Management of johnsongrass and foxtail species with post-emergence herbicides in white and yellow popcorn hybrids, 2020 Virtual Weed Management Field Day at South Central Ag Lab

Amit Jhala Author

07/13/2020 Added

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[00:00:06.860]Hi, I'm Samantha Isaacson.
[00:00:08.502]I am a research technician here
[00:00:10.960]at the University of Nebraska Lincoln.
[00:00:12.281]And I'm also pursuing my masters.
[00:00:14.790]And I've been studying Johnson grass here.
[00:00:18.131]And I've been doing a lot of driving around
[00:00:20.600]over the last three years looking at Johnson grass
[00:00:23.320]in different areas of Nebraska
[00:00:24.730]and into Kansas and in Missouri.
[00:00:26.500]And one thing I've noticed
[00:00:28.470]is that Johnson Grass pops up in a lot of popcorn fields,
[00:00:31.330]more than other crops.
[00:00:32.680]This is probably because there's not very many herbicides
[00:00:37.570]that you can use in popcorn
[00:00:38.782]that have strong action on Johnson grass.
[00:00:42.540]And so we see it persist and pop up
[00:00:44.330]in these popcorn fields.
[00:00:47.230]So Johnson grass is a big grassy weed.
[00:00:51.211]And one thing that makes it interesting
[00:00:52.960]is it has rhizomes and it can produce asexually
[00:00:56.180]through its rhizomes and sexually through its seeds.
[00:00:58.920]So it can be a problematic weed to control
[00:01:02.070]because of these rhizomes.
[00:01:04.030]Now, one good thing is that in Nebraska
[00:01:06.542]our winters are really hard on the rhizomes
[00:01:09.540]and they tend not to survive very well.
[00:01:11.801]And over the winter they'll tend to die off
[00:01:15.330]and then we don't see very many Johnson grass
[00:01:18.170]coming from rhizomes.
[00:01:19.130]We do see some, and here's an example of one.
[00:01:22.070]So, this rhizome came from another Johnson grass
[00:01:25.320]last year and then this year we have Johnson grass
[00:01:29.980]that sprouted from it.
[00:01:32.040]I'd like to take you on a tour of my research plot here.
[00:01:35.211]Right now I'm standing in front of my weed free control
[00:01:38.571]in my white hybrid.
[00:01:41.150]So as you can see the popcorn's
[00:01:42.610]looking pretty good right now, pretty tall.
[00:01:46.529]And we have pretty good weed control.
[00:01:49.930]And just keep this plot in mind when we're comparing
[00:01:51.659]when we're looking at my other plots
[00:01:54.130]and comparing the weed control.
[00:01:57.350]This is my untreated check.
[00:01:59.590]So this is my weedy control.
[00:02:02.197]This helps us understand what kind of weed pressure
[00:02:04.968]we're having in this field.
[00:02:06.790]And after we sprayed our herbicides in our other plots,
[00:02:09.890]I can go back and figure out what percent control
[00:02:12.538]these herbicides are achieving in the fields.
[00:02:15.488]We wanted to replicated a situation
[00:02:18.830]where a popcorn producer didn't have the opportunity
[00:02:21.099]to get a good pre-herbicide in
[00:02:23.526]and had a lot of grassy weed pressure.
[00:02:28.040]So there's situations like that.
[00:02:29.410]If it's rainy, the field's wet,
[00:02:31.150]you don't get the opportunity to get your pre in.
[00:02:33.010]Sometimes you can be in a tough spot
[00:02:34.419]where you need to have a strong post
[00:02:36.899]to help with your weed control.
[00:02:38.715]As you look in the plots, you'll see that these grassy weeds
[00:02:41.890]are very competitive with the popcorn.
[00:02:44.550]Popcorn is not as a competitive as a plant as field corn.
[00:02:48.397]And so weed control is so important that you do it right,
[00:02:52.330]that you do it well, so that you give the popcorn
[00:02:54.208]an opportunity to grow, get those nutrients,
[00:02:56.867]grab the sun, get the water, get the nutrients
[00:03:00.077]from the soil so that it can yield us well.
[00:03:04.660]So now where in our plots where I sprayed Armezon,
[00:03:07.530]which is a group 27 HPPD inhibitor.
[00:03:10.387]The active ingredient is topramezone.
[00:03:12.977]So as you can see this is a Johnson grass plant.
[00:03:15.819]We have a lot of bleaching going on.
[00:03:18.040]This is a really, this is a characteristic sign
[00:03:21.237]of something being sprayed with a HPPD inhibitor.
[00:03:24.750]We get that bleaching.
[00:03:26.130]I'll be interested to see,
[00:03:27.350]I'm not sure if this plant will die or not,
[00:03:29.480]or if it'll keep growing.
[00:03:30.499]I'll be following it over the next few weeks
[00:03:32.939]to see what kind of weed control
[00:03:35.670]we really see in these plots.
[00:03:37.260]So tomorrow I'll be taking bio mass
[00:03:39.648]to see how much, how many of the weeds survived now
[00:03:43.810]and again in two weeks I'll take another bio mass screening
[00:03:47.330]to see how many of the weeds survived.
[00:03:49.930]And then we'll compare it to our weedy controls
[00:03:52.946]and see what percent control we received.
[00:03:55.766]Overall it's doing okay.
[00:03:57.920]It's doing better than what it did last year.
[00:04:00.008]So it'll be interesting to see how it did.
[00:04:02.219]We're now in my spirit plots.
[00:04:04.608]This is a group two herbicide ALS inhibitor
[00:04:07.578]with active ingredients prosulfuron and primisulfuron.
[00:04:11.397]Last year this herbicide didn't do great for me.
