Join Emily as she talks to Bob about how he identifies Cercospora leaf spot in the field and in the lab.
This transcript has been edited for clarity.
0:22 Emily: Hi everyone, and welcome to Farm Sci-Ed, the show where we go into the science and education behind farming. I’m Emily Stine, and today we’re talking to Dr. Bob Harveson about cercospora diagnosis and what he looks for when trying to make a positive identification. So sit back, relax, and let’s go find out what he looks for.
0:37 Bob, can you tell me what cercospora looks like?
B: Well, it’s it’s a sort of an ash gray – it’s a lighter gray and they’re they’re oval to circular and they then they can coalesce and and really kill a large part of a leaf. They nearly always have some sort of a of a dark halo – dark brown to purple – that sort of thing. What you’re looking for, like with the hand lens, is is uh clear well they’re clear and they look kind of like cobwebs – you’ll see on the the lesion itself – you’ll see what looks like pepper pieces of little little pepper black and then you’ll see like the cobwebs and all that kind of stuff if it’s sporulating. If it’s not, then it’s kind of difficult to tell the difference.
2:27 E: What does cercospora look similar to in sugar beets?
B: Well I guess one of the things it can be is alternaria. Because that alternaria tends to be more circular and less oval than cercospora and it also doesn’t always have a border around it. There’s other several other diseases that foliar diseases like phoma that also can be confused if you don’t know what you’re looking for, and then bacterial leaf spot as well. When you have enough lesions that the bacterial leaf spot is starting to kill the the leaves, then that also can look like uh cercospora and been coalescing. And the reason that’s important to know is because the cercospora is the only one of this group that we really need to be concerned about. So if you if you mistakenly thought it was one of the other ones and made an application then you’re going to be wasting your money for that. Or if you thought it was one of the other ones and you didn’t make the application, then you also could take a hit from the pathogen that’s that’s damaging – or is cercospora.
2:27 E: How do you go about positively diagnosing cercospora infections?
B: You’re looking at the leaves you’re looking at it with with a hand lens, but honestly the only way to know for sure
in in most cases is to take it to the lab. And there’s just there’s a number of other things: you can plate it out, you can watch – watch, you know look at it under a microscope to see if you can see those spores, but it’s essentially you’re trying to make it sporulate so that you can identify it for certain with that. And sometimes it’s already doing that in the field sometimes it’s not.
2:57 E: And can you describe how you force cercospora to sporulate in the lab?
B: Something that’s called a humidity chamber is it’s just a paper towel that’s been dampened and put into a petri plate. And you just get a piece of the tissue that’s got the lesions on it, put it into that, close it up, and then it creates a really humid environment, which then in roughly 24 hours you can look at it again. It should be sporulating, then you can look at it in terms of that and and or you can put it put it onto media and let it grow out. And then in that way it would produce its uh the spores in that manner. Or you can also look at it directly uh with the with the microscope and see the spores themselves.
They they’re long and cylindrical, almost like a sword – a blade of a sword or something like that. It’s it’s very very long and thin.
3:50 E: How do the spores of Cercospora compare to the spores of other diseases?
B: Well it’s it’s hard to describe, but it’s – alternaria would to me look more like a club, you know it has a – it has a thin handle on it but then or more like maybe a tennis racket it’s got a bulbous end on one and then it’s got sort of like a handle on the other and with the cercospora, it would be cylindrical the whole way, like like a mop stick or something or broomstick.
4:20 E: What’s the next step after you have a positive diagnosis?
B: There’s not any kind of magic number, but I think in general, people look at this and say, “if you see three or more lesions on one single leaf then it’s time to it’s time to spray” or at least think about that. It also is important to know which part of the plant that – you’re not as concerned with it if it’s down in the lower part of the canopy as it would be up on the newer leaves, because that’s where the damage occurs. And and so then yeah because every time you look at that – you see three or four lesions, there’s probably more on the way that just haven’t formed yet.
4:55 E: Makes good sense to me! Well folks, today we talked to Dr. Bob Harveson about how he positively diagnosed cercospora in the field. We talked about what it looks like, what it might be confused with, and what he does in the lab to figure out if it’s cercospora or not. Join us next time as we go into detail on the other topics. Follow our twitter @TheFarmSciEd for updates on when new episodes are released and visit our blog at farmsci-ed.com for transcripts and other information. Have a good one!
Join Emily as she checks in with Jeff, Nevin and Bob on what’s happened with their projects over the course of July.
This transcript has been edited for clarity.
00:21 Emily: Hi everyone, and welcome to Farm Sci-Ed, the show where we go into the science and education behind farming. I’m Emily Stine and today we’ll be talking to Jeff, Nevin and Bob to find out what’s been going on over the month of July. So sit back, relax, and let’s go see what they’ve been up to.
0:41 So Jeff, how has your relay study been going?
Jeff: A couple big things going on in July in the relay study. One is we harvested the wheat. And so we brought a plot combine in, and the other big item is that western bean cutworms are flying and so those numbers are ramping up now. We’re still right around 25% emergence based on our predictive model and uh presently we’re catching hundreds every night. So we’ve got quite a collection – a couple thousand – more than a couple thousand western bean cutworms in a cage, laying eggs that we’ll use for various things within the relay study.
E: Have you run into any specific complications this month?
J: So the wheat harvesting relay this year is a bit challenging. Partly because in our research program, we share a lot of equipment, particularly expensive equipment like plot combines. And so you kind of get the equipment when you get it and this year we got the equipment a little later than we would have liked to, which meant that the dry beans were a little further along in maturity than they would normally be. What that means, is the the plants were bushier, a little bit bigger and they were starting to bud, so the flowers were just starting to form.
And so normally, last year, for example, we were able to get the combine a little bit earlier prior to – prior to budding and before the beans really had a chance to um to bush out that much. So what that meant was a couple challenges. One major challenge was because of the uh increased kind of growth, morphology, structure of the dry bean plants, they were more prone to getting run over by the combine. They get caught by the wheel and and you can knock a row down here or there. Fortunately we have really large plots, um but one thing we did do, um not only because of that sort of – what you could call “combine blight,” uh but also because they – as I mentioned – were starting to bud, some of them may have been starting to flower. That’s a fairly sensitive time for a dry bean plant. It’s more susceptible to injury at that time, mainly because those flowers can drop off. If you lose a flower, then obviously you lose a pod. You lose pods, you lose str – lose beans and so you lose yield.
So what we what we decided to do is we ran the plot combine through all the plots, regardless of whether or not the plot had wheat in it or not, just to make sure that all the treatments were treated the same – had the same potential for combine blight, if you will. So that was one challenge. We were successful in harvesting wheat off the top of the beans, the bean canopy was starting to get kind of close to the top of the wheat and there were a couple plants here and there that we clipped, and in fact there were quite a few growers and agriculturalists on Twitter that were pretty interested in us evaluating the clipped rows from the unclipped rows; partly because there’s some interest in the dry bean community and other growers, other crops as well that have similar growth habits, to try to understand what that clipping does to yield. There’s a bit of a debate on whether or not if you clip a dry bean at a certain time of the year if that promotes more branching, which promotes more flowering, so on and so forth, so we’ll probably take a few additional notes to try to account for some of that.
The other challenge was because the beans were already flower flowering, and we had to wait for the wheat to be harvested out of the relay plot. Before we could spray our first post – our post herbicide application, we were not able to apply uh herbicide in the relay plots, because the dry beans had begun to flower by the time we got the wheat removed from those plots. So so those plots will be uh not be receiving a post herbicide application. Benefit is, um in in treatments or in plots that are the relay plots where they have this cereal in it – like I, I think mentioned before – is there’s pretty good weed suppression in those plots as opposed to the conventional beans which had no residue at all – had a lot more potential for for weed development. So so we think that’ll that’ll work out okay, um but might require a little bit of hand pulling here and there.
E: Gotcha, well I hope you get some good data out of it anyway.
5:37 And Nevin, what about you? What’s been going on for you in the month of July?
Nevin: Well, July has has sort of been a continuation of June. June got very hot very early. I wouldn’t say extraordinarily hot, but it usually doesn’t get as hot as it does that early. So we were hitting triple digit temperatures uh earlier than we usually do, and July has sort of been a big continuation of that. So it’s been a very hot year and in June uh when we were planting our dry edible beans, we had a number of herbicide failures. Mostly we first noticed with our pre-plant burn downs.
So we have a few trials that are going into a cover crop or no-till and the products we use to kill that cover crop or the weeds that are present in those no-till studies, they just weren’t working. And um that’s a common experience among a lot of the people in the area. I’ve got some – I’ve been talking to my stakeholders that work at different uh agricultural service companies, different co-ops, and they’ve been having a lot of reports of herbicide failures. So that happened in June, but what we’re seeing though, is that that those failures this year um has has extended into our our soil applied herbicides, which are really critical for dry edible bean control and um we just have not been getting very good control.
