Hi all, it's Justine McNally here from Local Land Services in the North West of New South Wales. I'm the District Vet based in Moree and I just want to welcome everyone to this webinar, and I hope you all get something out of it in relation to fly strike. We've been really fortunate to get Narelle Sales from New South Wales DPI to present, and Narelle's got three decades of experience around both fly strike and lice control, so we're really fortunate to have Narelle talking to us today.
What we're going to do soon is a very, very quick poll, and it was just so Narelle and myself can see what products people have been using over the last 12 months around fly and lice control, because there's a little bit of crossover with the chemicals there. Some of you would have got my email yesterday in relation to that, just to give you a little bit of a heads up to go and have a look on the labels of the containers you've got at home. Hopefully you've got those written down, because in the poll questions I've done it so that they've got their chemical ingredient name, and I've got just an example next to them of one of the generic brand names. But yeah, it'd be really helpful for us to get a little grip on what people are using.
Okay, so hopefully everyone can hear me. What we might do—we've got quite a few people on now—we might just head to the poll questions. They'll come up on your screen and just tap on the answer that applies to you. Okay, so I'll give you a little bit of time to answer, but we're just going to go with the first one, and that is: what is the active ingredient of the lice control program you'd use?
So if people want to start trying to answer that, hopefully I've done the right thing. Okay, that's great, thanks guys. So just out of interest, it looks like most people have either used that imidacloprid or spinosad, and there's some that have used ivermectin, a little bit of the others.
Okay, so what did you use for 2020 fly control? So I'll just launch that. Okay, I'll close that out. So most people here look to be using something like Clik, the dicyclanil, and then a smattering between the other things.
Okay, the third question is: what have you used as your dressing treatment? Okay, looks like most people have got their votes in. So on that one, it looks like most people are using spinosad, and then the breakdown otherwise is between OPs and ivermectin.
Then the next question is: what were you thinking of using for this season's preventative treatment? So looking at this, we've got about two-thirds of people are thinking of using dicyclanil, and then around that 20 percent mark for imidacloprid and cyromazine. So there's a few for the others, but that's good, thanks.
Okay, and then the very last question is: what were you thinking of using for this season's dressing treatment? Okay, it looks like most people are going to be using—that sort of two-thirds will be using—spinosad, and then the other 20 percent OPs or ivermectin. So that's great.
Okay, thank you everyone for doing that. I'll just give you a little bit of a hand as we move through the presentation, because you'll be able to sort of follow what Narelle's talking about and just alerts you to the chemicals that you're using.
Okay, just moving on now. Just before Narelle starts, I'd just like to do Acknowledgement of Country. So I've got this nice artwork that I was shared by a work colleague who's helping me with this webinar, Leone. But I'd just like to acknowledge the Traditional Custodians of the land where I am today, the Kamilaroi people, and their Elders past, present and emerging.
Okay, I think with no further ado, we might just move on to Narelle's presentation. So I'll just share the screen with Narelle. Just bear with me for five seconds.
Flystrike Overview
So hopefully, there we go. Narelle, it's over to you.
Well, thank you very much Justine, and thank you for inviting me to give this talk today. As Justine said, I work at the Elizabeth Macarthur Agricultural Institute, which is approximately 1600 hectares. We have laboratory facilities, we can do pen trials, pasture trials, and we even have high biosecurity facilities on site.
I've worked on ectoparasites of livestock for more than 30 years—about 30 years at the department. So the information I'm going to provide today, the data that I'm going to provide, can be found in this final report that's on the AWI website, which is listed here. The advice comes from a working party that was put together by AWI on the back of the findings of this project.
So as you all know, I'll just go through some of the basic stuff to start with. I don't need to show anybody a picture of fly strike. There on the left, these are pretty much fully grown maggots. These are what they look like when they're all cleaned up. This dark bit here you can see is their crop—that's full—so they've been actively feeding. This picture here is of a male fly. Lucilia cuprina initiates more than 90 percent of strike in Australia, and that's why we call it the primary sheep blowfly.
