays

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Preventing weed resistance to chemical control takes good stewardship. This video details how farmers can prevent weed resistance.

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[00:00:00.000]All right we learned in part two that weed populations don't give up. That
[00:00:07.560]genetic variation can exist in weed populations and the way farmers apply
[00:00:12.960]selection pressure can cause those weed populations to evolve and become
[00:00:17.360]resistant and the farmer encounters a situation where a problem they didn't
[00:00:22.200]used to have they now have. And so in part three let's take a look at what
[00:00:28.260]farmers can do to be better stewards of herbicide technology it really isn't any
[00:00:33.600]different when it comes to farmers use of herbicide technology as it is with
[00:00:39.780]doctors' use of antibiotic technology if you use it in the right way it can be a
[00:00:45.600]useful tool for a longer time period for people to benefit from and that's what
[00:00:52.180]the general public is interested in if these herbicides have advantages if
[00:00:57.480]they're safe for the farmer to use, effective in helping them can control
[00:01:01.980]weeds, and they can produce their crops on a more reliable basis. If the
[00:01:07.380]herbicides are safe for the environment and safe for people then we want to keep
[00:01:12.900]those technologies available for farmers to use in the longer run so let's take a
[00:01:18.000]look at this idea of stewardship there are several ways farmers can can do their
[00:01:26.700]planning in order to minimize the chance that they're gonna impose selection
[00:01:33.420]pressure on weed populations one is to rotate crops. So you may have one crop
[00:01:40.920]like your soybeans for example that grow in a way that makes it very difficult
[00:01:47.940]for them to successfully compete with a certain weed and an alternative crop
[00:01:53.920]that the farmer can
[00:01:55.920]grow successfully may provide a big advantage in its ability to compete with
[00:02:03.460]the very same weed. So weeds that are successful with one crop may be far
[00:02:08.800]less successful the next year with a different crop. So rotating crops from
[00:02:14.460]one year to the next, and the Midwest farmers will often rotate soybeans and
[00:02:20.360]corn, and this practice has been successful
[00:02:25.140]over a long time period in helping keep weed populations off balance and keeping
[00:02:33.600]the weed populations at a more susceptible state and more controllable
[00:02:41.960]or less competitive with the crop that the farmer chooses to grow. However,
[00:02:49.000]because of the success of glyphosate herbicide in controlling weeds in one
[00:02:54.360]crop, biotechnology companies were motivated to apply this technology to
[00:03:00.660]other crops. So the same gene that could be designed to confer resistance to
[00:03:07.680]glyphosate by encoding a different EPSPS enzyme could be transformed into tissue
[00:03:16.860]culture cells of corn, insert into the corn chromosome, and clone plants could
[00:03:23.580]be derived from these tissue culture cells that had this herbicide resistance
[00:03:29.480]gene in all their cells and therefore could be used by plant breeders as
[00:03:33.580]parents and could be therefore successfully incorporated into any other
[00:03:40.940]corn hybrid that a farmer would want to grow so while the farmer could rotate their
[00:03:46.800]crops they could continue to use Roundup year after year because every one of the
[00:03:52.800]crops that they were growing could potentially have this herbicide
[00:03:57.340]resistance. So we see Roundup Ready cotton, Roundup Ready canola, Roundup Ready
[00:04:04.080]sugar beets, corn. There's a number of crops farmers might use that they would
[00:04:09.540]put in their rotations, but they could always use glyphosate herbicide and we
[00:04:13.920]learned the consequence of repeated use of just a single herbicide -- the weed
[00:04:19.320]population will evolve. So
[00:04:22.020]crop rotation can be helpful but crop rotation alone won't prevent the
[00:04:32.000]occurrence the rapid occurrence of herbicide resistance because what you'd
[00:04:36.860]be doing is applying the same herbicide year after year. So in addition to using
[00:04:42.600]glyphosate a better practice would be to couple that with a second mode of action.
[00:04:47.940]Here is glufosinate, an active
[00:04:51.240]ingredient in herbicide that also blocks amino acid synthesis, but it blocks a
[00:04:57.480]different amino acid synthesis process. So it can kill a weed, but it kills it in
[00:05:05.580]a different way. So if you have a population that you're trying to kill
[00:05:12.600]with either glyphosate or glufosinate, the weeds can only die once
[00:05:20.460]and so the selection pressure applied by one herbicide doesn't give them
[00:05:28.440]resistance to the second herbicide. So what will often happen when that occurs
[00:05:33.060]is you'll have some individuals that survive but they'll survive primarily
[00:05:38.040]because they escaped and they won't necessarily have resistance genes that
[00:05:44.040]gave them a select advantage for one herbicide or over the other. So the
[00:05:49.680]populations gene pools change at a much slower rate and the second mode of
[00:05:57.460]action prevented the farmer from putting too high a selection pressure for success