And that’s, that’s a good thing actually for research. It’s not a good thing for farmers but uh we’ve got a few studies where we’re comparing uh group 15 herbicides so we’ve got Outlook, Dual, um Warrant, some of those products are labeled and dried, some aren’t. So we’re trying to see if there might be some possibility to expand the options available in dry edible beans. And we’re starting to see some separation, those products now in a normal year we wouldn’t see that separation. Everything would work pretty well but I think this year with just that – the higher temperatures um and also the increased irrigation that we need to put on to keep up with those higher temperatures, we’re starting to see faster degradation of the soil applied herbicides and we’re getting a little bit more separation in our weed control results between treatments and that’s good. You want these years, so that in normal year maybe there wouldn’t be a big difference but these extraordinary years or sometimes when you learn something.
E: Now if I’m correct, July is the month you do most of your data collection, right?
N: Data collection is pretty much what we’re doing in July. At this point, especially right now, it’s a bit later in July. We we have in the first couple weeks of July, we have sometimes – some later post-emergent herbicide applications in dry edible bean, but then we’re basically done with imposing treatments for the year. So what we’re doing now is maintaining plots by scouting for diseases and insects, sort of those lesser pests and try and keep up with the irrigation. That’s basically what July is.
But on top of that, we have data collection and right now what we’re doing is: depending on the trial we’re going out every week, every two weeks and we’re taking assessments. So visual assessments, we’re looking at the plots and just kind of making a note saying this this controlled um let’s say 70 percent of the weeds compared to the non-treated check where we didn’t do anything while this other treatment uh we’re looking at 80% control. And to kind of bolster those those ratings which are done visually, we’re also going in and taking some physical data uh and that’s mostly right now in the form of weed counts. We’ll do some more other stuff later on.
So we’re putting out specific quadrats – there’s, there’s my here’s my quadrat right there – and uh those are are laid out in the field and more or less a random method within each plot so that we’re not biased by where we’re putting it in in the plot. And then what we do is we we just count every couple weeks how many weeds are in that plot. And that gives us an idea of if there’s a difference in species response to certain herbicide treatments or if we’re seeing different types of herbicides come up at different times of year. so we can kind of track emergence throughout the year and uh we’ll be doing more measurements later on as we get closer. But that that’s been mostly what we’ve been doing.
We also have to in in certain studies we have a – what we call a hand weeded check, so in order to assure that we have a plot that has zero weeds in it. And we need the zero weeds so we know what the yield potential is of the dry edible bean crop and or other crops in absence of weed competition. We have to maintain those plots weed free and sometimes the best way of doing that is just going out there with a hoe and so we spend a lot of time this time of year going out, usually in the morning before it gets too hot, and we’re with a hoe and bent over just pulling weeds. And that’s a lot of what weed science is.
E: Hope all that went smoothly for you.
10:34 And Bob, how’s your cercospora and sugar beet study going?
Bob: Well, they’re doing fine. From a standpoint of a pathologist, it’s kind of disappointing. There’s not a lot of disease out there. We did inoculate a couple weeks ago, and the Spore-nado thing that we’ve been using, which which measures active movement of spores if they’re present, has not – uh has been zero. We’ve done this now for the three weeks, and uh there’s been no um cercospora found on the on the little discs that we see. It’s been – it’s certainly been hot and it might have been a little bit too hot, but it’s been high moisture in terms of the humidity – it’s been brutal. And it’s certainly been hot enough for that, but it’s not there. There’s apparently not any spores flying around. So we went out, and looked at that again – I mean I looked at it every week.
If we go back to the disease triangle, what we’re doing with the spore-nado is that we’re measuring to see if the pathogen is present and with the alert system we were seeing if the environment was conducive, and it’s just been off the charts from from the different sites that we have. But the fact that we’re not identifying any spores takes away that leg of the – uh of the triangle. So that the pathogen is not present so we’re just not getting any disease currently, even though we’ve tried to do everything: create a more humid microclimate, and sprinkler – overhead irrigation, it’s just not there.
And I don’t – I can’t understand why, but for some reason, they – we haven’t had a lot of evidence that the inoculation did anything. I’ve seen weekly reports of of the different sites, and they’ve really been high, which would suggest that the conditions were conducive for for disease to occur. But I have not heard of any severe outbreaks, so I – I don’t know if if that’s the case or not. But it’s that’s – that’s what we have.
E: Fingers crossed you get the results you need.
12:39 Well, folks there you have it. We talked to Jeff, Nevin, and Bob, and checked in on all of their projects and what’s been happening over the month of July. Unfortunately they’ve all run into a couple of hiccups, but for the most part things seem to be doing okay. Join us next time as we continue going deeper in their projects to find out more specifics about how and why they do the research they do. Until next time, don’t forget to like this video, leave a comment below, and subscribe to our channel for more updates. Visit our website at farmsci-ed.com for transcripts of all the episodes. Follow us on twitter @TheFarmSciEd for more updates and reminders about what we have going on. See you next time!
Join Emily as she talks to Nevin about what weed competition is and why managing fields for weeds is important.
This transcript has been edited for clarity.
0:21 Emily: Hi everyone, welcome back to Farm Sci-Ed, the show where we go into the science and education behind farming. My name is Emily Stine and today we’ll be talking to Dr. Nevin Lawrence about weed competition and how it relates to his studies as a weed scientist. So sit back, relax, and let’s go find out all about weed competition.
0:43 So Nevin, can you explain what weed competition is?
Nevin: Weed competition is uh simply the negative impacts on fitness to a plant caused by neighboring plants of another species. And this is most easily understood in the – in the terms of crops -with crops being competed against for resources by weeds.
N: Usually, when we talk about weed competition – uh weeds and crops are competing for water. So especially in – you know – dry land agriculture where you might not have enough water for optimal crop yield, when weeds are using some of that available water in the soil profile, you can have additional shortages to the crop. Nutrients, so fertilizer or just the nutrients that are naturally there in the soil, sunlight, and so you can you can have a tall plant that’s blocking some sunlight from reaching the bottom and that’s going to interfere with the optimal photosynthesis. And then sometimes also space is included in there as well – that they’re they’re running out of space because of the number of weeds in the field for a particular crop.
N: So competition – uh – when we think about it in terms of nutrient or resource competition – so they’re competing for a a resource that has to occur; you have to have a limited resource for for the competition to be to be happening. So if we think about planting a crop – let’s say corn – and you’re going to put in a starter fertilizer, well the corn is not going to be using all of that fertilizer right away. It’s gonna have to get to a certain height before it’s starting to need, let’s say if you’re doing a type of farming where you’re gonna be putting two applications of fertilizer on, there’s gonna be a point earlier on the season where it doesn’t need it yet, based on growth stage, that second fertilizer application.
So there’s there’s enough fertilizer – more than enough for for – let’s say that corn plant in this example, so we can imagine early on the season uh when we’re preparing the seed bed, everything’s just perfect and the the crops just coming up, there’s probably enough sunlight, space, water, and fertilizer for all the plants that are grown in the field – including the weeds. So we wouldn’t think that nutrient competition or resource competition’s occurring right early in the field. But we also do sometimes see yield impacts from early season weeds. But this isn’t generally considered to be caused by resource competitions. Instead it’s caused by something called the “shade avoidance response.”
N: Plants absorb certain wavelengths of light and they reflect other wavelengths of light. The reason why plants are green is because they’re reflecting green lights; they’re not absorbing that green light. And so, when a plant is is hit by sunlight and it it sends off certain wavelengths, neighboring plants can detect the presence of that particular plant based on the reflectance or changes in the way the wavelengths of of light that’s hitting them. So in particular, what happens is plants are able to change – detect changes in what’s called the red to far red ratio.
So red light is the light that we see, far red is uh red light that’s on a wavelength that we we cannot see. And so those changes in red to far red ratio, plants can detect that and those changes occur because of neighboring plants; either the light reflecting from the plant to the soil or to the neighboring – just directly to the neighboring plant. But they can detect that.
So plants can detect the presence of other plants nearby and just the simple act of detecting those other plants nearby, causes what we what we refer to as a “shade avoidance response.” So what they’re trying to do – the plants – is they’re once they know that “okay there’s another species nearby,” is they’re going to try to grow in a way to avoid being shaded.
They don’t want to be the lowest plant in that canopy, so they’re going to try to grow taller and so this is – this is called the shade avoidance response. And what that means is the plants will actually grow taller. We can also see changes in leaf morphology – leaf morphology. So the angle that they uh are going to hold their leaves up and so instead of being – let’s say – flatter, they’re going to be more upright. They might have smaller leaves because they’re putting more resources getting tall and all these changes that occur and not just with crops but also with weed species is in response to neighboring plants. They’re trying to avoid being shaded in the future from competition. uh
And what can happen though when we think about crops is uh when they’re putting these resources into growing taller and potentially smaller leaves, they’re going to be putting less resources into other things. Particularly when we think of a grain crop – so corn, soybeans, dry beans, peas, wheat – these plants which produce grain that’s harvested, less resources are going to go into that grain and so you might have a decrease in yield just because these plant – these weeds are nearby. And these weeds are nearby and this this response can occur when the weeds are very small and at a point where they’re not actually competing for resources yet.
