Late Season Soybean Diseases

Michael Sindelar Author

10/01/2020 Added

1 Plays

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Time is running out on the 2020 growing season! Join Michael and Tamra as they discuss late season soybean diseases and causes of dead patches in a field.

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[00:00:00.250](upbeat music)
[00:00:03.000]Welcome to CropWatch Podcast,
[00:00:05.400]a production on Nebraska Extension.
[00:00:08.019](upbeat music)
[00:00:12.690]Welcome to the CropWatch Podcast.
[00:00:14.550]I'm Michael Sindelar, Cropping Systems Extension Educator.
[00:00:17.740]Today I'm gonna be joined by Tamra Jackson-Ziems.
[00:00:20.700]And we're gonna be stalking about, soybean diseases.
[00:00:23.080]How are you doing today Tamra?
[00:00:24.800]I'm doing great, thank you.
[00:00:26.090]How are you?
[00:00:27.080]I'm doing good, doing good.
[00:00:29.850]Thinking across the state, we got a lot going on.
[00:00:31.820]We got some parts of the state
[00:00:33.080]that have gotten good amount of rain,
[00:00:34.810]And they're probably gonna have good yields.
[00:00:35.960]But then we've got other parts of the states
[00:00:37.490]that are in the drought.
[00:00:39.240]How is this gonna affect our soybean diseases?
[00:00:42.180]What we have right now,
[00:00:43.330]and what we can look forward to the future,
[00:00:45.310]or what we should be looking towards to the future.
[00:00:49.070]Feel free to start with, "Okay,
[00:00:51.297]"we've had rain, (Tamra laughing)
[00:00:52.247]"this is what you should be looking for."
[00:00:54.100]And then maybe we'll transition
[00:00:55.350]to what people who are in drought should be looking for.
[00:00:58.978](Tamra sighs)
[00:01:00.370]Things are really complicated right now.
[00:01:02.510]And part of that is, because of the varying conditions
[00:01:05.380]that we're dealing with around the state.
[00:01:07.300]And maybe even some of that is feel to feel differences.
[00:01:11.040]And that'll impact what's going on too.
[00:01:13.470]And so, in some of these drought areas,
[00:01:17.040]maybe they had rain earlier.
[00:01:18.960]And that might've been during a critical period.
[00:01:21.860]And so the thing right now is that a lot of people,
[00:01:25.180]are talking about patches of yellowing
[00:01:27.870]or dying soybeans out in the field.
[00:01:30.800]And unfortunately are making a lot of assumptions,
[00:01:33.490]that I don't think are correct.
[00:01:35.720]About what's causing that.
[00:01:37.700]And so that's where we're getting the most questions.
[00:01:40.110]And so right now the most chatter,
[00:01:42.710]seems to be about sudden death syndrome or SDS.
[00:01:46.710]And rightfully so,
[00:01:48.470]that's an important disease for us.
[00:01:50.640]And, that disease is one
[00:01:52.890]that we tend to see develop after you have
[00:01:55.810]had some rain during flowering.
[00:01:58.280]And thereafter, you start seeing leaves
[00:02:01.640]that are beginning to turn.
[00:02:02.970]You have a specific types of symptoms
[00:02:06.340]in those upper leaves though
[00:02:07.680]that I think are huge clues.
[00:02:10.160]And it really means people should get out,
[00:02:12.820]and take a look at what's going on in these spots
[00:02:15.220]while they're visible to 'em right now.
[00:02:18.160]And or call, whoever's helping you.
[00:02:20.860]Your crop advisor, to come out and take a look
[00:02:23.270]if they haven't been.
[00:02:24.730]So, SDS has these symptoms.
[00:02:27.560]We get yellowing
[00:02:28.640]and then eventually brown necrosis between the veins.
[00:02:32.800]And the vein stay really green.
[00:02:35.410]But you have a narrow window of time
[00:02:37.690]before those leaves die, and they defoliate.