[00:06:04.140]with the single herbicide, in this case glyphosate. So if they had coupled
[00:06:10.060]glyphosate with other modes of action the occurrence of resistance would
[00:06:15.640]have happened at a much slower rate. So the key to being able to successfully use this strategy
[00:06:23.850]is you've got to use it at the very beginning. You have to use two modes of action before the
[00:06:29.750]population evolves resistance to one of them. Because if they already have resistance to one,
[00:06:35.430]you're only really applying one effective way to control the weeds. So the weed population
[00:06:44.390]has to be managed using two modes of action at the very beginning of the weed control process.
[00:06:52.710]So a wise farmer will try to take that into account when they go about managing
[00:07:01.790]their weed populations using herbicide. So as we talked about, they'll avoid a sublethal
[00:07:08.210]dose by sticking with labeled rates. They'll avoid that single mode of action
[00:07:13.150]by using herbicides that block different critical functions. And they'll use these simultaneously,
[00:07:21.610]they'll use these at the same time. And then they'll avoid using the same crop year after year
[00:07:28.030]after year. So the natural biological differences between the way the crops grow and develop can
[00:07:34.370]be effective in minimizing or influencing the success of different weed populations.
[00:07:42.590]So rotating crops, using multiple modes of action, avoiding sublethal doses. When farmers
[00:07:49.530]apply all of these weed management tactics in their weed control program, they'll see resistance
[00:07:59.670]evolve at a much slower rate. That means these technologies are available for them to use longer.
[00:08:06.470]They benefit, and if these are safe technologies, effective technologies,
[00:08:12.390]the general public, the consumer, benefits as well.
[00:08:16.550]So the question is really an important question now as we look forward.
[00:08:23.570]There have been new technologies fairly recently discovered, developed, and commercialized
[00:08:30.670]that give farmers a new tool in weed control that they didn't previously have.
[00:08:38.010]Well, one would be a gene discovered in...
[00:08:42.010]a bacteria species that encodes an enzyme that degrades dicamba, a herbicide
[00:08:49.770]that farmers have been able to use to control broadleaf weeds, but have never been able
[00:08:56.190]to use it applied to a broadleaf crop like soybeans.
[00:09:03.670]And now with these dicamba-resistant soybeans, the farmer could apply these, just like they
[00:09:09.890]did glyphosate.
[00:09:11.970]The question is, how are they going to apply them?
[00:09:15.470]If they use them at the same time as they use glyphosate, but the weed population is
[00:09:23.130]already resistant to glyphosate, they're not using two modes of action, they're just using
[00:09:27.850]a single mode of action.
[00:09:29.550]So a farmer has to be thoughtful about what the status is of their weed population, what
[00:09:35.570]the herbicides are that they're able to use, and the best use of those combinations.
[00:09:41.930]Farmer's have to be more thoughtful in the future about the use of these herbicide technologies.
[00:09:56.650]They can do that when they combine the new technologies with optimal practice.
[00:10:00.710]The question that some people have is what's going to provide the best motivation for farmers
[00:10:09.110]to use wise technology?
[00:10:11.890]Can we as the public trust farmers to use these new technologies?
[00:10:16.790]Will they have learned from their past mistakes and want to avoid those mistakes going forward?
[00:10:24.310]Many people believe that's the best way to operate is to educate the farmer on what the
[00:10:29.670]situation is and then trust that they'll use wise practice.
[00:10:33.630]Other people believe that we're better off having some level of control over what the
[00:10:39.330]farmer does.
[00:10:41.850]Regulatory agencies need to play a role in that and not only in determining that a new
[00:10:48.370]product like the use of dicamba herbicide on a broadleaf crop is safe for the crop,
[00:10:56.610]safe for the environment, but also think about the optimal use of this technology to preserve
[00:11:05.870]the technology for use for a longer time period should the regulatory agencies play a bigger
[00:11:11.810]role in controlling how the farmer uses that technology? That's something that is
[00:11:18.830]considered by some of the consuming public and therefore it's an expectation that some
[00:11:28.530]people believe we should be applying to the regulatory agencies to companies and to farmers.
[00:11:35.870]How that will be resolved will we will we'll have the opportunity to see as these
[00:11:41.770]new technologies emerge and we and we see how they end up being used by farmers in their
[00:11:48.790]field. So this it gives us a good idea then why weed control is so important to farmers
[00:11:55.930]why the use of herbicides has been a useful tool for farmers to use in that quest to control weeds.
[00:12:04.150]But weed populations don't give up. They will continue to evolve and the
[00:12:11.730]rate at which they evolve depends upon how the farmer utilizes that technology. So all of these
[00:12:18.210]fit into the story of farmers, consumers, GMOs and the occurrence of super weed populations.

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Stewardship of Resistance

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