And so what can happen in a farmer’s field, for example, is you might control the weeds when they’re very small so they emerge uh you’re you’re – through tillage or through an herbicide application – you’re gonna, you’re gonna kill all those weed species off. But they’re present for just long enough to alter the red to far red ratio reaching the crops. And that might trigger the shade avoidance response and lead to decreases in yield or yield potential even without any resource competition taking place.
7:10 E: Can you explain how the shade avoidance response ties into your research?
N: Yeah, uh so we we just, we’ve got a couple projects we’re looking at this. But one of them is – uh – we just finished, actually it’s it’s currently being prepared for publication uh from a former grad student – Clint Bierman and uh what we’re looking for is how long you need to keep the crop weed free to preserve maximum yield. And this is a long time old concept in weed science. It’s been done for a long time, and so what you do is you’ll start weeding a plot with with a hoe; you won’t use any herbicides and so it’s a very time consuming experiment.
But you’ll you’ll keep out of the plot for the whole season and then you might start – in this case it was dry beans – so when the dry beans hit the first trifoliate, so the first set of trifoliate leaves that come up will start weeding then. So we’re allowing a few weeks of weeds to be present and the next time we might start at the sixth trifoliate. And so what we see is as you let weed competition go on longer and longer and longer the yield goes down and that’s not very surprising.
But one thing that we did with this experiment is um in half the plots we had the same amount of weed-free periods so we’re removing these weeds by hand throughout the season for different lengths of time, but for half the plots they received what we call a soil active herbicide treatment at planting and so this was a a pre-crop emergence. So before the crop emerged, we put down an herbicide that’s active in the soil and it controls weeds after they germinate. And so that’s when the roots first emerge from the seed. But before those plants emerge from the soil, and so those plants never actually come out of the soil – those weeds never come out of the soil.
And when we compare the the weed free – so the whole season we we controlled all the weeds through hoeing when there was a uh the soil active herbicide applied, which only provided weed control for about the first four weeks of the year. That yielded higher than when we came in every – let’s say uh two to three times a week – and and controlled the weeds. And so we were literally going out there with a hoe three times a week, The plants never – the weeds never got taller than a quarter inch but just that small amount of weed emergence that would happen, let’s say between a Monday and a Wednesday, was enough to get a decrease in the yield.
Now it’s not a large amount, it might have been five percent of the yield that we we got from the season long weed free with the pre-emergent herbicide, but what we’re seeing is: having this herbicide that controls weeds while they’re germinating applied at planting actually provides some yield benefits just because of the shade avoidance response. So we’re preventing through the use of herbicides – um weeds – our crops from responding to the these changes in light quality um caused by the weeds being present.
And so that’s one example is that we’re actually seeing the use of soil active herbicides applied before crops emerge as preserving yield season long even when we remove all the weeds and the other treatments. And and this this is gets related to some other products we have. So um one of the things we’re doing right now in dry edible beans, uh again with our my graduate student Joshua Miranda is we have um we have – most herbicide – most programs in dry edible
beans you apply these soil active herbicides at planting, they wear off after about four to six weeks, and then uh you’ll apply – you’ll – once the weeds come up, you’ll apply an application of herbicides that control weeds that are that are emerged.
And these treatments, because of herbicide resistance no longer controlling uh one weed in particular – palmer amaranth – in our area, so we have to – what else can we do? So what we’re doing now is we’re applying these same herbicides that are applied at planting but we’re applying them – let’s say three to four weeks after the crop emerges. And so we’re overlapping these residual herbicides and so the goal is to never let that herbicide that’s applied at planting dissipate in the field where it’s no longer providing control. And so we have this overlapping residual herbicide that’s active in the soil and we can extend that control from four to six weeks at planting to maybe um six to eight, maybe even ten weeks after planting. And so what that means, is we’re preventing the weeds from ever coming up in in the soil. And that means we’re we’re probably not having actual crop competition when we use these post-emergent herbicides but uh that control weeds that already emerged, but those treatments may not be preventing the shade avoidance response.
And not only in dry beans but I’ve – I’ve personally – there’s a number of corn products out which are, have a high amount of activity in the soil and products like Acuron, Resicor, there’s a few others as well – I’m not trying to be particular in any herbicide brand – but but those herbicides, you apply them – uh let’s say at planting of corn – and then you can apply them at V4, the fourth collar stage on corn, and and basically you’re you’re you’re keeping that crop weed free all the way up until uh pretty late in the season without ever having to control emerging weeds. And so uh this is just another argument for why these soil active herbicides may be quite a bit better than herbicides that control weeds after they emerge, because we are not only preventing competition but we might be preventing the shade avoidance response as well.
13:03 E: Thanks Nevin. Well folks, today we talked to Dr. Nevin Lawrence about weed competition and the shade avoidance response and how those two concepts tie into his research here at the Panhandle Extension and Research Center in Scottsbluff. Join us next time, as we continue to look at Nevin and the other researchers’ projects over the course of the growing season. Be sure to like this video, comment below, and subscribe for more updates. Find us on Twitter @theFarmSciEd
and visit our website at farmsci-ed.com for transcripts and other information about this program. Have a good one!
Join Emily as she talks to Dr. Jeff Bradshaw about biological control and what impacts that has in his dry edible bean and wheat relay study.
This transcript has been edited for clarity.
00:21 Emily: Hi everyone, and welcome to Farm Sci-Ed, the show where we go into the science and education behind farming. I’m Emily Stine and today we’re talking to entomologist Dr. Jeff Bradshaw about conservation biological control and entomology, specifically in his relay plot study. So sit back, relax, and let’s go find out all about this.
So Jeff, can you explain what biological control is?
00:46 Jeff: So biological control is a part of integrated pest management. So it’s a tool – a tactic if you will – that’s used along with a number of other tactics in integrated pest management to reduce pest numbers, regulate those populations in a different way. So an alternative approach sometimes in a compatible way with other approaches, tactics, tools that might be used for for pest management .
01:13 E: What kind of strategies are typically used within biological control?
J: So generally speaking, there’s kind of three strategies to biological control. There’s classical biological control, which historically has involved and focused more on invasive species where you have a non-native insect – a pest whether it’s a pest of ornamentals or crops or other situations that a pest might arise in – that are introduced into the non-native habitat to that particular insect. And then you – the classical approach would be to go to the location where it’s native for the in the pest – in the case of the pest – you’d go to a location where the pest is native. And you would study and seek out the the natural enemies and maybe the parasitoids that might be highly specific to that species. And then there are a number of approaches then to introduce that that parasitoid, for example, into that new environment to try to see seek opportunities for control of that non-native species. So a classical approach is really focused generally on invasive species and trying to import those regulatory – regulating organisms into the environment.
Now the other approaches – augmentative biological control is where you have some understanding of what the pest’s existing natural enemy complex might be and you are releasing another natural enemy – such as a parasitoid – to augment or to increase the mortality of that pest through adding more natural enemies into the environment. And then conservation biological control is where you’re using different strategies or tactics in the environment through maybe changing the cropping system, rotation strategy, or some strategy that you might be using in the landscape – certain plantings of flowers or woody habitat maybe – that would provide habitat for natural enemies to to survive the winter or survive when the pest isn’t around. So three kind of general tactics um strategies that are considered in biological control.
03:31 E: What are the specific focuses you have within your study?
J: So currently, we’re looking at – we’re focusing on kind of two different areas of biological control. We’re looking at augmentative biological control with parasitoid wasps that attack the western bean cutworm and then we’re also looking at conservation biological control, primarily within the field, and looking at different strategies that we could use in cropping production systems that would bolster natural enemy populations; again specifically to attack western bean cutworm.
04:07 E: What are the differences between cover crop and relay biological control?
J: Relay cropping is a type of cover cropping. The main difference is termination time. So we’re looking at this study, our hypothesis is that if we have crops growing – we have something growing in the field before our main cash crop – dry beans in this case – that that
that that crop can provide habitat to natural enemies. So like I mentioned earlier, that would be a conservation biological control approach, and the main difference and the hypothesis we’re looking at is that the length of time that we have a crop in the field, in this case winter wheat, prior to our cash crop, dry beans, that length of time will influence the natural enemy population that is then available for the control of western bean cutworm. So in the case of the cover crop, we’re using a cereal winter wheat and we’re – we terminated that in late May, early June
as opposed to the release – relay system which is also using winter wheat as the cover, if you will, but instead of terminating it in June, we’re allowing that wheat to senesce naturally so that it will dry down and become ripe in around now – first week of July and so we think – there’s a possibility anyway – that that timing of when that winter crop is either terminated or senesces
naturally, will have an influence on the abundance and ecological function of those natural enemies in that system.
