00:00:05] Intro This is a GRDC podcast.

[00:00:13] Shannon Beattie Sclerotinia in lupin is a sporadic disease found across the WA grainbelt. When weather conditions favour disease spread, it can cause significant loss of yield and grain quality. Hi, I'm Shannon Beattie. With GRDC investment, collaborative Research by the Department of Primary Industries and Regional Development, the Centre for Crop and Disease Management, and the Mingenew - Irwin Group has been looking at ways that lupin growers can learn to recognise risky scenarios and employ management strategies to reduce impact of the disease. To find out what the team has discovered, I'm joined on this episode by DPIRD research scientist Ciara Beard.

[00:00:50] Ciara Beard So, sclerotinia is a fungal pathogen that affects broadleaf crops, including lupins.

[00:00:54] Shannon Beattie And how does it differ to sclerotinia in canola?

[00:00:58] Ciara Beard So in our research we found that it predominantly infects the main spike pods, which is where it causes most yield loss, whereas in canola the main effect is the infection of the main stem. So, it means that in lupins the disease needs to be managed differently to the way it is in canola.

[00:01:16] Shannon Beattie I believe we've known about sclerotinia in canola for quite a while, whereas sclerotinia in Lupin is a little bit newer. Do we have a reason for that and why there's not been too much research in this area in WA before?

[00:01:28] Ciara Beard Yeah, so I guess sclerotinia in canola has been researched for the last decade or so, but with the increasing area sown to canola, there's much more risk now of sclerotinia infecting other species like lupins, because the sclerotia intensity in the soil is much greater with the amount of canola being grown. So, it's just that lupins are grown in close rotation with canola, they become higher risk for getting sclerotinia as well.

[00:01:54] Shannon Beattie Before we go into the project, I want to find a little bit more about this disease and how it works. So, I believe there are two types of sclerotinia infection in Lupin. Can you talk to me about those?

[00:02:07] Ciara Beard Sclerotinia sclerotiorum, the pathogen that we're researching this project, can infect in the canopy, which infects the pods, the upper stem and the branches. Whereas the basal or ground level infection infects at ground level on the stem and also can sometimes infect below ground, the roots as well.

[00:02:24] Shannon Beattie And how does the infection process work? How does the plant actually get infected by sclerotinia?

[00:02:31] Ciara Beard The sclerotinia lifecycle is rather complicated and it's heavily dependent on the weather. Our research partners, CCDM, did some work where they found that the fruiting body that spreads the disease around that they require hot weather over summer to be primed to germinate. Then when it rains in autumn and winter, and then once they've germinated, they start spreading ascospores and they infect the petals on the lupin plants. And in lupins, the petals somewhat stay put and infect the pods as they emerge on the plants. And that's where canopy infection comes from. But sometimes the petals obviously can fall as well, a bit like canola, and fall into the canopy and create leaf infection and sometimes stem infection. And then the plants get infected and the sclerotia start forming inside the stems and the pods and then harvested inside the grain sample, which is a really big problem for growers because they have to grade the seed out for delivery. So that's a big difference between canola and lupins as well, in that it's usually the upper part of the canopy that the sclerotia form, then they fall into the soil or they're in the seed and so the cycle just keeps on going. The problem in that paddock, or if you use that seed without cleaning it for the next few years.

[00:03:49] Shannon Beattie What issues does sclerotinia cause for growers? You just mentioned that it can cause a bit of a nightmare to harvest, but what issues are we talking about for growers?

[00:03:57] Ciara Beard The biggest one we're researching is yield loss. So, we find that the pathogen can infect the main spike pods and then the main spike pods get aborted in most cases. And so, there's no yield that comes from the main spike. So that is significant yield loss, so we find eight to 10 per cent yield loss on average in years where the infection occurs. And in the case of basal infection, the whole plant can be taken out because the infection causes stem rot at the base of the plant and then no pods will fill on the plant. So that one can cause almost 100 per cent yield loss if the plant gets basal infection. So, there is also the quality concerns that we mentioned, and that's something that we're researching. But so far, the sclerotia contamination of grain we find is highly variable. And it's actually really hard to quantify and to actually see what management strategies might be effective for reducing it.