[00:02:42.030]In addition, if you find symptoms like that,
[00:02:44.300]you really need to get some plants dug up,
[00:02:47.070]carefully with a shovel.
[00:02:48.990]Because both sudden death syndrome
[00:02:51.440]and brown stem rot, have similar leaf symptoms.
[00:02:54.940]But the stem symptoms, inside the stem,
[00:02:57.660]can be very different.
[00:02:59.500]And if you don't know what you're looking for,
[00:03:01.500]you should reach out, and get help.
[00:03:03.080]Send samples to our diagnostic clinic
[00:03:05.240]or call somebody in to help look at that.
[00:03:08.700]Because, we have really good resistance
[00:03:11.240]to some of these diseases.
[00:03:13.140]But it doesn't work if you pick
[00:03:14.830]or call it the wrong disease, right?
[00:03:17.630]And so for example,
[00:03:19.590]resistance to sudden death syndrome,
[00:03:21.420]can reduce disease severity by 80%.
[00:03:24.560]And that can mean a 12 to 15 bushel difference,
[00:03:28.570]between a resistant and a susceptible variety.
[00:03:31.010]So you wanna make sure and get that decision right.
[00:03:34.980]Right, you mentioned yellowing spots in the field.
[00:03:37.440]Are there other things
[00:03:38.580]that are causing those yellowing spots
[00:03:40.060]that maybe people should be, sending their scout out for.
[00:03:43.660]'Cause, maybe those yellowing spots
[00:03:46.130]or die off, isn't just disease.
[00:03:48.960]Exactly. Inspite of all this drought.
[00:03:53.360]People might be surprised to hear
[00:03:55.170]that we've had a little white mold show up too,
[00:03:57.730]if we're looking at diseases.
[00:04:00.310]You remember white mold.
[00:04:01.620]The initial infection takes place earlier
[00:04:04.000]in the season during flowering.
[00:04:05.890]Those flowers specifically are infected with that fungus
[00:04:09.000]and we were wet in some of those areas earlier.
[00:04:12.470]And, or else we were irrigating
[00:04:14.560]and maybe we had an environment under the pivot
[00:04:17.540]that was favorable.
[00:04:19.370]The fungus continues to spread.
[00:04:21.440]And now they're seeing the effects of that.
[00:04:23.760]Some of those plants are dying.
[00:04:25.230]And when you peel back the canopy and look closer,
[00:04:28.380]you might see cottony white fungus, growth on the stems.
[00:04:33.070]And it starts to make those little.
[00:04:35.940]It looks like rat droppings, it's nasty (vocalizes).
[00:04:38.620]Little survival structures called Sclerotia.
[00:04:41.620]And they they'll develop inside the stem,
[00:04:44.410]on the outside of the stem or in the pods.
[00:04:48.040]That's another dead giveaway that that's white mold.
[00:04:50.830]But then, we're getting calls about white mold or SDS,
[00:04:53.950]when it's not disease.
[00:04:55.920]And I think, when we see this patchy nature.
[00:05:00.250]How it's turning and, some of it's still really green,
[00:05:03.440]we've got others that are yellow.
[00:05:05.820]Gosh! There's a lot of factors in the field
[00:05:07.860]and the soil conditions like compaction,
[00:05:10.170]that can cause plants to die earlier,
[00:05:12.970]in drought conditions where they're not able
[00:05:14.890]to get up moisture effectively.
[00:05:18.370]You've probably think of other things, Michael, right?
[00:05:21.460]Well, I'm just thinking compaction,
[00:05:22.540]we had to what harvest falls and springs.
[00:05:25.670]So vehicle traffic compaction.
[00:05:27.580]that may not have been an issue during a normal year.
[00:05:31.070]But you throw it in a drought year.
[00:05:32.630]And, now that's showing up a little bit more
[00:05:36.090]that makes a lot more sense.
[00:05:37.510]And then just, topography.
[00:05:39.200]You might have your side slopes turning faster
[00:05:42.510]than your valley.