05:52 E: Can you share some of the arthropods that you expect to see within these systems?
J: Yeah, so the cover or relay crop in this case – uh winter wheat – is uh is a cereal and as a cereal, it can be a host to a number of aphid species like the Russian wheat aphid for example, and typically, those while – those insects can be very numerous and be economic pests in their own right in wheat. Generally that’s not often the case, at least in recent years, but they’re always present, so those aphids can serve as a food source for natural enemies so those would be lacewings,
ladybird beetles, big-eyed bugs, a number of different chewing or sucking insects that are generalist natural enemies that might attack aphids. We know they have a fairly large diverse diet and so they will also go after other pests.
So in the case of dry beans, what we’re hoping is of course, those those aphids are cereal aphids so they don’t go – dry beans aren’t a host for those aphids. So that’s a key aspect in the system that that helps make it work. Obviously, if the aphids in the wheat were pests of dry beans then we’d be setting ourselves up to a pretty bad situation. But in this case, again, the aphids aren’t compatible with the dry beans, but the natural enemies that they attract in
the wheat will feed on western bean cutworm eggs or thrips, either of which could be pests in in dry beans.
So our hope then is that we’ll have a early season establishment. Some of those aphid species for example, over-winter in wheat and so those can be available as a food source for those natural enemies as soon as they finish overwintering and start to come out in the spring. So that should give a lot of time for those natural enemies to feed, lay eggs, and build up those natural populations over time. And again, we would – our question is – that those populations might build up to larger numbers because they’ll have more time to develop in the relay system as compared to the cover crop system, at least under our conditions and the way that we’re looking at the system here.
And so timing wise, then we’re really kind of focused on the western bean cutworm – because it is a key pest of dry beans and as soon as – pretty close to when wheat senesces and typically is harvested in first or second week of June in any given year. That’s also really close to when we typically start to see one to five percent emergence of western bean cutworm and that can fluctuate given the year and the – you know the temperatures – and how they accumulate over the season. But that’s that’s kind of our goal is to try to target those natural enemies flushing off the wheat in high numbers to be present to uh – basically munch on those Western cutworm eggs that are are laid in dry beans.
09:03 E: You went into some detail on conservation biological control within your study. Can you elaborate a little bit on the augmentative biological control aspect?
J: Yeah, so the other part of our study we’ve looked at is augmentative biological control using Trichogramma ostrinae as a parasitoid of western bean cutworm eggs. And it was originally introduced into the US through a classical biological control program against the European corn borer. So that was a non-native introduced pest many years ago. And the biological control lab at Cornell University looked at this particular parasitoid wasp as a potential biological control agent.
Through the years, there had been some research, some science done looking at – um – the ability for that particular wasp to attack a couple other pest groups and we had done some early work looking at whether or not it would –
it found western bean cutworm eggs to be suitable, and we confirmed that they did at least in a laboratory. And then we did some field releases a couple years back, in – in cages to try to see if – in the field to see if there was uh any hope that there – you know if we showed it in a laboratory, but what you find in a lab doesn’t necessarily translate to what you find in the field. So we did sort of a semi-caged design in the field and kind of showed that yeah, it was still compatible host – the western bean cutworm eggs to trichogramma wasps there. So for a couple years, for three years actually, we did large-scale field releases on commercial dry bean fields and we used sentinel egg masses and sticky cards over – in every case a 10 acre square to look at the dispersal and dispersion of those wasps as well as their ability to attack western bean cutworms over that very large area.
And we’re still working on analyzing those findings, but generally we found that it seems like Trichograma ostrinae doesn’t really like Western Nebraska that much. It seems to work really well on the east coast, whether it’s green peppers or potatoes or sweet corn but for reasons we’re still sort of kind of fine-tuning what the next hypothesis might be as to why they might not work as well. But right now, we think it has to do with the environment, the climate that we live in is quite a bit different than than the east coast. If you’re not familiar with western Nebraska, it’s a semi-arid environment and semi-arid is definitely not how you defined upper New York state. So we think that probably plays a part in the success and why we had fairly low, fairly low parasitism rates.
12:12 E: Awesome, thanks Jeff. Folks, today we talked to Dr. Jeff Bradshaw about biological control and the different methods they’re using within the relay plot study. Join us next time as we go into more methods in these studies. Be sure to like this video, comment below, and subscribe to our channel for more updates. Visit our website at farmsci-ed.com for more videos and transcripts. Follow us on Twitter @theFarmSciEd for more information and for catching up on all those things you may have missed. Have a good one!
Join Emily as she talks to Dr. Bob Harveson about the Disease Triangle: what it is, why it matters and how important it is when determining Cercospora management.
This transcript has been edited for clarity.
0:21 Hi everyone, and welcome to Farm Sci-Ed, the show where we go into the science and education behind farming. I’m Emily Stine and today we’ll be talking to Dr. Bob Harveson about the disease triangle and what cercospora needs to flourish. So sit back, relax, and let’s go learn!
Bob: Well it’s a concept that’s been used by plant pathologists for a while and it just describes the the things that are that are needed for disease to occur.
So with the three points you would need a conducive environment, you would need a pathogen present and then a susceptible host. All three of those need to be going on at the same time or disease just isn’t going to occur.
1:06 E: Why is this something important to plant pathologists?
B: Well, that’s kind of what we do; is that we study the organism. We study what it needs to do so that we can potentially identify that point on the triangle which we can then access or we can take advantage of and and and reduce the disease.
B: Genetic resistance for the susceptible host and then we look at either fungicides or some other kind of process that would help remove or reduce the the pathogen. Or we can also modify the environment with the various types of cultural practices.
1:44 E: Now you’ve mentioned a couple methods of control that you use. Genetic resistance and and fungicide use are fairly understandable, but what is cultural control?
B: Well it’s it’s probably, with irrigation, okay, you need to uh limit the amount. I mean in other words, you need to find a nice amount that wouldn’t be overly wet. You know, just reduce it to – don’t let it get out of control with a a large number of – uh large volume of – don’t over water, I guess.
B: Cercospora needs – there are a certain amount of environmental conditions that it needs. It needs to have temperatures of 80 to 90 during the day, warm temperatures, and then at night something greater than 60. It also needs extended periods of leaf wetness, up to 10 to 11 to 12 hours and in order for the spores to germinate. So those those two factors have to be there at the same time.
2:45 E: How’s the alert system and the spore-nado catcher you’re using help you make decisions?
B: The alert system basically just tells you what the environment’s like. So when whenever you read those each morning, they would tell you a certain – based upon this algorithm in in a form – it would give you a specific number which which then would uh tell you whether the conducive the the environment was was conducive over the previous 48 hours, whether it was or was not. So that one concentrates on the environment. And the spore-nado was – is a structure or a mechanism for measuring if the spores are present or a relative number of them in that that respect. So that that gives you the the presence or absence of the pathogen and then the the alert system just tells you whether the environment is good enough for disease to occur.
3:45 E: Are there post harvest options for producers to use to minimize cercospora in the future?
B: Well, it would be helpful to – you know a lot of people don’t use the any kind of a cultivation – but yeah, if you can get rid of the residue then that would that would certainly help to reduce the the chances of disease the next year.
4:01 E: Well folks, there you have it. Today we talked to Dr. Bob Harveson about cercospora and the disease triangle, and how all three points of the triangle: the environment, the host, and the pathogen all play an important role in disease prevention. Join us next time as we go into detail on some of our other projects. Be sure to follow us on twitter @TheFarmSciEd and check out our website farmsci-ed.com for transcripts and other information. Have a good one!
Rather than talking to a specific researcher this episode, we thought it would be neat to see what parts of their research happens in the spring through June. Come join Emily as she talks to Jeff, Nevin and Bob about what’s been happening in their plots already.
This transcript has been minorly edited for clarity.
00:18 Hi everyone, welcome back to Farm Sci-Ed, the show where we go into the science and education behind farming. I’m Emily Stine and today we’ll be taking a little different approach, talking to Jeff, Nevin, and Bob about their current research projects and where they’re at in the month of June.
00:34 So Jeff, how has the relay study progressed over the course of June?
Jeff: Well, the month of June has been unusually hot and dry. So, we were able to get some timely applications in the study done, so we were able to in early June – well actually early May I should say – we got the herbicide banding done for the relay plots. So our strategy this year was to use an herbicide banding technique to spray out the wheat in the relay to create small beds for the for the dry beans that we’d plant in the relay treatments. Basically, in 30 inch centers we have basically a five inch band of wheat – three to five inch band of wheat – that’s dead that creates a – basically after the wheat dies in a month’s time, when it’s it’s very dead, there’s just a band left behind of, of no wheat, nothing growing. So then that creates a seed bed for our beans.
