Soybean Seedling Diseases

Michael Sindelar, Nebraska Extension Educator with Tamra Jackson-Ziems, Extension Plant Pathologist Author

04/26/2019 Added

2 Plays

Description

On this week’s CropWatch podcast Michael Sindelar is joined by Dr. Tamra Jackson-Ziems for a discussion on soybean seedling diseases. The podcast provides listeners with what to look for when scouting for a seedling disease, how to manage Pyhtium and Phythophthora, and resources to use in making disease management decisions. The podcast also addresses strategies for controlling soil borne diseases in general.

Searchable Transcript

Search:

[00:00:00.329](uplifting music)
[00:00:02.950]Welcome to CropWatch Podcast,
[00:00:05.400]a production of Nebraska Extension.
[00:00:12.130]Welcome to the CropWatch Podcast.
[00:00:13.630]I'm Michael Sindelar, a cropping systems extension educator.
[00:00:16.670]For today's CropWatch Podcast,
[00:00:18.870]we'll be talking about soybean seedling diseases.
[00:00:22.420]I'm gonna be joined today by Dr. Tamra Jackson-Ziems.
[00:00:26.800]Tamra, would you like to introduce yourself
[00:00:28.380]a little bit more and what your role at the university is?
[00:00:31.280]Absolutely.
[00:00:32.810]I've been at the university now for 14 years
[00:00:35.670]in the position of extension plant pathologist
[00:00:39.110]with responsibilities for corn diseases,
[00:00:41.950]more recently for soybean diseases too.
[00:00:45.730]And so I have statewide responsibility
[00:00:47.940]and enjoy working with all of our producers
[00:00:49.800]and crop consultants and ag business representatives.
[00:00:53.550]So we're talking about soybean seedling diseases.
[00:00:57.000]Did our problems or the problems
[00:00:58.620]that we'll be facing this year, did they start this year,
[00:01:01.020]or are we inheriting something from last year?
[00:01:04.650]There's probably a little bit of both.
[00:01:06.980]That's a complicated response.
[00:01:09.600]But there's a few things going on.
[00:01:12.250]In the last several years,
[00:01:13.590]we've probably had a few more problems
[00:01:15.820]with some of our seedling diseases,
[00:01:18.160]a few in particular like Phytophthora
[00:01:20.840]that really require some attention from us year after year.
[00:01:25.660]But this past year there were some particular problems
[00:01:29.290]during the growing season, especially during the fall,
[00:01:32.460]that actually impact us for this year.
[00:01:34.830]And so namely, there were some late season diseases
[00:01:38.410]that developed because of the extended cool wet period
[00:01:42.250]that we had during our growing season,
[00:01:45.330]and also that in other states
[00:01:47.800]where most of our soybean seed are produced,
[00:01:51.170]like in Iowa and Illinois.
[00:01:54.670]And because of the problems they experienced,
[00:01:56.890]we want to take some precaution this year
[00:01:59.050]for our own soybean seed to make sure that our producers
[00:02:02.120]don't experience additional problems this spring.
[00:02:06.010]What are we looking for, or what can we do,
[00:02:09.700]as you said, taking extra precautions with our seed?
[00:02:12.710]What do we wanna start out with seed-wise?
[00:02:14.660]I know maybe we're answering the question
[00:02:17.240]to something ahead of time,
[00:02:18.300]but sometimes it's nice to know right off the bat
[00:02:20.180]what step one would be.
[00:02:21.880]Absolutely, some of our viewers may have noticed
[00:02:25.470]that we had a CropWatch article come out in mid-February,
[00:02:28.700]I think on the 13th,
[00:02:30.560]where we talked about some early realization
[00:02:35.220]that we had some problems with soybean seed quality
[00:02:39.190]and germination rates.
[00:02:40.880]That information came to us
[00:02:42.640]from the Nebraska Crop Improvement Association,
[00:02:45.610]as well as the Illinois Crop Improvement Association
[00:02:49.080]where they released data showing
[00:02:51.290]that soybean seed germination rates were reduced
[00:02:55.420]compared to what you might normally see
[00:02:58.260]in some of those years.
[00:02:59.900]Now, some of that was the result
[00:03:01.750]of the diseases I mentioned earlier
[00:03:03.580]that came late in the season last year.
[00:03:05.880]For example, Phomopsis seed decay.
[00:03:08.200]We see a little bit of that every year,
[00:03:10.090]but in 2018 there was quite a bit more of it.