[00:05:43.740]So, depending on where your water settles,
[00:05:47.370]a lot of that makes sense.
[00:05:48.780]There's a lot of small variation that, can occur in a field.
[00:05:53.710]Especially if you're not used to the, a field.
[00:05:56.820]So. I think so too.
[00:05:58.050]I think this is important for us to talk about.
[00:06:00.770]And get people talking about it too.
[00:06:03.970]The other thing I was thinking about.
[00:06:06.860]We talked about SDS and brown stem rot.
[00:06:10.110]You know, we don't always see symptoms caused
[00:06:12.930]by a soybean cyst nematode.
[00:06:15.070]But sometimes, and then actually always,
[00:06:18.740]the soybean cyst nematode has populations that are higher
[00:06:21.960]in spots, randomly around a field.
[00:06:25.360]And if those plants are under stress,
[00:06:28.440]or if they have very high population densities,
[00:06:32.100]then it can cause symptoms.
[00:06:33.970]And I would guess when,
[00:06:35.340]you're having stressful symptoms like,
[00:06:37.170]some of these drought conditions we've had lately.
[00:06:39.550]Maybe that's the first spot you would notice.
[00:06:42.420]And so, if you've had, those spots,
[00:06:45.560]or if you've had SDS or brown stem rot,
[00:06:48.240]and maybe you haven't seen that before.
[00:06:50.530]I would especially wanna target those spots,
[00:06:53.290]in the field for a soybean cyst nematode test.
[00:06:56.240]Get your soil samples from that area.
[00:06:59.020]And for soybean cyst samples
[00:07:02.050]you know what, this is pretty easy.
[00:07:04.220]You can sample during soybean or corn or any other crop.
[00:07:08.000]Because the nematode stays in the upper eight
[00:07:10.570]to 10 inches of the soil.
[00:07:11.980]It's not going to move deeper,
[00:07:13.130]like some of the nematodes of corn.
[00:07:15.280]And so you can sample any time of year,
[00:07:17.978]until the ground freezes of course,
[00:07:19.850]and in any crop and get that tested,
[00:07:23.580]while it's still available for free right now.
[00:07:27.120]And so that can help you plan,
[00:07:30.129]for variety selection and other problems to deal with.
[00:07:35.060]You can manage diseases starting in the winter time
[00:07:37.750]at no extra cost.
[00:07:40.830]Good thoughts, that's something you can do
[00:07:42.550]while you're waiting for your truck to fill up.
[00:07:45.010]If you're on the side, hauling stuff to the town too.
[00:07:49.180]Absolutely that's--
[00:07:50.110]Especially if those places,
[00:07:51.070]are kinda marked out with a flag.
[00:07:52.450]That, you know.
[00:07:53.283]Okay, these are where I need to go take samples
[00:07:56.010]at the same time, put that time to good work.
[00:08:00.134]That's right. So maybe we should throw a probe
[00:08:02.760]and a box of bags
[00:08:04.900]and all of our trucks or pick ups
[00:08:06.990]and have that out.
[00:08:09.800]That's a really efficient use of your time.
[00:08:12.590]Oh, yeah. Sometimes time is the, our resource
[00:08:16.460]that we don't have enough of.
[00:08:20.770]Is there anything we really need to think
[00:08:22.090]about in some of our drier climates?
[00:08:24.570]I know I'm in an area where I drive 40 minutes one way,
[00:08:27.840]we've had enough rain.
[00:08:28.890]I drive 40 minutes another way,
[00:08:30.650]and I see the crop starting to turn really fast.
[00:08:33.690]And I started to see a lot of drought symptoms.
[00:08:37.688]That's a good point.
[00:08:40.060]All of these fungal diseases need moisture at some point.
[00:08:44.070]But there's at least one of them,
[00:08:45.870]that we tend to see more of, in those drought conditions.
[00:08:49.100]And that's charcoal rot.
[00:08:52.310]And, we don't spend a lot of time talking about it.