1:28 So we planted the beans then on June 1st, so about a month later. We used a GPS tractor for both of those so they could be locked in exactly where we wanted to plant the beans, which was not outside the banded seed bed but actually into the seed bed. So it was a little bit of trickiness with the equipment to get that lined up just right, but using the same planter and having some high precision equipment helped out that process greatly. So we got the dry beans planted on June 1st and again, it’s been pretty hot, so those beans came up really quickly. So we had emergence on June 8th; so about a week later they started popping up through the ground and we began our sampling process around then. I should mention we also fertilized the beans right after planting. So, in any plot that had dry beans planted in it, we applied a fertilizer to help the beans out. So right at that time, we – we sampled.
2:38 So our sampling plan continues on a number of different techniques. So we took wheat head sample – or we took wheat heads, collected them in the vials and shook them in alcohol and we’ll use the alcohol extract to look for thrips, both good thrips and bad thrips, to see what – what’s – what’s going on in the wheat heads since they can be a source, particularly for thrips. And as we’ve talked about before, since thrips can both be a pest for dry beans or beneficial, it’s important to account for those. We also, in all of the plots in each treatment, we set up pitfalls – pitfall traps. So basically holes with a cylinder in the ground and a cup that we use to collect ground roaming, ground beetles, or rove beetles, or other beneficial insects that are commonly found at the soil level that are collected in pitfall samples. And then we also took vacuum samples; so if you can imagine a leaf blower on reverse, that’s basically how we took the – we take vacuum samples. So we basically put a nylon stocking on the end of a leaf blower and uh – put it on the suck end of the uh – the sucky end (very technical term there) of a leaf blower, the intake of a leaf blower and then use that for a controlled period of time to take a standard sample. And we pulled those vacuum samples out of bean rows and the wheat rows – obviously if it was wheat only, there were no beans to sample, if it was beans only, there was no wheat to sample. But even in the relay plots where we obviously have both beans growing now and wheat, we made a concerted effort to just try to sample just the bean rows and just the wheat in those, to see if there might happen to be a difference between what we are vacuum sampling within the bean rows themselves and the wheat even within that in that relay treatment overall. And then of course, we’ll compare those samples across the different treatments to see what we’ve got. Other sampling techniques that are going on right now are sticky card sampling – so we have little three by five yellow sticky cards that have a tangle trap on both sides that we suspend in the canopy, which is pretty low to the ground right now, so we keep little – kind of wide – mesh cages around the sticky cards to keep debris from blowing into the sticky cards, leaves and residue that might be on the ground since the canopy’s so low, particularly right now. That’s our approach to keeping large debris out. But then those yellow sticky cards, the yellow color is really attractive to aphids and thrips, as well as some beneficial insects like minute pirate bugs and such. So we use those yellow cards as again yet another sampling technique. Many times when we’re sampling, we’re capturing the same insect with different techniques, but sometimes there are insects that are very specific to certain types of sampling techniques that you may or may not be aware of. So it’s good to use different tools – different sampling tools and strategies to just see if one of them works better than another to try to capture as much of the community as you can.
6:02 So basically right now, the past week, we’ve had um more than a couple days that have been in the high 90s to over 100 degrees with – um except for last night we had some cool weather and some rain that came through and that was that was pretty pleasant. But over the past week, we had some pretty high temperatures, very unusually high temperatures for June which isn’t unlike what a lot of the Midwest has experienced over this past month really is unusually high temperatures. So as a result, the wheat is finishing very aggressively, maturing along, and the beans are growing pretty aggressively as well. And also over the past month, we established soil sample soil sensors to establish soil moisture levels so we can try to keep on top of irrigation scheduling and so far that seems to be working, even though we don’t have really highly accurate soil sensors. They work well enough to just keep us out of the red. Last year we had some challenges, particularly in the relay plots not keeping up on enough soil moisture and so the beans would occasionally wilt. And you don’t want to get a crop to the point of wilting because that – sometimes you can wilt a little too much, and you actually lose plants as a result. So pleasantly, this June we’ve not seen any competition uh visually between the beans and the wheat. The wheat haven’t – the bean plants haven’t wilted due to the wheat competition.
7:42 E: Thanks so much for that update, it sounds like things are going really well out there. And Nevin, how has the first part of dry edible bean growing season gone?
Nevin: Well, dry beans are a pretty late planted crop in um well, everywhere, but the panhandle included. And the dry beans were planted last week in May, which is pretty typical. They’re usually planted towards the end of May, first part of – part of June and we we got all those in the ground by the – I think before June this year, which is pretty good for us. And there’s not actually too much going on at the moment as far as evaluating weed control. We have our pre-emergent herbicides we put on at the time of planting, or slightly before planting, or slightly after planting, and those usually give us between four to six weeks weeks of control and they’re still providing control now. Then, the date that we’re recording this is June 25th, so we’re still looking pretty good as far as weed control goes. So we haven’t done a whole lot as far as assessment and we’re not really seeing a lot of weed problems yet because those pre-emergent herbicides are still holding on.
8:52 E: Are there any specific tasks that you’ve been doing?
N: With the palmer density study, we have the palmer amaranth up and uh what we do is we went in – when I say “we”, it’s the royal “we”. It’s actually my graduate student Joshua Miranda. But he went into the study and what we have is we have six different levels of palmer density and we just kind of wait for that palmer amaranth to naturally come up and they came up right after dry bean planting this year. There’s no herbicides applied in that trial, and then we took different colored zip ties for each different population level – so we’d have yellow for a certain population, level in red, or you know so forth – and put zip ties around all these little tiny palmer amaranth plants and they’re going to stay there all year and then Joshua goes in two to three times a week and hoes out every single other plant that emerges. So it’s a pretty time intensive trial and we have to wait until those, those palmer plants emerge before we can do anything. But luckily, they came up early so we already have the populations established in the palmer interference study. We’re just going to keep hand weeding it all summer long and that’s really all we have left to do with that one until harvest time.
10:00 E: Have you had any abnormal challenges that you’ve had to deal with this last month?
N: The only challenge we’ve had, we have one study looking at different populations and row spacings of dry edible beans. So we have – it’s a very large trial; four populations dry edible beans and four populations – uh four row spacings and all those different combinations and that study was last we had planted. It was about a week later than the others and right as the beans were emerging, we got I think three – about a third of a – third of an inch – which isn’t too much, but that came down in about less than 10 minutes and so that that really washed out a lot of soil and we’re still the process of assessing the stand from that study, but it looks like certain parts of certain plots may have experienced some stand wash.
10:53 E: I know Jeff previously mentioned that he’d been facing some challenges with the heat. Have you been seeing the same problems in your crops?
N: The beans do fine with the heat. the beans are very – as long as they have enough irrigation water, they tend to do very well with warm temperatures and that actually helps speed things along for us so uh weed development crop development um how fast we sort of get through the season a lot of times depends on how warm it is and so when we have plenty of irrigation water available and this, this year, it’s been a good year for that. And we have a lot of heat units, the season just kind of comes along a lot faster so this has been a pretty fast season because we’ve had some pretty warm temperatures in early June but nothing that’s got in the way of doing research yet.
E: Well, I hope everything comes up just fine and things keep going the way they need to be going.
11:43 How about you, Bob, what’s been happening for you the first part of the season?
Bob: Okay well, the project began uh in the latter part of April, where we put down the pre-emergence herbicide and then it was planted on the third of May and then it emerged roughly two weeks after that. Then just last week, the post-emergence herbicide was then incorporated and then we’ve again continued to irrigate every week at least once a week and then put down about a half an inch each time. The next step with this is we will be inoculating the plots in about two weeks. We got this inoculum last year from infected plants just all over, dried them and then we’ll crush them up, mix them with talcum powder and then just sprinkle that onto the heads or on into the foliage of these plants. And then we will begin hopefully to use the forecasting tools that we’ve had to begin the study to begin the monitoring or accessing the information that we need for for both the presence of the pathogen and the environment, which is what we’ll be predicting.
13:00 E: Have the abnormal June temperatures been a problem for you?
B: It – well, it hasn’t really affected it to to date. I mean we were able to get up a nice stand at this point, uh because it was also the post-emergence about a week after that, it was cultivated. So that has taken away a lot of the weeds and I
imagine we’ll – we’ll have – we’ll end up putting another application of uh herbicide down sometime in August, I’m guessing. But, but the, this – the heat lately has not really affected I don’t think the the sugar beets because this is a last, uh an older, a disease that occurs at the end of the season. So we’re not really concerned about it right now.
13:42 E: Okay. What are you doing in the upcoming months?
B: Hopefully, we’re just going to inoculate and and hope that will enhance the chance for disease to occur. And then we’ll keep irrigating, keep trying to keep it wet and and see if that won’t uh establish disease a lot quicker.
E: Great! I hope that goes smoothly for you.
14:04 Thanks everyone. Today we checked in with Jeff, Nevin, and Bob to see how they were doing in their research projects. All three of them have their crops in the ground, we’re waiting for things to come up, and we’re kind of in a holding pattern. We’ve experienced an abnormally warm June and so things are happening faster than we expect them to and for us right now, that’s alright. Tune in next time to find out more specifics about the research projects. Be sure to like this video, subscribe to our channel, and leave a comment down below. Visit our website at farmsci-ed.com for transcripts and for other episodes you may have missed.