[00:03:12.830]It was more widespread.
[00:03:14.800]And unfortunately the pathogen
[00:03:16.880]that causes that can be seedborne,
[00:03:19.550]and it can affect quality in seed the following spring.
[00:03:23.990]And so that's something in particular
[00:03:26.180]we wanna make sure people are aware of.
[00:03:28.470]And although germination is not affected in all of our seed,
[00:03:33.820]there's a significant percentage that might be.
[00:03:37.220]And so for instance, as much as 70,
[00:03:40.460]excuse me, as much as 10% of our seed
[00:03:43.100]that was tested tested below 70% germination rate.
[00:03:47.670]And that would be important for our producers to know.
[00:03:50.900]And you can get that information right on the tag
[00:03:53.840]on your seed bag as an indication
[00:03:56.310]of what that seed lot tested at.
[00:03:58.980]And it is significantly less than what you were expecting,
[00:04:03.080]it might mean increasing seeding rate of that seed lot
[00:04:07.610]or considering a soybean seed treatment fungicide package.
[00:04:12.570]So what exactly would we be looking for early
[00:04:15.980]in the season, or what is conditions setting up for us
[00:04:19.380]to pay attention to and scout a little bit more for?
[00:04:25.292]A few things I think I would want
[00:04:27.570]to remind everyone about.
[00:04:29.000]And so it's important to consider the disease history
[00:04:32.950]that you've got in your field or fields.
[00:04:35.490]And it might not be the same in all of them,
[00:04:37.680]and it's important to know which disease
[00:04:40.650]or diseases you've had a problem with.
[00:04:42.990]And so for example,
[00:04:44.630]Phytophthora is probably the best example in soybean.
[00:04:48.510]Phytophthora is one of a couple of different types
[00:04:51.840]of pathogens that we call Oomycetes or water molds.
[00:04:55.700]And that means that they have to have wet conditions
[00:04:58.540]to become active.
[00:05:00.210]And the last couple of springs,
[00:05:02.290]we've had some pretty wet conditions,
[00:05:04.390]and thus we've seen more Pythium and Phytophthora.
[00:05:08.140]Well, in particular, Phytophthora can be especially damaging
[00:05:11.100]because it's not just a seedling disease.
[00:05:13.740]It can also infect older plants in the middle
[00:05:16.940]or even toward the end of the season and kill them.
[00:05:20.100]But management can start at the beginning
[00:05:22.500]or even before the season starts,
[00:05:24.270]and we are fortunate to have a number
[00:05:26.230]of different management strategies for Phytophthora.
[00:05:29.810]Phytophthora, for instance, we have resistance to that
[00:05:34.150]in our major soybean varieties that are available
[00:05:37.690]and resistance to specific races.
[00:05:40.820]And so for instance, you might have heard of Rps genes.
[00:05:44.160]That's specifically what we're referring to,
[00:05:46.550]Rps1c, Rps1k.
[00:05:49.600]Those are probably the two most common options
[00:05:52.470]for Rps genes.
[00:05:54.020]But they're not effective against all the races.
[00:05:56.840]And so they're also not effective immediately
[00:06:00.130]upon planting and germination.
[00:06:02.300]It takes a little bit of time, a few days to a couple weeks
[00:06:05.720]before that's going to protect the seed
[00:06:08.860]and the seedlings from Phytophthora.
[00:06:11.320]And so if Phytophthora's a really serious problem for you,
[00:06:13.800]you're also going to want
[00:06:15.360]to consider tolerance to that disease.
[00:06:18.410]And tolerance is similar to resistance,
[00:06:20.810]but it's not as effective,
[00:06:23.520]but it's effective against all the races.
[00:06:25.610]And so a combination of a resistant soybean variety
[00:06:28.280]with tolerance is probably your best bet.
[00:06:31.300]On top of that, though, we do have seed treatment fungicides
[00:06:35.200]that can do a good job against Phytophthora.
[00:06:38.660]Products containing active ingredients
[00:06:40.580]like metalaxyl, mefenoxam,
[00:06:43.040]or ethaboxam have been very effective against Phytophthora.
[00:06:47.700]But if you're going to go that route,
[00:06:49.720]just know that it'll take the higher rates of metalaxyl
[00:06:53.310]or mefenoxam to be effective against Phytophthora.
[00:06:57.610]With that said, those products that are effective
[00:07:00.670]against the Oomycetes are not effective
[00:07:03.040]against other types of soybean seedling diseases.