There's really good general information in a New South Wales DPI Primefact Number 485, which you can access on the website. There are what we call secondary flies, which come in once that strike is initiated. These big brown ones—so here's the normal one with Lucilia cuprina that'll initiate it—and these big brown ones, you know, we call them brown blowflies or some people call them brown bombers. Their maggots are a bit larger and look a slightly different colour. Then this one here on the far right-hand side is Chrysomya rufifacies, and the larvae for that are these ones that we call spiky or hairy maggots.
Usually these are the last sort of invaders, and when you see them, you know that the strike's been there for a while. These are the ones that really have that capacity to actually end up causing death—septicaemia and death in the sheep. So this is what you probably are all pretty familiar with.
I'd just like to point out that there's fly strike you see and fly strike you don't see. So we call the fly strike you don't see "covert strike", and there was a great study done back in 1984 by Wardhaugh and Dalwitz, and they found that strike can continue for up to two months without being able to be detected. They also found that, depending on the sheep type and the season, that covert strike that you can't see may be five to fourteen times more prevalent than the overt strike—the strike that you can actually pick up and see.
This is a life cycle of a fly—of the sheep blowfly—which you're all familiar with, but we'll just go through it quickly. Female flies lay eggs on the fleece. These hatch out into what we call larvae or maggots. When they hatch out, they're what we call first instar maggots. They're exactly like a snake and they need to shed their skin to be able to grow to the next stage. So they actually shed their skin twice. They go first instar, second instar, third instar, growing the whole time. So that maggot stage occurs on the sheep.
When those maggots are fully fed, they will enter what we call a wandering phase, where they drop from the sheep and they'll burrow into the soil. Now, if the soil is less than 15 degrees, they'll go into this stage here, which is known as a pre-pupa, and they'll stay in that stage until the soil warms up.
This is why you get a fly wave at the beginning of the season—because the soil warms up—and these will continue to progress through to pupae and then the flies emerge virtually as a synchronised population. If the soil is above 15 degrees, this development goes through normally. When they sort of go into a soup inside the pupae and then they turn into a fly, when the fly emerges they burrow, they come back out of the soil and they look like this, and they have to blow their wings up and puff themselves up and then they harden. Then they're able to fly once they've blown out their wings and hardened up.
Their main aim is to find a mate and mate, and then of course off we go around again when the female lays her eggs. You can see this is a time scale, and that is temperature dependent. It can be faster under hotter temperatures and slower under cooler temperatures, and again that information is in that Primefact 485 that I mentioned earlier.
So the co-funded project between AWI and DPI was conducted from November 2017 through to June 2020, and these coloured areas are the areas that we received strains from. The number in the little grey circle, if you can see that, that's the number of samples that we received from producers from that area. Bear in mind most of New South Wales—I think all of New South Wales—was under drought, and there was a fair bit of drought across Australia. When I say samples, producers submitted samples—they actually went out, collected maggots off sheep, put them in containers and sent them in to us.
Insecticide Resistance Definition
So I'd like to talk about insecticide resistance, but first of all I'd like to give you a definition of what I mean when we're talking about insecticide resistance. This is an internationally accepted definition, and it's a really good practical definition. The few points to notice: it's a heritable change in the insect, and that heritable change means the genetics of the insect have been changed. It talks about the sensitivity of the population, and that if there's a change, that will be manifested as a repeated failure of a product.
I suppose the most important thing here is the expected level of control that you would be looking for from that product. In Australia, we have the process that goes through APVMA, and there's a protection period that's normally stated on the label, and often that will read something like "up to 14 weeks" or thereabouts. So: a genetic change, repeated failure of a product at the expected level when it's been used according to label recommendations.