Join Emily discussing with Dr. Nevin Lawrence his work on palmer amaranth in dry edible beans.
This transcript has been edited slightly for clarity and grammar.
00:18 Emily: Hi everyone! Welcome to Farm Sci-Ed. My name is Emily Stine and today we’ll be talking to Dr. Nevin Lawrence, weed scientist at the Panhandle Research and Extension Center about his project working on palmer amaranth – a weed – and dry edible beans. So sit back, relax, and let’s go talk to Nevin.
00:35 Nevin: Hi, I’m Nevin Lawrence, weed scientist at the University of Nebraska Panhandle Research and Extension Center in Scottsbluff, Nebraska and I’m a weed scientist that works on many of the specialty crops and minor crops grown in Nebraska: dry edible beans, sunflowers, potatoes, alfalfa, sugar beets.
One of the major problems that we’re seeing now in the panhandle of Nebraska is palmer amaranth. And especially in dry edible beans, this is becoming a major issue for for farmers. Palmer amaranth is a troublesome weed across much of the United States. It’s in the news quite a bit; if you’re any way involved in production agriculture,
it’s something you’re probably aware of. But for Scottsbluff, Nebraska – for western Nebraska – it’s a fairly recent weed. When I first began my position here in 2016, not a lot of the farmers actually had heard of it, nor were they dealing with it. But just a few years later, it had expanded past Nebraska into Wyoming and it’s it’s now a growing issue in our area.
1:52 Palmer amaranth is a pigweed. It’s very similar to red root pigweed, which is the more common traditional weed out in the area, but there’s some key differences. One of them is palmer amaranth has a wider germination window than red root pigweed or the other pigweeds. So it emerges earlier in the season and it could be a problem throughout the production season. Along with that earlier emergence, it’s also more competitive: it grows faster, it grows larger, it tends to have more of an impact on on crop yield. Additionally, it produces far greater number of seeds than other pigweed species. In our research we’ve done, we’ve seen up to two-, three-hundred thousand seeds produced per plant. As you get more plants that number goes down, but a pretty consistent number we’re seeing is a hundred thousand seeds per square yard or square meter. It’s a pretty consistent number amount of weed seeds that can be produced from from palmer amaranth.
But kind of more of the issue why this is a problem, is there’s just not a lot of options to control palmer amaranth and that’s because our farmers rely quite a bit on herbicide options to control it. And palmer amaranth compared to other pigweed species, such as red root pigweed, prostrate pigweed, tumble pigweed, tends to have far more cases of herbicide resistance – similar to a water hemp – but both those species can have quite a number of herbicide resistance cases. And in the minor and specialty crops within the panhandle of Nebraska, sugar beets, dry edible beans, alfalfa, sunflower, we don’t really have that many herbicide options to begin with. So when resistance does show up in in the case of dry edible beans – this is why we’re mostly concerned with ALS resistance or group two resistance – when that resistance shows up within palmer amaranth, we run out of options very fast.
Not only do we we have issues with running out of herbicide options within the minor and specialty crops, but when we do rotate to a major crop like corn, for instance, many of the options that are available throughout the rest of the country aren’t really available in our area. And the reason for that, is rotation restrictions. Our soils are low in organic matter, very sandy, high pH, and a lot of herbicides tend to stick around longer than they would in other regions additionally because those herbicides are sticking around and we’re rotating these specialty crops. Some of our crops, such as dry beans and sugar beets are very sensitive to herbicides that can be used in corn and soybeans and so we can’t use those in our rotation. So we have just less options in general than a lot of the country and we end up having not many options to control palmer amaranth, both in in the dry beans and other minor and specialty crops but also in in the corn.
4:17 So I’ve been working on palmer amaranth as my major – one of my major focuses of my position since I since I’ve been here in the Scottsbluff or the Panhandle Research and Extension Center, I’ve done work in almost all the all the crops that we grow in the region. But in the past, in dry beans in particular, we’ve we’ve looked at some of the traditional herbicide options. So a traditional program here for weed control in the panhandle of Nebraska would be either using a pre-emergent herbicide – something like Prowl and Outlook – applied at planting or after planting, or you could use a PPI herbicide where you’re going to be applying something like Eptam and Sonolan in the soil, you’re going to be tilling that in to incorporate that before planting. And then both those programs if they need to, they’re going to follow it up with a post-emergence of something like Raptor and Basagram. Raptor is a group 2 herbicide, ALS inhibiting herbicide and Basagram doesn’t really work well on palmer amaranth to begin with.
And so, those post options just don’t really work in our research. In previous work, we’ve compared basically what’s better between those pre- and those PPI options and we found pretty consistently that the PPI herbicides – likely due to the the tillage that involved with the incorporation of those herbicides – can get quite a bit more control throughout the season. Sometimes it’s enough control that you don’t even need to apply that post-emergent herbicide and so those are some just kind of basic studies we’ve done. We’ve also looked at a micro-rate program that was developed by the North Dakota State University, where several different post options were applied at reduced rates at multiple intervals throughout the season and see if that compared, well to the conventional options. Now that program contains a herbicide called Reflex. Reflex is a great option for palmer amaranth and we we found that using the micro rate program, we’re reducing rates, making multiple applications, just really didn’t see any benefits compared to just a full labeled rate of the Reflex. Unfortunately, after that trial was completed and we got the results, the Reflex label was not renewed for our area due to herbicide carryover concerns to corn, and it’s not really an option anymore. So at the moment in the Panhandle of Nebraska, we don’t have any post-emergent herbicide options to control palmer amaranth. There – there are none. They don’t work well and all we have is these soil applied herbicides applied at planting generally.
6:41 And so what I’ll be talking about this season on Farm Sci-Ed is some of our ongoing research this summer, where we’re trying to control palmer amaranth with these limited options. The the first thing that we’re doing this year to kind of better understand palmer amaranth is we’re doing an interference study, where we are allowing different densities of palmer amaranth to grow with dry edible beans all season long and the idea for that is to provide farmers a great visual tool to know what the yield impacts are if if they have some palmer amaranth escape. And so we can say, “if the density is x number plants per per yard of row or per foot of row, this is the corresponding yield reduction that you can expect” and that helps us justify further grant opportunities for future research. But it also provides farmers an idea of what the the palmer amaranth induced yield loss would be and also what the seed production could possibly be in contributing to that soil seed bank the next year. That’s the first study we’ll be talking about. The second one this year, is the evaluation of split applications of Outlook. So Outlook is labeled for both a pre-application – so planted at or before the dry beans come up – and also as a post application. Outlook will not control palmer amaranth that’s already emerged, but it will prevent palmer amaranth from emerging. So what we can do is apply Outlook at planting, and then do a second application a few weeks later and try to get some residual coverage of palmer amaranth for several weeks. And so we may be able to expand a pre-emergent application which might provide control for – let’s say four to five weeks, maybe even six weeks and really extend that to six to eight to nine to ten weeks depending if all the conditions work out and that’s really our best option right now moving forward.
Additionally, there are other dry edible bean herbicides that are similar to Outlook: Dual II Magnum or Dual Magnum is one of them (Esmacholiclor) and that product is labeled pre-, but it doesn’t have that post emergence option labeled currently. So we’re evaluating that right now to see maybe is that something that could have a label expansion and be used similar to Outlook. And so we’re evaluating multiple group 15 herbicides – also Warrant and Zidua – to see if they could have potential usage in dry edible beans to expand our options for palmer control. Another study we’re doing this year is we’re just going to be screening a whole bunch of soybean herbicides to see which ones may or may not have tolerance to dry edible beans for palmer amaranth control, because there tends to be better options in soybeans than there are in dry edible beans. There may be some overlap, and there may not. We’re also doing quite a bit of research on cover crops and so we have both a trial looking at winter planted cover crops, which is not often an option in our area because by the time corn is harvested, we don’t have time to get the winter crop in. But it’s it’s worked in other areas, so we’re evaluating that. And then we’re also looking at a spring planted cover crop which is not a very common strategy in a lot of the country but there’s potential that we can get a cover crop planted in about March area and there might be enough time before dry edible bean planting to get suppression of palmer amaranth. And so we’re looking at those programs, and seeing how we can incorporate the cover crop with herbicide programs to have a nice broad slate of options for control palmer amaranth. And then finally we’re also looking at what options in corn work best for control palmer amaranth and bring more modes of action, more herbicide diversity into the program and still allow rotation that next year in the dry edible beans and that’s more of not necessarily a research project – we’re not going to be discovering anything new – but it’s an extension project that hopefully will provide farmers with some options where they can see what works, compare prices, compare how it looks in different field trials, and make an informed decision.