[00:08:55.810]But in those dry land corners or in counties
[00:08:58.820]in the Eastern parts,
[00:09:00.010]where we don't have irrigation especially.
[00:09:02.840]We can see some charcoal rot.
[00:09:04.730]And we've had some already this year.
[00:09:07.550]And so, what you'd look for
[00:09:09.680]is when you split those lower stems and roots open,
[00:09:12.710]they take on that silvery gray appearance inside.
[00:09:17.350]Well, that fungus creates millions,
[00:09:19.780]of these tiny black specks.
[00:09:23.234]It's supposed to look like charcoal dust,
[00:09:25.680]and that's why it got its name.
[00:09:28.220]But, that fungus is competitive even in drought conditions.
[00:09:32.800]And so, we tend to see it develop during these conditions.
[00:09:36.683]And its the drier spots of the field,
[00:09:38.900]like on those hilltops knobs.
[00:09:43.030]But also you can see charcoal rot in most of our crops.
[00:09:47.150]Not just soybean, but also in corn, alfalfa.
[00:09:51.680]And so, this is one that,
[00:09:54.694]it can affect several crops.
[00:09:57.160]And so crop rotation, not really that effective.
[00:09:59.900]This one's hard.
[00:10:01.800]Variety selection, maybe not that effective either.
[00:10:04.210]We don't really have good resistance to that disease.
[00:10:07.360]But knowing what's out there at least,
[00:10:10.290]you can be mindful of it.
[00:10:11.910]And, otherwise if it's something else,
[00:10:14.690]you can pick resistance for that sometimes.
[00:10:18.420]So you've talked a lot about picking resistance.
[00:10:21.370]I'm gonna guess that you can pick resistant a variety
[00:10:23.900]that's resistant to one disease,
[00:10:25.330]and then you may, have an issue with a different disease
[00:10:29.330]that, just 'cause it's resistant to one disease.
[00:10:31.590]that doesn't mean it's resistant to another.
[00:10:33.650]Is that why it's really important to know,
[00:10:35.130]what's in your field to make those selections?
[00:10:38.190]That's absolutely right.
[00:10:39.750]And so, I think the best example I mentioned earlier.
[00:10:43.620]SDS and brown stem rot can look very similar.
[00:10:47.170]And we have really good resistance to SDS.
[00:10:50.780]But if you called it SDS and picked resistant variety
[00:10:53.940]and it turned out instead you had brown stem rot,
[00:10:56.840]it's not gonna to be effective against that other disease.
[00:10:59.640]Unless it's resistant to both.
[00:11:01.670]And so this is a case where, it's important to look at
[00:11:05.420]the ratings, that your seed company provides,
[00:11:08.950]for these diseases.
[00:11:10.610]And that can be confusing too.
[00:11:12.740]You may wanna work closely,
[00:11:14.040]with your seed company representative and agronomist,
[00:11:17.070]to interpret some of those ratings.
[00:11:20.630]Many of those scales are one to nine
[00:11:23.170]or zero to nine.
[00:11:24.380]And, they're often opposing scales too.
[00:11:27.220]So if you're bouncing between companies,
[00:11:30.440]you gonna notice a one doesn't,
[00:11:32.660]it may mean good in one scale
[00:11:34.510]or it might be on the bad end and the other scale.
[00:11:37.260]And you don't often see,
[00:11:39.486]the extremes of the scales anyway.
[00:11:43.300]You're not gonna see a lot of ones and nines.
[00:11:45.990]Many of those scales are condensed.
[00:11:48.230]So you may see a lot of four or fives and sixes.
[00:11:51.420]But even being one number different,
[00:11:53.380]can make a big difference as far as, what you might expect,
[00:11:57.650]from that variety for that disease.
[00:12:00.310]And if you have a problem in your field,
[00:12:02.880]you see what's going on, diagnose it.
[00:12:05.360]I think record keeping is really critical.
[00:12:08.050]And not just managing it one year.
[00:12:10.140]Most of these pathogens over winter for multiple years.