Resistance Levels
There are two sides to resistance, or two ways of looking at resistance. One is the resistance level—that's how high is that resistance, how much insecticide do you need to put on to kill the maggot. The measure that we use so we can compare all of the strains is known as the LC50, and that's the concentration that's required to kill 50% of that population. So it's sort of the benchmark for all strains, and then we can compare the strains when we look at this single index.
When we've calculated that for a field strain, we can determine a resistance factor, and we divide that LC50 of the field strain by the LC50 of a strain that we have here in the laboratory that is completely naïve to insecticide and we know it's susceptible to everything. So this is our baseline, if you will, and that allows us to calculate a resistance factor.
The other side of resistance is resistance frequency, and that refers to how many maggots in that strike or how many flies on the wing are actually resistant in that population. How we determine that in the laboratory is we know what is known as a susceptible discriminating concentration. So most chemicals, before they come out on the market, we have access to them and we're able to determine a concentration at which we know all susceptible maggots or flies will be killed. We can then use that concentration when we get a field strain in—we can screen that field strain with that concentration and we can get a percentage of the population that we know is resistant.
Why Do We Even Bother Laboratory Testing?
We do that for some very good reasons. There are a whole heap of factors that come into play with that fly when she's looking to lay eggs on a sheep. Before she'll even get to that sheep, there's a whole heap of environmental factors, and then there's a whole heap of sheep factors and climatic factors that may mean that she either doesn't get to lay or that when she does lay those eggs don't hatch. So what we do in the laboratory is we keep the temperature and humidity constant, and we rule out all of these factors that have a nil next to them.
The most important one, I suppose, really is exposure to other chemicals—so we are only looking at the effect of a single chemical. In the laboratory we give them unlimited food and water, so we know that's not a limiting thing, and we're able to dose with highly precise concentrations of insecticide, and we can do that with high repetition so that it's valid to be able to compare the results for different strains.
Insecticide Resistance Table
This is a table of insecticides that are no longer registered for prevention. Resistance is like a serial Danish—layer upon layer—if you remember the old ad. So once you stop using an insecticide, often that resistance remains embedded in the genetics if other things have occurred, and that becomes part of the backdrop of what you're looking at. You'll see from this list that OPs are no longer registered for fly prevention. This column is the year that these products were introduced; this is the year that resistance was developed. In the brackets you'll see how long it roughly took for that resistance to develop, and in the far right-hand column is whether or not we included them in the 2018 to 2020 study.
We did include the organophosphates, and we included the benzoyl phenylureas, which are an IGR—you may remember diflubenzuron and triflumuron—and we included that for historical reasons.
This is a list of currently registered products for fly strike prevention. This is the insecticide group—that's the name of the group—and when we get later to rotation, this is what we're asking you to rotate between. These are the insecticide names, which is what you would need to look at as your active ingredient on products. Here are some example products if you're not familiar with these active ingredient names. Again, the year that they were introduced and the year that resistance was detected, and in brackets the number of years that it took for that resistance to develop.
So you can see here cyromazine resistance—it was 32 years before resistance was verified in the field. Again, dicyclanil resistance was found in 2011 as well in a few populations, but it was thought to be at low levels. The big news was really cyromazine resistance. When we started this survey at the very end of 2017, it became pretty clear pretty quickly that things had changed. So I've got 2017 here because it was very obvious that things had changed fairly dramatically since 2011. The final column is whether or not the chemicals were included in our study. You'll see here we didn't include cypermethrin, which is a synthetic. You might know it as Vanquish. It works in a very different way—they paralyse the ovipositor of the fly and she lays scattered eggs rather than laying nice clumps, and the eggs, if she lays them at all, will desiccate and not hatch.