10:23 Emily: Well folks, there you have it. Today we talked to Dr. Nevin Lawrence about his palmer amaranth and dry edible bean studies and discussed the different studies he’s doing – specifically looking at how weed density influences plant growth and different herbicide options for weed management and dry edible beans. Don’t forget to like this video, and subscribe to our channel for more science and education behind farming. And leave a comment if there’s something you found interesting in this video! Be sure to visit us at our website at FarmSci-Ed.com, for more information and for transcripts of this video. Have a good one!
Join Emily as she discusses the concept of a relay cropping system with Dr. Jeff Bradshaw.
00:20 Emily: Hi everyone, welcome to Farm Sci-ed; the show where we go into the science and education behind farming.
I’m Emily Stine and today I’ll be talking to Dr. Jeff Bradshaw, entomologist at the Panhandle Research and Extension Center. We’ll be discussing his research on the relay system that he’s been working on with wheat and dry edible beans. So sit back, relax, and let’s go check out what he’s been up to.
00:42 So Jeff, can you explain to me what a relay cropping system is?
Jeff: So a relay cropping system is a method of intercropping, where you have one crop that’s planted into an existing crop and particularly in our case we’re looking at a cereal – a winter cereal, winter wheat – and then we plant dry beans into it – a legume – in the spring.
So the existing crop is then harvested first.
So winter wheat would be harvested before dry beans and we’ll harvest that off the top of the dry bean canopy essentially, and then we’ll come back in September and harvest those dry beans.
So typically, in these situations, we have often times – a legume is planted into into a cereal crop where you see these types of relay crop inter-cropping systems and part of that is because of their different plants. They don’t share necessarily the same diseases or pests or even weed control technologies and strategies.
01:44 E: And how does this differ from a cover crop?
J: Yeah, it does share some similarities with the cover crop. Some of the benefits of a cover crop as the name implies, is to provide cover at a time of the year where there normally wouldn’t be right. As opposed to just bare ground, bare soil that would have the potential to blow or to lose moisture and lose some of the other benefits that that a cover crop can provide including weed competition. Basically um, by having that cover present, the way that the relay cropping system is different than a cover crop is that you’re actually running that that early crop out to harvest. So that makes it different. And then in our case there’s uh timing of the crop that coincides with some kind of key pest development throughout the the season, as well as provide some benefits to the natural enemies that are in the environment. So if we, for example, have that relay cropping system established early similar to a cover crop but then as it matures, those natural enemies that are conserved in that relay cropping system can then emigrate out of the – of that cereal and into the legumes at a time, in our case, that would hopefully coincide with when when pests become more active. And so now, those predators can be available to to attack those pests – that’s the strategy anyway.
3:12 E: So when you’re growing in a relay system
what compromises do you have to make ?
J: Yeah, so there certainly are compromises as there are um in many cases in agricultural actions. So there is the possibility of reduced yield, so we’ve got – you know – competition between the two crops on any given plot of land. When we’re looking at that that relay system so they compete for really all the inputs that go to making a plant grow. So there’s competition with water, soil moisture, for example, there’s competition for nutrients, competition with light, and so all those become a factor to consider in this relay cropping system that could be trade-offs that need to be explored. And so ultimately, what we’re doing is trying to look at what would the balance of those trade-offs be? And from a whole cropping system perspective, are the trade-offs worthwhile, because they bring some other benefit down the line, meet some other goals for for the land manager and the agriculturalist or the producer.
4:19 E: Are there other benefits the wheat and dry edible bean system provide?
J: Yeah, so initially when we thought about this particular cropping system in our conditions out here in western Nebraska, initially you know, as an entomologist, I have a – I have a bug bias, sorry to say. But uh sorry not sorry. So you know, I did think about some of these relationships that have been shown in the literature between – you know – in regards to having a crop present earlier in the season. As I mentioned earlier, how they can help establish natural enemies earlier than they would otherwise be established in the field, and making them available later in the season in higher numbers where they can be more functionally relevant. But importantly, we also thought about the production system and what some – you know – our grower is mostly concerned with yield: the amount of grain that’s that’s harvested off the field, and of course the quality of that grain. And so we did, in thinking through this, think about the production aspects first.
And then it sort of dawns on you, as you think about a little more. “Like “oh that’s kind of similar to this,” “oh there may be some other side benefits to that.” So um those would include and specifically elements we think about dry bean production here in this part of the world, there’s a lot of interest in upright beans – upright dry beans. And part of that interest is because you can use a direct harvest combine, you don’t need the the additional equipment or additional passes through a field that you would need with a prostrate bean that’s grown along the ground. Or you have to cut it and windrow it and then come out and pick it up. So there’s these benefits with this direct harvest in terms of equipment: streamlining equipment, streamlining time that a grower spends in the field harvesting the grain; the trade-off historically with direct harvest is some challenges related to getting the pods high enough off the ground. Get them high enough off the ground, where the cutter bar can actually harvest a majority of the grain. So typically, we’ve seen that there’s, there can be a lot of variability depending on equipment and production practice and soil topography and and so on that can uh interact with with yield loss. But we see somewhere around 10% yield loss in direct harvest beans that are just a matter of the mechanical harvest process.
So in a dry bean plant – in the upright morphology –
we still see a lot of the dry bean pods hang below the cutter bar. You know, less than two inches above the ground and might even touch the soil surface so what happens is as the combine goes through, the cutter bar goes through, it clips all those beans that then can’t be taken up into the combine. They just fall shattered to the ground. So one of the things we thought about in this intercropping relay system was the attributes of the plant to grow a bit taller when it detects infrared light from surrounding plants or has uh light competition. So a dry bean plant will grow taller, the inner nodes would be longer, and the thought is then, those pods would actually be higher above the ground. So that’s one other aspect that we’re looking at strictly on the agronomic production side of things to see okay now we’ve got pods that are higher of above the ground, so even though if we have these trade-offs with – as I mentioned before – soil moisture, or nutrients, or light, we may see the benefit of actually recovering more more yield because we have a taller bean.
8:04 E: What does your research look like this year?
J: Yeah, so our aspect of the relay study – so we’ve got uh – we’ve got a bug side and a weed side of the study that we’re doing. And so, on the bug side of things, we’re specifically looking at the relationship between – um – well we’ve got four treatments that we’re looking at: we’ve got dry beans only, so we actually rototilled the plot and then planted beans; so really low residue, maybe a very conventional historic type of of bean planting from the
perspective of soil management, I guess
you could say of residue management. We have the cover crop approach which is – you know – winter wheat terminated around flowering.
Really, the the wheat is terminated at bean planting, so we plant the beans and we terminate the wheat crops so basically by the time the beans come up the wheat’s dying back.
So that’s our cover crop. Then we have a wheat only, so we have plots that are just left as winter wheat they won’t have any beans to try to look at the the competition – the the wheat competition side of things from just the wheat alone. And then, of course, we’ve got our relay treatment where in that case, we created very small beds for the beans to plant in – within – in rows within the wheat. And then and then planted the beans.
9:28 E: And what are you specifically focusing on within entomology and the relay cropping system?
J: Yeah. So with these four treatments we’re looking at specifically biological control and conservation biocontrol. So right now we’re – we’ve got pitfall samples, pitfall traps that we’ve got out in each of these plots for these treatments looking at ground beetles and other arthropods that would be roaming across the ground that might be influenced by these different treatments. Specifically looking at beneficial insects in this case, so there may be one management approach that seems to increase the number of functional species groups that are important for weed seed consumption, or maybe they’re important for predation of of pests later in the season, so we’re looking at those samples.
We also have sticky card samples – sticky card traps – that we have in the field to capture any winged insects, whether they be pests or beneficial and so we’re going through those counting a lot of thrips and aphids and as well as beneficial insects like big eye bugs and so on. Then we’re also doing vacuum sampling to again capture all the arthropods – pests and beneficials – that are actually within the wheat rows but then also within the bean rows even within a treatment. So in our relay treatment for example, we’re taking vacuum samples of the bean rows and then adjacent to those also. So we’re tracking that. We’re also taking sweep depth samples and we’re counting those. And when I say we, I’m – I’m using the royal we – I’m talking about my student Jeff Cluever who’s actually doing a lot of the work, as well as a whole host of interns this summer that are are doing the hard work of being out in the field in these hot hot days. But we’re also taking flower samples from the wheat and flower samples from the dry beans when they start flowering and then later this year we’ll, we’ll collect yield of course. But then we’ll also check the beans for damage from western bean cutworms specifically.