[00:04:52] Shannon Beattie Let's go into the project. Can you give us, I guess, just a short summary of what it is you're actually trying to achieve as part of this project or what you're trying to do?

[00:05:00] Ciara Beard We've been looking with our research partners at the infection process, the yield and grain quality impacts, and also the management strategies that growers could employ to combat this disease. So, one of the other things we've been doing is looking at the distribution of the disease across WA. Because until now we haven't really known is it a big problem in lupins and which port zones is it most predominantly a problem in?

[00:05:27] Shannon Beattie Can you talk to me then about the actual trial work that you've been doing? I understand you've been out in the field and doing a bunch of other things. Talk me through what experiments you've been running as part of the trial.

[00:05:37] Ciara Beard In our research, we've been conducting lots of small plot trials, sometimes on growers' properties and some on our research stations. And also, growers have been conducting some work on a large scale, so that's really great because the growers who are impacted by the disease are actually involved in the research. So, some of the things we've been looking at are time of sowing, crop rotation, crop density, things like using wider row spacing and lower seed rate, to see if that reduces the humidity under the canopy and reduces the risk of sclerotinia. And then we've also been comparing Albus lupin and narrowleaf lupin to see if there's a difference in the infection incidence. And also comparing narrowleaf lupin varieties just to see if maybe there are some varieties that don't get has infected as others, so that might be another management strategy growers could use.

[00:06:27] Shannon Beattie Before we get into the findings, I believe you've had some partners in this project. So, can you tell me about the different partners involved and what their roles have been, what they've been looking into?

[00:06:37] Ciara Beard One of the great things about this project has been the collaboration, and within DPIRD we have teams across the Wheatbelt in Geraldton, Northam, and Albany. And so, we're doing lots of field research there. And then at Mingenew we have the Mingenew - Irwin Group who are doing field scale grower trials, and we also have a few growers in other places who are also researching different strategies they'd like to try. Our research partners, Centre for Crop and Disease Management at Curtin Uni, they've been predominantly looking at the infection process in the lab and also in the glasshouse, doing some pot experiments. And they've done some really valuable work, working out how to actually cause basal infection in plants, in pots, so that we can work on strategies to see if we can reduce the yield loss and look into how the infection actually occurs.

[00:07:27] Shannon Beattie Let's go into some of the results and some of the findings that you've made so far. Maybe we start with what you've learned about the different factors that can influence the severity of the disease in a crop.

[00:07:40] Ciara Beard One of the most integral parts, I guess, of the project that we've been working on is how growers can determine whether they're at high risk in a given season, in a given paddock for the disease. Because it is really sporadic and it's really hard to predict and challenging to manage. So, the different risk factors that we have investigated include the previous history of the disease. So, you're much more likely to get sclerotinia in lupins if you are growing in a paddock that's previously had sclerotinia in canola within the last five years. If you've got a higher plant density and a really early canopy cover in your lupin crop and really good yield potential, that kind of bulky crop stays wet for longer and the infection just really gets exacerbated underneath. So that's a high risk, as well as heavy soil type. So, crops that are on a heavy soil type and in a low-lying part of the paddock, such as like a riverbank or bottom of a hill or something like that, they're much more likely to get severe infection and require management.

[00:08:39] Shannon Beattie What have we learned about the way weather impacts the disease and how it spreads around the paddock?

[00:08:45] Ciara Beard That's a really good question because lupin sclerotinia is affected really significantly by weather, even more so than canola sclerotinia. And we find that specific weather at each paddock is actually a really big factor in determining whether you're going to get significant disease and whether you're going to get a yield response. So, we have weather logs at all our trial sites, and what we've found is that the seasons are really wet, that have ongoing moisture throughout most of the growing season, particularly a wet spring, are more likely to get significant levels of sclerotinia in lupins and more likely to get a yield response.