Resistance Testing
So I'm looking at the resistance testing we did for cyromazine and dicyclanil. Because they are an IGR, we had to do a different type of test to the OPs and spinosad and ivermectin and imidacloprid. In the test for cyromazine and dicyclanil, we have to incorporate the insecticide into the food, and we put newly emerged first-instar larvae on there. So as soon as they hatch out of the eggs, we count them on, and then we let them go through their entire development phase on that media. If they feed fully, they come off, they'll form pupae, and then they'll hatch out as adults. So when I say that there were survivors against cyromazine or dicyclanil, I'm actually talking about adult flies that have hatched out—not that they've killed maggots.
We do that because these are what will be the next generation to produce strike on your sheep.
Survey Results
When we did the survey across Australia, we had 21 samples come in from Western Australia, 12 from South Australia. We did receive three from Tasmania, but unfortunately only one was viable for testing. Victoria: 11. And New South Wales: 55. We had a total of 100.
You'll see the colours: the green is for populations that were susceptible to dicyclanil and cyromazine—so no adult flies emerged from the assays in these populations. The yellow are populations that were just resistant to cyromazine, and the red are populations that were resistant to both dicyclanil and cyromazine.
So you can see here in Western Australia, almost 50% of what we received was resistant only to cyromazine, 28% was resistant to both, and 24% were susceptible. South Australia—slightly different again. The one strain we tested in Tasmania was susceptible. And in Victoria, one strain was susceptible to dicyclanil and cyromazine, one strain was only cyromazine resistant, and the rest were resistant to both chemicals. In New South Wales, 100% were resistant to both chemicals.
In the last year, in 2021, we've actually tested another 23 strains from New South Wales, and this story hasn't changed in that time.
Pasture-Based Study
So what's important to producers is that protection period that I was talking about earlier. They want to know: if they put it on their sheep, how many weeks' protection will they gain from the use of a product? And they really want to know: if there is resistance, how will that affect that protection period?
So we did a field—a pasture-based study—and we used what's known as the implant technique. Now, this implant technique takes those newly emerged first-instar larvae, puts them onto a wet cotton dental wick (which is the same as what the dentist puts in your mouth when you visit), and on the sheep that have been pre-treated in this trial—they were treated six weeks off shears—we part the wool, scarify the area slightly, spray with the spray bottle to slightly moisten, and then we put this dental wick with approximately 200 larvae over the top of that area. Then what you see in the red circle there is a bulldog clip, which is used to hold it into place.
Twenty-four, forty-eight, and seventy-two hours later, we checked on each of those implants, and here you can see well-advanced feeding third instars—a well-advanced strike on one of the sheep. We sat and picked all the maggots off the sheep that we could find, took them back to the laboratory to see if they would pupate and then to see if the adult flies hatched out. So when I say that a strike was positive, I'm actually saying that adult flies emerged from the maggots that we removed from the sheep at 72 hours.
What I should say is that down the midline of the sheep, we implanted on one side with a strain that was resistant to dicyclanil, and on the other side we implanted with a strain that was susceptible to dicyclanil.
Study Results
So when we did that, these are the results for dicyclanil spray-on-based products. All of these products were bought across the counter, so it's exactly the same as what a producer would use. This is the low-dose one that claims up to 11 weeks' protection. The red column here is the resistant strain; the blue column is the susceptible strain. Along the bottom axis is the number of weeks post-treatment. Again, we staggered the shearing of all of these groups, and then they were all treated six weeks off shears so that these implants would line up, and we adjusted the challenge interval—we challenged every two weeks, but we adjusted when we started, when we first challenged, in line with what the recommended protection period is.
So for the low-dose dicyclanil, we challenged three weeks post-treatment, and you can see with the resistant strain, six out of six sheep were positive. We set a cut-off at three out of six sheep to declare the end of the implants for that strain, or a cut-off for what we classified in this trial as a failure. As you'll see here, for this low-dose dicyclanil product, the susceptible strain did reach 11 weeks—we didn't have that three-out-of-six positive sheep reached until 13 weeks post-treatment. But at three weeks, we had six out of six, and this was backed up at five weeks post-treatment to confirm this first finding.
