Herbicide Resistance

Leah Sandall Author

03/09/2017 Added

493 Plays

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This video discusses herbicide resistance development and management decisions to help prolong the onset of herbicide resistance in weeds.

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[00:00:00.836](upbeat music)
[00:00:09.835]Approximately 20 years ago in a formal presentation,
[00:00:13.297]I made the statement that Roundup will never look any better
[00:00:16.917]than it does the very first year you use it,
[00:00:19.927]and people might ask,"well, how on earth can you say that?"
[00:00:23.267]Well, it's because the population of weeds
[00:00:26.032]had not been exposed to Roundup,
[00:00:27.741]and it's made up almost entirely of sensitive plants.
[00:00:31.405]Once you start using Roundup, the second year you use it,
[00:00:35.104]there may be a few plants that survived the first treatment,
[00:00:38.892]reproduced, now they're more numerous in the field.
[00:00:41.741]You use it again and the proportion
[00:00:44.384]that are not controlled goes up,
[00:00:46.178]and so it appears that it doesn't look quite as good
[00:00:49.274]and it doesn't perform quite as well year after year.
[00:00:51.590]On top of that, I had the benefit of history.
[00:00:53.504]That's what happens with all other herbicides.
[00:00:55.332]That's what happened with Atrazine
[00:00:57.369]which was first commercialized in about 1960.
[00:01:00.018]That's what happened with Pursuit,
[00:01:01.933]and it's logical that that's what would
[00:01:04.415]happen with Roundup, and it did,
[00:01:06.533]and that's where we are today.
[00:01:08.490]The new GMO soybeans that are coming to the market
[00:01:11.219]are very similar to the Roundup Ready soybeans
[00:01:13.414]that are currently on the market in that they're taking
[00:01:16.018]an herbicide that would normally kill soybeans
[00:01:19.478]and now making it resistant to that herbicide,
[00:01:22.893]so we can spray 2,4-D or dicamba over the top of soybeans,
[00:01:27.689]which typically would kill a soybean.
[00:01:30.173]Soybeans are very sensitive.
[00:01:31.353]Now they have resistance and so soybeans are unaffected.
[00:01:35.750]Prior to the Roundup Ready crops,
[00:01:38.113]the herbicides that we used before that
[00:01:41.328]had important timing requirements.
[00:01:43.973]We had to treat very small crop and very small weeds.
[00:01:47.145]We used multiple herbicides, not a single herbicide,
[00:01:50.549]or a single mode of action, but several.
[00:01:52.607]Tillage was important because the herbicides alone
[00:01:55.378]generally did not provide adequate control.
[00:01:58.228]After Roundup came on the scene,
[00:02:00.628]growers pretty much abandoned those three practices.
[00:02:03.719]They just used Roundup and they weren't
[00:02:05.518]worried so much about tillage.
[00:02:07.523]They weren't worried about other herbicides,
[00:02:09.762]and they weren't worried about timing.
[00:02:11.265]Life was simple.
[00:02:13.507]So, primary concern with the new herbicide
[00:02:16.049]resistant technology coming out on soybeans
[00:02:19.899]would be ensuring that we safeguard or use them
[00:02:24.782]appropriately so that we have
[00:02:26.465]the use these technologies for a long period of time.
[00:02:29.220]So, we don't want to induce new resistance in populations
[00:02:32.966]similar to what happened with glyphosate.
[00:02:35.815]We want to take a tool that's really effective
[00:02:40.168]and we want to keep it effective for as long as possible.
[00:02:42.601]Where do resistant weeds come from?
[00:02:44.471]Actually, they were present in the field all along
[00:02:47.160]at very low frequency, very low population.
[00:02:50.663]When the herbicide is used,
[00:02:52.414]that resistant weed is not killed and the others are killed,
[00:02:55.802]so the sensitive ones do not produce seed.
[00:02:58.127]They don't reproduce.
[00:02:59.553]The resistant plant does produce seed,
[00:03:02.079]and repeatedly using the herbicide generation
[00:03:05.344]after generation results in the population
[00:03:07.531]changing from the susceptible to predominately
[00:03:11.237]nonsensitive or resistant weeds,
[00:03:13.235]and then we'd say the population is resistant.
[00:03:15.799]So, I think one of the really important ideas
[00:03:17.635]to avoid developing herbicide resistant weed populations
[00:03:23.137]is to not rely on a single herbicide
[00:03:27.210]or a single mechanism to manage all of your weeds
[00:03:30.827]'cause inevitably weeds are dynamic and they find ways
[00:03:34.857]around whatever it is that we're trying to stop them with.
[00:03:38.974]And so by using herbicides from different groups
[00:03:41.982]or different modes of action
[00:03:43.573]that target different sites within the weeds,
[00:03:46.745]relying on other mechanisms as well,
[00:03:49.514]like crop rotation or the use of cover crops,
[00:03:51.910]so anything we can do to diversify
[00:03:53.743]our cropping system and to target
[00:03:57.326]and look at preventing weeds from different angles,
[00:04:02.824]I think is going to be most effective.
[00:04:05.722]There's some feeling that the GMOs are somehow responsible
[00:04:09.381]for this development of herbicide resistant weeds.
[00:04:12.431]Well, that's not the case at all.
[00:04:14.677]The GMOs, Roundup Ready corn and soybeans and other crops
[00:04:18.101]are GMOs, allowing us to use Roundup on them.
[00:04:20.993]What causes resistance is the repeated use of the same
[00:04:24.246]herbicide year after year without incorporating
[00:04:26.903]other weed management techniques.
[00:04:29.188]GMOs made it possible for farmers to do that,
[00:04:32.200]but the GMOs did not cause resistance.
[00:04:35.829]What caused resistance was using Roundup repeatedly,
[00:04:39.010]and that's what we need to avoid
[00:04:40.559]if we don't want to have resistance.
[00:04:42.394]But diversification of the weed
[00:04:44.022]management techniques is the key.
[00:04:45.894]Don't rely exclusively on Roundup.
[00:04:48.746]So, how can we preserve new technologies as they come along
[00:04:52.411]so that we don't have this resistance problem?
[00:04:55.544]Again, we need to diversify our weed management techniques.
[00:04:59.166]Whatever new technology we're speaking of,
[00:05:01.325]don't rely on that exclusively.
[00:05:04.054]Include other herbicides with different modes of action
[00:05:07.067]where they can be used,
[00:05:08.879]a different crop, a different planting date,
[00:05:11.504]again, where it can fit in,
[00:05:13.105]tillage, where it can fit in.
[00:05:14.863]I realize there are constraints to using any one of these,
[00:05:17.895]but it is possible to incorporate at least more than one
[00:05:21.944]technique and diversify the weed management technique.
[00:05:25.370]So, in my opinion, I don't know that we can ever
[00:05:27.095]prevent resistant weed populations from occurring.
[00:05:30.882]I think the best we can do is to use
[00:05:34.755]all the information we have and use it as effectively
[00:05:37.603]as we know how to use it to slow it down,
[00:05:40.974]so that we have the use of these technologies
[00:05:44.098]and tools for as long as possible,
[00:05:46.418]I think with the hopes that we'll learn
[00:05:47.719]something new along the way.
[00:05:50.247](upbeat music)

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Herbicide Resistance

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