[00:09:22] Shannon Beattie Let's go through that a little bit more and it takes us on to the fungicide side of things. Why is it that a wet spring is actually, I guess, sort of good conditions to have it in because you get a better yield response by spraying a fungicide in a wet spring?

[00:09:36] Ciara Beard Yeah, so it's kind of a combination of a few things. So, the weather starts warming up in spring, and so that's when we usually see the sclerotinia really start to ramp up. So, it prefers temperatures of 16 to 25 degrees. So usually, winter's a bit cooler and nice and wet, but the disease doesn't take off until we get a few warm, sunny days, and the humidity develops under the crop. And then the infection is obviously encouraged by more and more rain and the bulkier crops. Usually, we find that if you have a wet spring, the crops get really bulky and they're just more likely to have that humidity that's required for the disease to keep going and the yield potential to make it worthwhile. Also, if we have a wet spring, we've found in our research that we can sometimes get up to a 25 per cent or even 100 per cent yield response if there are other diseases there. So, for example, in Albus lupin, anthracnose is a really big issue and can cause severe yield loss. So if you are managing sclerotinia in Albus lupin, you're much more likely to get a yield response because you're also be managing for anthracnose, which the same fungicides are registered for.

[00:10:45] Shannon Beattie Staying on fungicides for a little bit. What have we learned about the best time and place of the plant to spray and how it differs from the canopy infection to the basal or the ground infection?

[00:10:57] Ciara Beard So lupin sclerotinia as I said, predominantly causes yield loss by infecting the main spike pods. So that means that the best time to apply the foliar fungicide is as those main spike pods are forming. So that's when the mine spike is finishing flowering and at early pod emergence on the main spike. So, in our research, we found that that's the best time to protect the emerging pods and more likely to get a yield response from that. Unfortunately, though, that timing doesn't usually reduce basal infection, which is like at ground level or below ground level. So unfortunately, at this stage we don't recommend application at that time for controlling basal infection. We're still doing research in that area. In some cases, we do get a response, but in most cases we don't, so it's really inconsistent.

[00:11:47] Shannon Beattie And I believe growers also need to sort of be able to tell the future a little bit and be able to spray for this disease before they actually start seeing symptoms. How are they supposed to do that?

[00:12:00] Ciara Beard That's really, really challenging. And so, in the case of sclerotinia in canola, which is the same that you need to apply the foliar fungicide before you see the symptoms to be most effective. We have come up with the sclerotinia CM app, which plant pathologists across the country contributed to. And so, at this stage for lupins, we're on the way hopefully to developing a decision support tool. But at this stage we have a lupin sclerotinia disease risk assessment guide, and that's really valuable for growers to get hold of. It's on the GRDC website and it just helps you to understand the disease drivers and help you prioritise which paddocks and which growing seasons that you might need to manage the disease. So, it just goes through all those risks that I mentioned earlier and also some of the considerations of when it would be worth putting a fungicide on.

[00:12:48] Shannon Beattie Moving away from fungicides, as part of this project, as you mentioned, you've been looking at row spacing and variety. What have you learned about non-chemical management options that growers could be using? Do you have any tips that you could give in that area?

[00:13:01] Ciara Beard So with our time of sowing trials, we've mostly had those in the Geraldton port zone, and we've found pretty much consistently that the early time of sowing usually gets the most disease. And I guess that depends on when the rain falls and that kind of thing. And the key driver for infection is obviously when the apothecia are out and spreading the infection to the petals, you obviously need the crop to be flowering at the time the apothecia are present. So, there's a few factors that obviously have to line up. And this is where ultimately a decision support tool will be invaluable because it's very complicated process. But the key seems to be that if you have an early crop go in and you're having regular rain and you have a good canopy cover, then the crop is going to be in the ground obviously for much longer and be at higher risk than a later sown crop. So that's what we're finding so far with time of sowing.