This is the normal-dose dicyclanil spray-on product that we say normally gets up to 18 to 24 weeks' protection. The first challenge was at four weeks post-treatment, and you can see the very first challenge we got three out of the six sheep were positive, so they met that cut-off. This was confirmed at six weeks post-treatment, where we got five out of six sheep positive. For the susceptible strain, you can see that we actually didn't reach the cut-off of three out of six sheep, so the 24 weeks' protection was obtained against the susceptible strain.
For the higher-dose spray-on product, which gives up to 29 weeks, we challenged for the first time seven weeks post-treatment, and you can see we only got two out of six sheep, so we hadn't reached that cut-off. At nine weeks post-treatment, we actually ended up with six out of six sheep, and this was confirmed the following at 11 weeks post-treatment, again with six out of six sheep positive. Again, the susceptible strain actually met and achieved the protection period as claimed on the label.
Hand-Jetted Results
In that trial, we also hand-jetted with an ivermectin-based product, which claims up to 12 weeks' protection. We challenged at four weeks for the first time, but you'll see here it's not until eight weeks that the resistant strain goes above that cut-off, and that was confirmed at 10 weeks. The susceptible strain, once again, achieved the protection period that was claimed.
You might wonder why this product only achieved eight weeks when there's a claim of 12 weeks. If you read the label on these products, it will state that you will receive up to 12 weeks' protection for low to moderate fly strike challenge. Because we've removed a lot of the factors around that female getting to lay eggs—because we've put first-instar larvae on those sheep—it's basically: is there enough chemical on that sheep to kill those, or to kill or stop, in the case of dicyclanil and cyromazine, the development of adults? So we would classify this as not low to medium challenge, so that's why we only got eight weeks' protection.
We also hand-jetted with cyromazine, which claims up to 14 weeks, and as you'll see we started challenge three weeks post-treatment, but it wasn't until seven weeks post-treatment that the resistant strain got six out of six sheep positive. Once again, we got the claimed protection period against the susceptible strain.
This final group here are the untreated control sheep. This trial ran from August through to the middle of April, and in the middle of summer—in about here—I was sitting picking maggots off sheep and it was 45 degrees. There are environmental tolerances even for maggots, and we run untreated controls to make sure that there's no outside influences that would be reducing the performance of the maggots or coming into play. It's also a test of my implant technique, and as you can see for both the susceptible and the resistant strain, for each implant opportunity we got six out of six positive sheep.
So where does that leave us with resistance, with the information that I've already given you about resistance? We'll go through again the products that are registered for prevention and treatment of existing strikes. Organophosphates—as I said—they're registered as dressings, they're not registered as preventatives. I've also got listed here the application technique, so you can see that some are spray-on but others are available for jetting or dipping in this column. This column here tells you whether or not that group of insecticides is used for lice, and as you can see the OPs—temephos—is still registered for lice, and these bottom four are registered for lice. The final column is whether or not there is known resistance at this time against that group of insecticides.
Chemical Rotation
So I've put this together in line with the recommendation of that AWI-formed working group that recommends chemical rotation. If we start with lice treatment, the recommendation is that you pick one group of insecticides for lice treatments, and so these are what are available for lice treatments. I've coloured them different colours so that when you get down here to strike or wound dressing, you can buy colour. Ivermectin appears here for lice treatments, it appears here as a strike or wound dressing, and it also appears down here as a preventative treatment.
So if we want to pick one for a lice treatment—say for example we picked ivermectin just for the sake of an example—when we get down here to a strike or wound dressing, we want to pick a different group, and we see, oh well, ivermectin's already in that group but I've used that for lice treatment. One of the things we did do in our study was look at the highly resistant strain of blowflies that was highly dicyclanil resistant, and we tested them with the registered dressings. What we found was that the two best performers were the Extinosad aerosol and the old fly strike powder. I think the fly strike powder works so well because it actually sticks to the maggots.
