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.