[00:13:53] Shannon Beattie Yeah, so that's time of sowing. How about row spacing? What have we learned about that and how growers can use that to their advantage?

[00:14:02] Ciara Beard We're really interested to know if reducing crop density would reduce the risk of sclerotinia in lupin, because in theory, the wider row spacing and a lower seed rate would allow more airflow in a crop. And so less humidity should mean there's less likely a chance of sclerotinia to develop to significant levels. So, we've had several trials looking into this over the years and unfortunately, most of those years we didn't get enough rain at the right time to get disease. So, fingers crossed this year's trial will help us answer that question. But at this stage, through all the years that we've been doing it, we definitely can see that our humidity loggers under the canopy are showing there's much higher humidity where you have narrow row spacing and high seed rate. So, the theory is that it really does seem promising that that could be an option for growers going forward.

[00:14:54] Shannon Beattie Has any research been done onto those fruiting bodies that you mentioned that are kind of floating around the place and they're what's causing this vicious life cycle of the disease to keep going? Is there any way of getting rid of those?

[00:15:06] Ciara Beard Yeah, so that's a good challenge that we've been trying to address for a few years now. And in the past, we've tried grinding them up with a coffee grinder to try and stimulate the weed seed destructor. And, you know, they were turned into powder and they still germinated, which is quite terrifying. But there were obviously not as many germinated, so it did affect them a bit, but they were still able to germinate. So, what we've been doing lately is looking at applying fungicide to the actual sclerotia to see if they actually come in contact with foliar fungicide, would that reduce their germination? And unfortunately, they're very hardy little buggers, they're still germinating. So myceliogenically to produce the fungal hyphae that could cause basal infection, and also carpogenically to form the apothecia, the mushrooms, they're still doing both. So, some of them are possibly reducing a bit, but the fact that all of them are still germinating is really quite worrying. And the latest thing we've tried is waiting until the apothecia form, that's the little mushroom, and then spraying those with fungicide because we thought maybe we could get inside the rind that way. But unfortunately, they still seem to be very rugged, and they haven't been a significant reduction in their persistence. So, at this point we don't recommend any management strategies to target sclerotia or apothecia because at this point there hasn't been a fruitful exercise, and growers would be wasting their time and money if they were pursuing that. But we're keeping researching because hopefully there's something that will kill them.

[00:16:37] Shannon Beattie So watch this space on that one, hopefully we have some more news in the future about a solution to that problem. To finish up with, I'm interested in why research that's been done on sclerotinia overseas and interstate isn't really relevant in WA and why it's been necessary for DPIRD to do its own project in this space with this GRDC investment.

[00:16:59] Ciara Beard So sclerotinia is very common in broadleaf crops around the world. And what we've found is that even within Australia, how the pathogen behaves is really quite different. So, in New South Wales, they have a research project about sclerotinia in pulses, but what they're finding is a bit different to what we're finding. So, in Western Australia, as I said, one of our research partners, CCDM, have done work looking at how the sclerotia survive over summer, and in fact the hot weather over WA's summer actually favours them and primes them. Whereas over in Europe and Canada they need a chilling requirement. So, the sclerotia have obviously adapted to the local conditions, and that's why we need to do local research and why this project was so valuable, and growers were really keen for us to do some work here in Western Australia.

[00:17:48] Shannon Beattie Ciara, thank you very much for joining me on the podcast.

[00:17:50] Ciara Beard Thank you very much, Shannon.

[00:17:58] Shannon Beattie That was Ciara Beard from DPIRD talking about managing sclerotinia in lupin in WA. For more information on this topic can also be found in the description box of this podcast online at GRDC.com.au. I'm Shannon Beattie and this has been a GRDC podcast. Thanks for listening.