So ultimately, kind of our target scenario in this case right now, western bean cutworm is the key pest of dry beans in this region, and so that’s sort of our target pest. As to whether or not we think the system is going to work or not from a bio control standpoint, in July, we’ll have sentinel egg masses that we put out into plots to try to estimate the rate of egg consumption by predators in these systems, to see if the different treatments – whether it’s a relay or whatever – to see what the differences are between these treatments, relative to western cutworm egg mass consumption. And then we would hope that would then translate to reduced injury in the dry beans and increased yield. And so coming back to what we talked about earlier about trade-offs, so our hope would be that we’d have a taller bean so we’d lose less yield and then because of the system that we’ve established, we would have more bio control. So we should see a higher quality bean and then historically, we’ve had to rely on chemical control means uh to manage western cutworm. So it’s a high bar, but um one bar we’ve got with this in terms of a goal post is to see if we could eliminate or significantly reduce insecticide input into the system so we may be able to replace that insecticide cost effectively with wheat seed costs and that wheat seed costs – one would hope within an ideal world – pay for itself with the grain that you collect off of the wheat crop. So sort of the production side of things, that’s kind of how we’re seeing it. We see these replacements and so ultimately, I know that we are anticipating we should see less dry bean yield in the relay system unless we fine tune it further as as the seasons go on but we would hope that we again have a higher quality bean and recover more of that yield and spend less money on on insect pest control.
13:37 E: Well folks, today we’ve talked to Dr. Jeff Bradshaw about his relay cropping system research, what some of those compromises to be made are, and what his research is specifically looking at within entomology.
Come join us next time on Farm Sci-Ed as we go into the science and education behind farming.
Be sure to like this video, subscribe, and follow us on twitter or on our website at farmsci-ed.com
for more science and education behind farming. Have a good one!
Join Emily and Bob as they discuss the Cercospora leaf spot in sugar beets.
00:30 Emily: Hi everyone! Welcome to Farm Sci-Ed. My name is Emily Stine and today I’m interviewing plant pathologist Dr. Bob Harveson, who’s doing some really interesting work on cercospora in sugar beets. So sit back, relax, and let’s go learn.
Bob: Sugar beets are plants that are greatly a result of breeding. It was found that this particular beets – in general, fodder beets and other types of beets – had sucrose in them, which is the same product that is produced by sugar cane.
So it allowed temperate areas to produce sugar, which then enabled everybody to be able to – it made it more available to the general public. Because previously, it had all come out of the tropics – you know from the cane – and so it was exorbitantly expensive. So it’s a crop that they have bred to the general plant that they have now. So there are high, high levels of sucrose within that plant and it’s the same type of product that is by the totally unrelated sugar cane. Which is kind of odd, but that’s I think, an interesting fact.
B: Well they’re grown out here the western part of Nebraska, but then it’s also in Colorado, Wyoming, and there’s a great deal around the Great Lakes, Michigan and then Minnesota. North Dakota is the largest number of acres. So it is grown in various places. It’s grown up in the northwest and same in Idaho as well.
B: Cercospora is a fungus. It’s the generic name for a fungus that causes – it’s an airborne thing. The spores fly through the air. It just causes a foliar disease of sugar beets and other beet related: table beets,
those sorts of things, they’re still susceptible to this.
The other thing that I wanted to point out is that it can be confused with a number of other foliar type diseases that we might see here, but it’s the only one you have to be worried about. It’s the only one that causes economic damage, but it could be confused with alternaria leaf spot or with bacterial leaf spot.
It can be very very devastating, not only to to yield, but also in that it doesn’t sit well in the piles, so it doesn’t process very well. So you just, you just lose a lot of the sucrose because of this infection. Not only in yields, but later on for processing.
2:56 E: What kinds of environmental conditions favor cercospora development in the field?
B: Well it’s – it does have a very specific set of conditions that it needs. It needs a long period of water, duration of at least 11 hours of standing water on the leaves and so forth.
It also needs a [specific] temperature range. If it gets down below 60 degrees Fahrenheit, then then it won’t be a problem. And then if it gets up higher to 95 to 100 then it’s not going to be as much of an issue either. So you need the combination of warm temperatures with a lot of water.
3:31 E: How do sugar beet growers manage cercospora in the field?
B: Well, there’s a number of ways. One of the first things, like I mentioned a while ago, is you need to make sure that it is cercospora that you’re looking at. ‘Cause if it’s one of those other diseases, you’re going to waste your money because they weren’t going to be economically damaging anyway. And then you’re just out the cost of the chemical.
I guess the most effective way, or the most cost effective way, is through genetic resistance. They have done a really good job of doing – of finding resistance – and then incorporating it into new varieties which are agriculturally successful.
Other things you can do: different types of tillage so it it it can – it basically survives in residues, plant residues. So if you can get that buried or if you can get it out of the way, then that’s going to also help you to a great extent. It’s going to remove that source of inoculum. It doesn’t move a great deal, but it can move through wind patterns.
So, what the idea is to not – if you’ve had a field that had a severe amount of disease, then don’t put another crop the next year within a hundred yards of that.
Fungicides are another option that are routinely used and if you combine those with with the resistance then that that’s even better. But the problem with the fungicides is that there’s populations that have built resistance towards these fungicides and so that’s something you always have to keep in mind. And it’s something that we are continually trying new things to see just to look at different chemistries or different products so that we don’t all – we don’t lose products because of the genetic resistance to that. And that’s so, that’s a huge part of that is not to use the same chemistry multiple times in a year.
5:21 E: How do they track these environmental conditions?
B: Well, we – they do have – we do have a predictive system that has been in place since the 1980’s. It was developed by my predecessor Eric Kerr, and then another UNL faculty member. It’s basically an alert system that that tells you the environment. Its advantage is that it tells you whether the temperature and the moisture has been right for infection to occur. So it doesn’t tell you that the pathogen is present, it just says “hey”.
It’s a monitor, you take it and put it in the fields, and then each day you go and take a look at it. And then it gives you a numerical value of 0 to 14, which is a formula and it’s based on a hourly time for for for the temperatures. Then it spits out a number through a formula of 0 to 14 and so you take that number, that’s the the daily value for disease for that particular day. And the idea is that when you get two successive days in a row where the sum of those two daily infection values reach 7 or higher, then that means the previous 48 hours have been conducive for disease to occur. It doesn’t mean the pathogen is there, doesn’t mean disease is there, it just means that it has been conducive for that to happen. So it makes you have to get out and go check and see if there’s any any of those types of things. So when you do see something and it is building up into the upper part of the canopy, then that’s probably a good idea if if that system told you that it’s time to pull the trigger on it, then you need to you need to have – be prepared to do that.
7:11 E: How has this alert system improved over time?
B: Well I don’t know if we’ve improved it, but we’ve been working with Xin. It was his idea to take this system – he’s not changing the system – but he’s made a a device that allows people to access that information remotely and not having to go out into the field to pick it up. So that’s the key to that thing.
Another thing that we are looking at this year for the first time is essentially a spore catcher and so we put that out there with the the monitor for the for the environmental stuff. And so it should tell us: are the spores present of the pathogen? And so you combine that together with the environment, then that would – I think – be a more effective way of determining whether you need to spray or not.
Because again, spraying indiscriminately is not a good idea. There are chemicals that are available that we can use if things come to that situation.
8:10 E: Does the kind of fungicide a producer use matter?
B: What I’ve found in the past, is that the fungicides that you use are not as critical as using them at all. So if if you don’t do it and you have big problems then that’s worse than than using the wrong product I guess. So that is a critical thing. But you don’t want to wait too late, but you also don’t wait too early too. Because that’s not gonna –
most of these fungicides are contact, so they’re not going to get in the plant and last a long time. So this would be considered a short-term solution, and that that’s why it’s so difficult to work with. Its that you’ve got to be cognizant of the fact that “hey the last 48 hours have been conducive for this so I need to get out there and see if any infections have moved up the plant.” Because if you get them on the newer leaves, that’s when you start to see the issues with the yield drop and all that.
9:13 E: Well folks, there you have it. In talking to Bob about sugar beets and cercospora, we learned what sugar beets are, what cercospora is, and what some of the management techniques are, including using fungicides for short-term management.
See you next time on Farm Sci-Ed, where we go into the science and education behind farming. Be sure to subscribe and follow us for more science and education behind farming. Comment below if you have any questions about cercospora in sugar beets and we’ll be sure to answer it in an upcoming episode. Until then, subscribe to our channel, like this video, and be sure to follow us on our social media. Have a good one!
This transcript has been edited slightly for grammar.
[00:19] Welcome to Farm Sci-Ed, the show where we go into the science and education behind farming. Farm Sci-Ed is a behind-the-scenes look at integrated pest management research in the western panhandle of Nebraska.
[00:29] Over the course of the season we’ll explore studies focused on some of the common agricultural pests in our region. This season we have three research projects: a wheat and dry edible bean relay study looking at conservation ecology and biological control (entomology), a series of dry edible bean and palmer amaranth studies looking at plant interference and herbicide options (weed science), and the detection and refinement of a warning system for the sugar beet pathogen Cercospora (plant pathology).
[00:59] Come join us as we explore the research Jeff, Nevin, and Bob are doing in the panhandle of Nebraska and explore the significance of their studies.
[01:01] Subscribe, follow us on social media, and visit our website at farmsci-ed.com for more science and education behind farming.