So say for example we picked the spinosad aerosol treatment here—that knocks it out here. So we've got rid of ivermectin, we've got rid of spinosad, and that leaves us these chemicals for a preventative. The alpha-cypermethrin is the one that I spoke about which paralyzes the ovipositor of the female fly, so it works in a very different way. You may not be familiar with that, and I'm not sure how popular that is, but you need to select a third group there.
There's another recommendation that if you treat twice in a season—or twice in a year even—depending on when your fly season is, whether you have two fly seasons or only one bad one a year, that you rotate to another group again. So what makes it pretty clear is that if you're going to rotate between groups, you're going to have to use some sort of wet formulation, and what you need to consider before you start down this path is: do you even have the equipment to be able to do this? I know a lot of people have filled in their old-fashioned plunge dips because they weren't long enough according to the recommendations. There are new spray races and things that are out there available, but if you're going to follow this, you need to have the correct equipment to be able to apply those wet products.
The other thing for resistance management that's a good thing to do is to try and reduce your reliance on insecticides. A lot of producers have spent a lot of time, money and effort into breeding sheep that are less susceptible to fly strike. I've got the word there "resistant" and it's probably not a good word to use when I'm talking about insecticide resistance, but you know all of those things—plainer body, cleaner breech—everything that you'd know more about than what I do really. And to shear and crutch at times to take advantage of the six weeks' protection that both of these operations give you—use that to your advantage wherever you can.
There's been a lot of work that's proved that if you dock the tails of your lambs to the correct length, that it maintains a cleaner breech, and a cleaner breech equals less fly strike. And again, clean a breech by managing scouring with effective and strategic drenching, and breech modification may be required if you haven't got down the path far enough with your breeding just yet. So there are many methods of breech modification, and it's still a valid thing. If you do breech modification, always make sure that those animals are protected—that you're not just putting them out in the middle of a fly strike season where that wound is going to get struck.
So the overall message for reducing reliance on insecticide is to drench, crutch and shear strategically if you're going to use part of this plan. Crutching and shearing—and I know that's easier to say than it probably is to do—but some examples of how you might use that six weeks' protection from crutching or shearing is: if you were to shear or crutch at the beginning of the fly season, then you might only need to have a shorter-acting insecticide applied at the end for the second half of the fly strike season. If you crutched, for example, in the middle of a fly season, you might be able to use two short-actings either side of that.
Crutching and shearing can also be used to reduce what we call selection pressure that a chemical does when it's on the fleece. So when you've applied that chemical to the sheep, the effective concentration may no longer be there, but as long as that insecticide is still in the environment, it's still capable of selecting for resistance on the sheep. So if you shear that wool off—as long as it's inside the wool harvesting period—you're taking that out of the system.
So it's a bit like a tail-cutter drench really, and if you're going to do any of these, always observe the wool harvesting interval that's listed on the products. Often, depending on where you are and what the climate in your area is like and what the prevailing weather conditions are, if your sheep are in short wool you may actually eliminate any need for an autumn treatment—you might get through that autumn period without it.
One of the important things to know is how long the risk period is. Can you use two shorter-acting treatments, or do you need to have a longer-acting chemical? And is there resistance on your property or in your area? If there is resistance, you need to be aware that it doesn't mean that the chemical won't work—it just means that the protection period you get may be less than the label claim, and that you need to be looking at your animals more frequently. You might need to do multiple treatments rather than just a single treatment.
One that's important for everybody to know—and most producers know this, but it's a good thing to double-check—is: when is the highest risk period of fly strike on your property, and how long does that last for? So there's this really great tool on FlyBoss.
Flystrike Tool
It's been developed by Brian Horton at the University of Tasmania, and Brian's spent years doing this type of modelling. You can read there that this pulls on 30 years' worth of data to develop this model. This is the new version that is downloadable, and the trick you need to know is when you click on it you need to go to your downloads to find the file and put it into the folder that you've created. So this is new for those of you who haven't used it before. I'll quickly run through it.
