Identifying Soybean Seedling Diseases

Don Lee Author

05/16/2016 Added

84 Plays

Description

For more information visit the Oomycete Disease Diagnostics website: https://ge.unl.edu/oomycete-disease-diagnostics/

Searchable Transcript

Search:

[00:00:00.000](upbeat music)
[00:00:09.220]Hi, I'm Loren Giesler, extension plant pathologist
[00:00:11.425]at the University of Nebraska, Lincoln.
[00:00:13.783]Today, we're gonna talk about identifying
[00:00:16.103]soybean seedling diseases with a special emphasis
[00:00:19.183]on those oomycete diseases that fight Phytophthora
[00:00:22.703]and Pythium diseases that are favored
[00:00:24.403]by really wet conditions.
[00:00:26.143]The first thing we're gonna want to do
[00:00:28.093]when we get into a field situation is look
[00:00:29.763]at the overall field distribution,
[00:00:31.943]and that distribution pattern for our seedling
[00:00:34.663]stand problems are gonna be very pocketed,
[00:00:37.203]typically aggregated or pocketed around
[00:00:39.623]low spots in the field for our water liking
[00:00:42.383]or loving diseases that we see with our oomycete diseases.
[00:00:45.624]We're gonna see those pockets in various areas,
[00:00:49.303]typically a low spot, for example, here today
[00:00:51.983]we've got a terrace area in a field where you can see
[00:00:54.283]that oblong area where we had standing water
[00:00:57.365]at one point, that's gone today but you can see
[00:00:59.664]the result of that injury from that seedling
[00:01:02.323]disease that's present in this field.
[00:01:05.843]The other thing we're gonna want to do once
[00:01:08.005]we get into those specific pockets in the field,
[00:01:10.943]start to look at the margin of that pocket and the edge and
[00:01:14.223]how an individual row will see that distribution pattern.
[00:01:18.624]So typically with our seedling diseases, we're gonna see
[00:01:21.483]a good uniform stand and then in those pockets
[00:01:24.913]we're gonna see thinning in the row so we're gonna see
[00:01:27.495]a reduction of those plant numbers in a per-foot basis
[00:01:31.155]and then if it's really severe, we're gonna see areas
[00:01:34.095]where we have no seed emerged, where those plants
[00:01:36.816]have succumbed to that seed decay or rot in a pre-emergent
[00:01:40.397]damping off situation and depending on when it happened,
[00:01:43.477]we may see post-emergent damping off
[00:01:45.717]where we have pockets of even dead plants in the field.
[00:01:48.557]Now let's next take a look at a little bit closer
[00:01:51.176]at that individual plant and what type of symptoms
[00:01:53.897]and distribution we're gonna see on those.
[00:01:56.117]When we're looking at the individual row
[00:01:57.917]and we're looking at plants within the row
[00:02:00.316]and those individual plants, here we can see
[00:02:02.257]an individual seedling that's dead.
[00:02:04.614]That's a post-emergence damping off, didn't get all the way
[00:02:06.934]out of the ground and then actually, on the above ground
[00:02:09.274]plant parts, many times an indication of seedling disease
[00:02:11.956]are some of the cotyledons actually burning or wilting up
[00:02:14.595]early, before we even have a first trifolate emerging,
[00:02:17.896]we're seeing those cotyledons burning off,
[00:02:20.096]and even some marginal injury or browning and yellowing
[00:02:23.456]like we see on these plants.
[00:02:25.375]Nice indication that something could
[00:02:26.956]be happening below the ground.
[00:02:28.776]So the next thing we'll do is take that plant,
[00:02:30.656]and then we'll dig that up and look at
[00:02:32.076]the distribution of any symptoms on the root.
[00:02:33.976]So we're actually digging those plants up.
[00:02:36.015]We're just gonna take that and try to get that whole
[00:02:39.096]root system so we can try to see the actual
[00:02:42.236]distribution of what's going on below ground.
[00:02:45.136]So the first one we come into is our plant that's dead.
[00:02:48.176]Or has still got some life to it, but you can see here,
[00:02:51.856]on this one it's gonna not make it,
[00:02:54.316]and we've got some brown discoloration on lower root system.
[00:02:58.036]We've got some white roots left, but again,
[00:03:00.316]that plant's gonna die because it was killed
[00:03:02.255]here at the point right below those cotyledons,
[00:03:05.936]and that one will eventually die, and you can see
[00:03:08.196]on the tip even, some brown injury on the root system.
[00:03:10.836]These other ones where we've got cotyledon injury,
[00:03:14.116]if we start to look closer into those, we can look
[00:03:17.586]at a couple things here, we can see how much
[00:03:20.067]stress was on the plant from how deep it was planted,
[00:03:23.507]we can start to look for any distribution
[00:03:25.926]on those individual roots when we're going down in there.
[00:03:29.566]So we're not seeing a lot of fibrous regrowth.
[00:03:32.327]Again, this one we don't have any cotyledons left,
[00:03:34.746]so we know that that plant is gonna be slightly stressed
[00:03:38.467]below, and we can actually see a little bit in this case of
[00:03:42.627]some just light browning on the root system with that plant.
[00:03:47.737]So the next thing would be is if we could actually
[00:03:50.187]determine if this was pythium or phytophthora.
[00:03:53.247]So when we're actually looking inside,
[00:03:55.565]do we see any symptom inside that root system
[00:03:59.687]that would suggest a possible infection by phytophthora?
[00:04:03.658]Inside we can see we've got pretty clear and healthy
[00:04:08.457]stele in the center of the root right here,
[00:04:11.717]so it's not really looking too much like a phytophthora
[00:04:16.038]problem in this particular case, and these outer roots
[00:04:20.177]where we get that browning on the root system,
[00:04:22.717]those are breaking off, but many times we'll be able
[00:04:25.318]to just take that root system and peel that off.
[00:04:29.058]You can see here how we just maintained the stele
[00:04:31.517]of that root, the center, so when we just peel that back
[00:04:34.777]we're able to just take that off, which often indicates
[00:04:38.837]that we're dealing with a pythium on the outside
[00:04:41.637]that's just starting to lightly rot the outer part of that
[00:04:44.357]root system, and then that stele is maintaining intact.
[00:04:47.517]So our next step in identifying our seedling disease problem
[00:04:50.777]would be to collect a sample and go get that field diagnosis
[00:04:54.567]confirmed in a diagnostic center or diagnostic lab
[00:04:58.057]that could use either molecular or serological
[00:05:01.117]or even culturing methods to confirm which pathogen
[00:05:03.958]we think is the cause of our problem.

The screen size you are trying to search captions on is too small!

You can always jump over to MediaHub and check it out there.

Comments

0 Comments

Identifying Soybean Seedling Diseases

Description

Searchable Transcript

Comments icon comment

Related Channels

Comments