[00:07:07.020]And so the others that we might be concerned about
[00:07:09.980]like Rhizoctonia or Fusarium
[00:07:13.030]would require an additional seed treatment fungicide
[00:07:15.920]from a different class
[00:07:17.280]with a different mode of action to be effective.
[00:07:20.380]And much of this information is
[00:07:22.260]in our 2018 Guide for Weed, Disease, and Insect Management,
[00:07:27.070]and a couple of of those pages were highlighted
[00:07:29.440]and shared during that February 13th article.
[00:07:33.000]Looking at our seedling diseases that are out there,
[00:07:36.820]are there some that prefer wet warm conditions,
[00:07:39.860]whereas other ones require wet cold,
[00:07:41.660]or are there combinations,
[00:07:43.070]or are some of them all the above?
[00:07:46.280]Some of them are all the above, unfortunately.
[00:07:48.490]And so in general I think the cool wet conditions
[00:07:51.810]are probably higher risk than the warmer conditions.
[00:07:56.900]For instance, we know of several different Pythium species
[00:08:01.110]that infect soybean and corn too.
[00:08:04.260]We know now that some of those species
[00:08:06.250]actually prefer warmer conditions
[00:08:08.410]instead of cooler conditions, and others prefer it cooler.
[00:08:12.580]In general in the northern climates,
[00:08:15.860]we think that it's more common
[00:08:17.350]for the cooler favoring Pythium species
[00:08:20.760]to be the ones that we're dealing with.
[00:08:23.210]And so those conditions are especially ones
[00:08:26.370]that I could be concerned about,
[00:08:28.010]but anything that's going to impact
[00:08:29.900]or slow down the germination and emergence of our seed.
[00:08:34.260]And so I would keep that in mind
[00:08:36.680]and try to reduce overall stress to the seed
[00:08:39.600]to reduce the chance of seedling diseases.
[00:08:42.150]You know, one thing that I don't think I mentioned
[00:08:44.680]were the types of symptoms people can watch for
[00:08:48.000]for varied seedling diseases.
[00:08:50.210]And so the most common one would be symptoms
[00:08:54.043]that would impact plant emergence or germination,
[00:08:57.700]and so if you see skips in your stand at emergence.
[00:09:02.040]And that could happen with individual plants,
[00:09:04.680]or it could also happen with clumps in low areas
[00:09:09.180]of the field, for instance, where it was wetter longer.
[00:09:12.840]And if you see those skips,
[00:09:14.500]it's not too much work to take your spade
[00:09:17.210]or your shovel and try to dig where a seedling should be
[00:09:20.630]and see if you can find it and take a closer look at it
[00:09:23.140]and see if you have any evidence
[00:09:24.800]of rotted roots or discoloration
[00:09:28.320]that might indicate a seedling disease problem.
[00:09:33.260]Are there any symptoms that we should be looking at
[00:09:35.050]on our seedlings when they emerge for disease indications?
[00:09:39.420]Similarly, any discoloration or evidence of stunting.
[00:09:45.150]Or you might see wilting or discoloration.
[00:09:48.800]And the unfortunate part is some
[00:09:51.490]of those seedling disease symptoms are pretty fleeting.
[00:09:54.990]They're not gonna last very long.
[00:09:56.910]Some of them might kill the plant very quickly,
[00:09:59.670]and you might not have a chance to find them,
[00:10:01.340]so you may see a dead plant there in the ground.
[00:10:04.990]But not all seedling diseases necessarily kill plants.
[00:10:08.440]Some of those plants may survive.
[00:10:11.860]They may always be stunted and always be infected
[00:10:15.030]and might not compete the best versus their neighbors.
[00:10:19.450]And so I would watch for those symptoms
[00:10:22.040]and might have to make a judgment call
[00:10:24.660]if a large area of the field is affected.
[00:10:28.390]So that would be something like Phytophthora
[00:10:30.433]that may not be as obvious as a seedling,
[00:10:32.470]but you come back later in the season
[00:10:34.230]and you're starting to really see those symptoms
[00:10:36.370]throughout the plant and it makes it easier to diagnose it.
[00:10:39.770]Exactly, and there's really nothing else you can do
[00:10:42.650]later on in the season.
[00:10:43.780]We can't apply a foliar fungicide to turn that around.
[00:10:47.840]And you just need to make a mental note
[00:10:49.560]of which fields were affected.