Property Tab
It has a property tab where you can select exactly where your property is, and this gives you the longitude, the latitude, and the file to download into your folder. You can actually select the type of sheep that you're concerned about, or you may be concerned about all of them.
Wool Tab
There's a wool tab that allows you to compare two management strategies, and in those you can input the dates of a single shearing or if you're shearing twice in a year. A lot of producers that I've spoken to over the last two or three years—some of them have moved to shearing six-monthly because it suits their system and it's economically viable. Or you can put in one crutching or two crutchings, and other producers have moved to two crutchings because that's what works for their system. There's a tab down the bottom where you can select un-muled or muled.
Chemicals Tab
The next tab is the chemicals tab, and as you can see here you can select no treatment, or you can press on the drop-down and select a treatment. Then these tabs come up, and on this tab you can select whether you're concerned with body strike, breech strike, or body and breech strike. Then this "Optimized Dates" comes up, and it can actually optimize—I’ve put in two treatments here—and it can optimize the dates of the treatment for your property.
A really cool thing that comes up is an error message. So if I've gone at the front and told them when I want to shear or when I want to crutch, and then I've put in a treatment and it's going to clash, it tells you that you must allow the length of time between shearing and treatment. You can also go directly with this button to FlyBoss to check on products.
Breech and Fleece Rot Scores
The next tab is also new, and this is a great thing. This is where you can enter your breech and fleece rot scores—all of those things that you're now 100% familiar with: breech wrinkle, breech cover, dag score—and you can select whether they're muled or un-muled. What you end up with is a graph like this for every month of the year and the risk of fly strike on your property.
The line across the bottom here that's just flat is other fly strikes—so that's poll and pizzle. The green one here is actually body strike, the purple one is breech strike, and then the thick brown one is all combined.
Online Flystrike Tool
What I'm going to quickly run through is the online FlyBoss tool, which is a bit more basic than that one that I showed you, and I'll quickly go through it and show you how to use it. It pulls data from the closest weather station, and for the coordinates that I was given, Goondiwindi Airport is the closest—so it's somewhere there near the border. You can select whether they're muled or un-muled, put your shearing dates in, put when you do your first crutching, and select your chemical treatments—first or second crutching, first or second chemical treatment.
Shearing Dates
What I'd like to show you was this property—they actually shear in mid-June and then they crutch in mid-March. So if I only put in the shearing and crutching dates and then I look at something with a high breech score—so no and low, so clean breech versus non-clean breech—you can see the difference in the risk, especially given that this isn't really to scale because this blue here is actually that blue and the green there. So your risk for breech strike is pretty high.
Clean Breech
If we add a treatment in early October to that same scenario, you can see that that whole area has totally disappeared, and our main risk area becomes February through to March. This is again with not a clean breech. This is a clean breech, and on the left is something that's not really a clean breech. You can see with a clean breech that risk of breech strike is reduced even further. And then if I was to add a treatment in the first week of February that gave, say, up to 12 weeks' protection, you can see that the risk is virtually removed—and high breech score or clean breech, it sort of makes it irrelevant.
I think last year there were unseasonable rains because this producer had treated in April, and from the modelling of this, the treatment in April was because of unseasonably late rains. Through this model, when I put it through, that treatment in April—based on this 30-year average data—would have afforded no protection because according to the model there was no risk at that time.
Best Practice
Again, you need to know: are you experiencing unseasonal conditions for your area? I'd just like to wind up with what is, from the strategy and from the data that I've presented today, what's been sort of best practice.
The first really important point is to look at your product and know what the active ingredient is, and then know what insecticide group that belongs to, so that when you rotate you are rotating between groups. Remember: cyromazine and dicyclanil all belong to the same group—even though they're slightly different—they are both IGRs. Yep. So rotate your insecticide groups if it's practicable. Try and minimise the number of treatments by having a look if you can play around at all—if you have any leeway at all—to change crutching dates or, if you're developing a longer-term plan where you do intend to change crutching or shearing dates, you can muck around with that model and see when it's most effective for your actual enterprise. And again, rotate to a different group.