[00:12:14.090]And it's important to continue selecting,
[00:12:16.670]resistant varieties for that problem year after year.
[00:12:22.400]Yeah, so it is very important,
[00:12:25.110]to know what you have Absolutely.
[00:12:25.943]So you can make sure that you make your best selections,
[00:12:29.910]and do it multiple years.
[00:12:31.870]Absolutely, and so,
[00:12:33.160]that brings up diagnosis and diagnostics,
[00:12:36.320]and the importance there,
[00:12:37.450]that, that's your first step in management.
[00:12:39.880]And submitting a sample
[00:12:41.170]to the diagnostic clinic may, cost you 10, 15, 20 bucks.
[00:12:45.640]It might save you a hundreds or thousands,
[00:12:47.610]for a variety, selection and disease management
[00:12:49.840]the coming years.
[00:12:51.610]And then, it lets you save some of that yield
[00:12:53.940]or protect some of your yield.
[00:12:55.608]You did mention earlier That's absolutely right.
[00:12:57.711]That some of those resistant varieties,
[00:13:00.030]will out yield the ones that are not resistant.
[00:13:04.420]They, it makes a big difference in disease severity.
[00:13:07.840]If you can knock back disease severity,
[00:13:10.800]and prevent those losses.
[00:13:12.860]It is a cheap way of managing diseases
[00:13:15.300]because, we don't have genetically engineered traits
[00:13:20.620]for these diseases.
[00:13:22.029]This is resistance that came about
[00:13:25.240]with traditional breeding practices.
[00:13:28.230]And so that's, usually the cost of those seed
[00:13:31.470]is no more than other comparable varieties.
[00:13:35.870]That's good to know.
[00:13:38.980]There other issues that we need aware of,
[00:13:40.830]at least on the disease spectrum,
[00:13:44.300]that may be coming up.
[00:13:46.410]Or is already here?
[00:13:48.660]You know, I guess I wanna put in a plug.
[00:13:52.050]One for, one last time for frogeye leaf spot.
[00:13:56.090]We are seeing frogeye starting to blow up in some fields.
[00:13:59.810]And its been there for a while now.
[00:14:02.480]And frogeye leaf spot,
[00:14:04.830]is a disease that you tend to see small lesions
[00:14:07.340]in the upper leaves first.
[00:14:09.380]This is a fungus that overwinters in that crop debris.
[00:14:13.400]And it's not new to us,
[00:14:15.330]but we've got some new developments in frogeye
[00:14:17.550]that people might not have heard about yet.
[00:14:19.940]And so you may have heard in other states,
[00:14:22.340]they've confirmed resistance,
[00:14:24.960]to the QOY or group 11 fungicides.
[00:14:28.470]That's the ones that we used to call strobilurins.
[00:14:31.560]And historically those are the ones
[00:14:33.780]that also worked the best.
[00:14:35.400]And so, we've sprayed a lot of strobilurins
[00:14:38.220]to manage frogeye leaf spot and other diseases.
[00:14:42.310]Or for the plant health effects that people are chasing.
[00:14:45.790]But the other thing
[00:14:46.950]that we know now is that, we're seeing resistance
[00:14:49.870]in a lot of states to that disease.
[00:14:52.270]And only just now in this past fall.
[00:14:55.390]When we collected samples and had them analyzed,
[00:14:57.960]we've now confirmed resistance in Nebraska too.
[00:15:01.570]And we collected samples from 10 counties, last year,
[00:15:06.180]and had those samples analyzed.
[00:15:08.890]And samples from all 10 of the counties that we sampled,
[00:15:14.170]came up positive for fungicide resistance.
[00:15:17.160]And, so that's not a,
[00:15:18.710]that wasn't a big survey.
[00:15:21.130]It wasn't comprehensive across the state.
[00:15:23.300]We were just trying to see if we could find it.
[00:15:25.820]And unfortunately, we not just found it,
[00:15:28.430]we found a lot in what we sampled.