[00:04:13.757]And this year I'm not seeing great activity
[00:04:16.340]in the grasses either.
[00:04:17.507]The Johnson grass and the Foxtails
[00:04:20.360]are still looking pretty good in these plots.
[00:04:23.477]We're now in my Accent Q herbicide plots.
[00:04:27.766]This is a group two herbicide
[00:04:29.968]with the active ingredient nicosulfuron.
[00:04:33.180]We don't see great activity on our weeds.
[00:04:35.537]You know, we still see a lot of Foxtails
[00:04:38.870]and Johnson grass that are doing very well
[00:04:40.590]in these plots so unfortunately
[00:04:42.130]I don't thing we'll have good control with the Spirit.
[00:04:45.940]Now we're in the Laudis plots.
[00:04:48.430]And this is an HPPD inhibitor with tembotrione
[00:04:51.850]as your active ingredient.
[00:04:53.590]Last year this was our best herbicide
[00:04:56.040]where we actually saw better weed control here
[00:04:58.150]than in the plots where I was trying to keep things
[00:05:00.150]perfectly weed free hoeing them out.
[00:05:02.550]It's a very good herbicide.
[00:05:03.779]This year I'm seeing pretty good control.
[00:05:06.120]You see those classic bleaching symptoms
[00:05:08.530]from your HPPD inhibitors.
[00:05:09.787]The one thing that I wish, I think if we had sprayed
[00:05:14.970]maybe a week earlier, we would see even better control.
[00:05:17.610]The weeds would've been smaller.
[00:05:18.877]We sprayed when a lot of the weeds
[00:05:21.030]were around seven inches, which is a little later
[00:05:23.650]than you would of liked to have sprayed.
[00:05:25.530]Sometimes in weed science we'll spray just maybe
[00:05:29.090]half a week later than would be ideal
[00:05:31.300]cause we like to see how our herbicides act
[00:05:34.360]when we're pushing them.
[00:05:35.680]When we're pushing them to their max to see
[00:05:37.747]how well they can do even in bad situations
[00:05:40.970]where the weeds are a little bigger
[00:05:42.210]than we would have liked them to be.
[00:05:44.750]We're now in my beacon plots.
[00:05:46.180]This is a group two herbicide, an ALS inhibitor.
[00:05:49.568]And this is with the primisulfuron active ingredient.
[00:05:52.387]We saw okay control here, not great.
[00:05:56.739]We're in our white hybrid plots
[00:05:59.320]and our yellow hybrid plots.
[00:06:00.298]It kind of looks a little worse.
[00:06:02.147]You see some of the, you see some tan necrosis
[00:06:05.888]on the grassy weeds, which is typical
[00:06:09.146]for your group two ALS inhibitors.
[00:06:13.300]We're now in my revulin q plots.
[00:06:15.400]This was my second best grass herbicide last year.
[00:06:19.370]It has both group 2 and group 27 herbicides,
[00:06:22.130]so nicosulfuron and mesotrione.
[00:06:26.148]This year it doesn't seem
[00:06:27.760]to have great control in this plot.
[00:06:29.470]You see some of that tan necrosis from the ALS inhibitors,
[00:06:34.860]but I'm not seeing any bleaching from the HPPD inhibitors.
[00:06:37.498]It'll be interesting to see how this does
[00:06:40.109]in the rest of the season and in my other plots.
[00:06:42.530]We always replicate our plots
[00:06:44.309]so that we're taking data
[00:06:45.990]not just from one area of the field
[00:06:47.240]but from four different areas of the field
[00:06:49.610]so that we can really know if what we're looking at
[00:06:52.390]is a result of the herbicide
[00:06:53.680]or a result of that area of the field,
[00:06:56.977]the environment in that area of the field.
[00:07:00.220]For the last three years Nebraska has grown more popcorn
[00:07:02.869]than any other state in the country.
[00:07:05.700]Historically we've traded that position
[00:07:07.360]back and forth with Indiana.
[00:07:09.309]But popcorn isn't grown evenly throughout the entire state.
[00:07:13.140]It's really centralized in a few counties
[00:07:14.877]around the sand hills.
[00:07:17.060]Holt, Lincoln, and Antelope county
[00:07:18.770]grow about half of the state's popcorn.
[00:07:21.269]Where as you can see on the map,
[00:07:23.398]the 11 other counties that are stared
[00:07:25.920]produce 93% of the rest of the state's popcorn.
[00:07:30.810]And as you can see this is really centralized
[00:07:32.898]around the edge of the sand hills.
[00:07:34.349]The sand hills are represented in green on the map.
[00:07:38.120]This is because popcorn does well with soils
[00:07:41.660]that have some sand in them
[00:07:42.730]because it allows the soils to drain well.
[00:07:46.190]So in conclusion, today I've showed you
[00:07:48.370]a lot of really weedy, grassy plots.
[00:07:50.757]And really what this tells you is that
[00:07:53.450]relying on a post herbicide for grass control in popcorn
[00:07:57.330]really isn't a good option.
[00:07:59.400]Your best option is to use a good pre herbicide
[00:08:03.509]with strong activity in grasses
[00:08:05.960]because right now we really do not have
[00:08:08.780]a strong post herbicide with strong activity in grasses,
[00:08:14.600]especially in Johnson grass and in Foxtails
[00:08:17.020]for use in popcorn.

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Management of johnsongrass and foxtail species with post-emergence herbicides in white and yellow popcorn hybrids, 2020 Virtual Weed Management Field Day at South Central Ag Lab

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