[00:10:51.420]I really think it's a good idea to submit a sample
[00:10:54.830]to the Plant and Pest Diagnostic Clinic too for confirmation
[00:10:58.740]because many of the diseases we work with
[00:11:00.820]have very similar symptoms,
[00:11:03.030]and you wanna make sure that you know which one
[00:11:05.040]so that you can make careful selections
[00:11:07.390]of your soybean varieties,
[00:11:09.488]and that'll mean better management in the future.
[00:11:13.510]So how would rotation work in managing this disease?
[00:11:18.430]Knowing that the majority of producers here
[00:11:20.830]do a two year rotate between corn and soybeans,
[00:11:24.090]is rotation an answer?
[00:11:27.200]Well, for most diseases and most pests in general,
[00:11:30.370]we do recommend crop rotation.
[00:11:33.110]Unfortunately, the pathogens that cause seedling diseases
[00:11:36.900]are those that are soilborne, though.
[00:11:39.240]And all of them have some special spore stage
[00:11:43.600]that is a survival structure.
[00:11:45.690]It may have a thick wall.
[00:11:47.530]But it's meant to help them survive harsh conditions
[00:11:51.500]like drought and even predation
[00:11:53.740]by some invertebrate species.
[00:11:55.590]And so in general, these pathogens are gonna outsurvive
[00:11:59.893]whatever rotation that we have for them.
[00:12:02.110]And in fact, some of them can infect both corn and soybean
[00:12:05.740]or some of the other common crops we would rotate with.
[00:12:08.800]So rotation is not usually gonna be
[00:12:10.710]that beneficial for seedling diseases.
[00:12:13.540]It would also be a good idea
[00:12:15.650]to consider other ways of reducing stress
[00:12:18.380]that people might not have thought of.
[00:12:20.270]We know now that herbicide injury can actually predispose
[00:12:24.450]some of these seedlings to seedling diseases,
[00:12:26.910]and so there is a complex interaction there
[00:12:29.550]that we're just beginning to understand,
[00:12:31.870]as well as a potential impact
[00:12:33.980]on soybean cyst nematode on other diseases.
[00:12:37.570]And we knew that for sudden death syndrome, for instance,
[00:12:40.620]but it's becoming more evident
[00:12:42.440]that soybean cyst nematode can impact seedling diseases,
[00:12:45.740]and so making sure you select resistant varieties
[00:12:48.510]for SCN too may be important.
[00:12:51.737]So this would be another good year
[00:12:52.590]since the Soybean Board did fund the testing
[00:12:55.870]for soybean seed nematode
[00:12:57.910]that if you have a field that's spotty
[00:13:00.120]or you're starting to see skips,
[00:13:02.160]it may be a a good idea just to submit another free sample
[00:13:04.600]to the diagnostics lab to see
[00:13:06.020]if you may have soybean nematode.
[00:13:08.130]Absolutely, especially if your yields are not hitting
[00:13:11.660]what you're expecting them to
[00:13:12.897]and you've ruled out other causes for that.
[00:13:16.190]This being free, it's about a $20 value per location.
[00:13:19.840]And we request that you submit those
[00:13:22.180]to the Plant and Pest Diagnostic Clinic there
[00:13:24.710]at UNL on East Campus.
[00:13:26.960]All right, anything else important?
[00:13:29.990]Yes, I guess lasting comment would be
[00:13:33.240]if you are making seed treatment decisions for soybean,
[00:13:37.960]consider that the diseases that you've had in the past
[00:13:41.730]and that some of your seed coming in
[00:13:43.840]may be carrying something
[00:13:45.100]that you haven't had before like Phomopsis.
[00:13:47.630]And if you're selecting a package of seed treatments,
[00:13:51.590]make sure that the one you select also has good activity
[00:13:54.400]against Phomopsis seed decay for 2019.
[00:13:58.700]And you'd look that information up in the--
[00:14:00.600]Guide for Weed, Insect, and Disease Management.
[00:14:03.500]And if you need to purchase one or more,
[00:14:05.170]those are available through the UNL Marketplace,
[00:14:07.940]I think for $15 online.
[00:14:10.630]Thank you for sharing that with us today, Tamra.
[00:14:12.900]Absolutely, I appreciate being on here.
[00:14:14.970]Have a great growing season.
[00:14:16.980]You too.
[00:14:18.259](uplifting music)

Soybean Seedling Diseases

Description

Searchable Transcript

Comments

Related Channels

Soybean Seedling Diseases

Description

Searchable Transcript

Comments icon comment

Related Channels

Comments