[00:15:31.430]In fact, in what they collected
[00:15:34.220]from those specific samples, 111
[00:15:38.220]out of a 113, isolates of that fungus were resistant.
[00:15:43.120]So that's a 98% positive rate.
[00:15:46.350]And so we are continuing a more extensive survey now.
[00:15:51.150]And so we're collecting samples now,
[00:15:54.170]for further analysis here at UNL.
[00:15:56.520]We have a student, and support
[00:15:58.590]that we gratefully acknowledged
[00:16:00.170]from the Nebraska soybean board
[00:16:01.680]to look at that more in depth.
[00:16:03.420]And so if there's people with frogeye.
[00:16:07.030]And especially if they thought they had trouble
[00:16:09.740]managing it with a fungicide this year,
[00:16:11.810]we'd be interested in getting samples from your field.
[00:16:14.900]And talking to you about that,
[00:16:16.877]and looking at those more in depth over the coming months.
[00:16:21.150]All right, so are you just looking for people to go out
[00:16:24.310]and pick a few leaves and turn them
[00:16:25.720]into, like a local extension office,
[00:16:28.050]for them to make their way to you?
[00:16:29.630]Or whatever you looking for That would work.
[00:16:31.300]Is comprehensive study?
[00:16:33.670]That would work, you know.
[00:16:34.660]If, we got eight or 10 leaves
[00:16:36.530]that had frogeye leaf spot symptoms on them,
[00:16:39.070]that would be plenty for a field.
[00:16:41.720]And, let us know if a fungicide was sprayed on there.
[00:16:46.198]We, can get the fungus out better, if there wasn't.
[00:16:50.010]But we need to know how that fungus reacted,
[00:16:53.200]in the presence of the products too.
[00:16:55.300]So, there's a lot more work to be done on it.
[00:16:58.720]And we're just beginning that too.
[00:17:01.304]So, we appreciate the help.
[00:17:03.466]All right, and just to make it clear,
[00:17:04.798]you're not just looking for resistant samples,
[00:17:07.270]you're looking for
[00:17:08.439]frogeye leaves. Everything.
[00:17:09.580]Yeah. Yeah, everything. In general
[00:17:11.590]just if you have it
[00:17:13.230]and you're willing to donate a couple (Tamra chuckles)
[00:17:15.760]of samples, we'll take it.
[00:17:17.670]We'd be glad to.
[00:17:19.740]All right, well
[00:17:22.100]with that, we're starting to run a little short on time,
[00:17:24.420]and I'm sure there's still a lot of good information.
[00:17:26.690]Are there any resources out there
[00:17:28.160]that you would like to promote with what
[00:17:30.640]you were talking about?
[00:17:31.670]Any CropWatch articles or anything related to that?
[00:17:34.820]I sure would, and so this week,
[00:17:37.470]I'm working with colleague Melissa Bartels.
[00:17:40.460]County Extension Educator from Butler and Polk counties.
[00:17:43.710]And we're co-authoring an article
[00:17:45.670]to try to talk more in depth
[00:17:47.060]about some of those soybean diseases that may be causing,
[00:17:50.010]the mysterious yellow spots in fields.
[00:17:52.750]We've also got some historical articles in CropWatch too
[00:17:55.930]and, we have a lot of multi-state regional data
[00:17:59.630]and articles and publications,
[00:18:02.060]at the Crop Protection Network.
[00:18:04.966]That they can look at too
[00:18:07.170]and including, some of
[00:18:08.100]the most recent fungicide efficacy data
[00:18:11.470]that we are using for recommendations here.
[00:18:14.300]So, please let us know in Nebraska Extension
[00:18:17.330]if there's any questions you have,
[00:18:18.910]or if you're having trouble finding any of those resources.
[00:18:23.390]All right, Tamra.
[00:18:24.223]It's always great to have you on the podcast.
[00:18:26.720]Hope you have a great season.
[00:18:28.840]You too. Thank you so much.
[00:18:30.891](upbeat music)

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Late Season Soybean Diseases

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