Always consider the treatments used for both lice—if you remember back to that sort of flow diagram, that was step number one—and also for worms. There are some chemicals that are also registered and are present in drenches—I suppose I'm thinking of the MLs with that. Apply the insecticide carefully and strictly according to the label. In resistance terms, it is as important not to overdose as it is to underdose, and a lot of people don't realise that—they may just continue to put on more and more and more of the insecticide.
You need to be monitoring fly strike frequently. If you think back to that slide where I showed the difference between the covert strike and the overt strike, there may be a lot more going on that you haven't yet seen, and it's recommended that you do that every second day in the peak fly strike season.
When you're cleaning up an existing strike, it's incredibly important to kill the maggots that come off that strike. You can stomp on them if you're on cement if you want to, but the best thing is to gather them up with a dustpan and broom, tie them in a plastic bag and stick them out in the sun. They're just like you and I—they need to breathe oxygen, and they can be overheated and die of overheating the same as we can—because these maggots become the flies that will be striking your sheep in the next few weeks.
And overall, reduce the reliance on insecticide if you can, because that will slow down the development of resistance.
I'd just like to acknowledge AWI for the co-funding for this project with New South Wales DPI, the great job that Brian Horton has done and has always done on the tools that are found on FlyBoss, and the AWI Sheep Blowfly Resistance Management Strategy Working Group that I mentioned—they're the people who sat on that to come up with this rotation strategy.
Disclaimer
For AWI and New South Wales DPI: you need to be able to tailor what's best for your enterprise. You may be doing mixed cropping and a whole range of other things, so even though I tell you in theory from insecticide resistance theory what's best to do, you may not actually be able to do that on your property.
So that's it for me.
Justine: Thanks a lot, Narelle. I'll just flick this back to me.
Efficacy issues
Sorry—okay, I'm back. Narelle, if you don't mind just keeping your mic on, we've only got a couple of questions and I'm not quite sure if anything else will come in, but I just had one where a chap was just asking: the results from the farms where there were efficacy issues with the products—were they already having suspect efficacy issues on those places for the trial, or did you find you got a real range of submissions? So people that had no idea if they had resistance to chemicals, or people that were actively having issues?
Narelle: We had representation from just about every group, and we did count that and work out the percentage, and that is in that final report.
Yes, there were some producers who were struggling and were well aware that they'd had issues for several years. We had some producers who considered that they had no issues at all but were just interested to find out, so decided to collect a sample and put it in. So we did have representation from all of those.
I must say, even though we found 100% resistance in New South Wales, some producers were still saying that they were happy with their treatment—they were receiving the protection period that they expected from that product. So it is very much about: we look for that genetic change, we look for those individuals where that genetic change has occurred. These insecticides are put on at high concentrations and then they degrade, so it's that length of the period over which it degrades which gives you the protection period. When that change has occurred, at the beginning there should still be sufficient there to kill—it's just the length of that protection period that may be reduced if resistance is there.
We saw this with the OPs—they started off giving about 16 weeks' protection, I think, and in the end they were giving less than four. So it's not a new story—we're very used to that, not just with OPs but crops and a whole range of different things—worms, everything. Yeah, I mean, it's just what happens, isn't it, when you've got an animal with a very short life cycle. Virtually insects are fabulous—they'll be around here when you and I aren't, Justine [Laughter].
Winter blowflies
Just two very quick questions: if I'm seeing blowflies during winter and I know—I just think it's time, it's not quite 15 degrees yet—does that mean they will still reach adult stages regardless of these environmental conditions? So I suppose they've been getting strikes in the winter but would think that the environmental conditions weren't possibly warm enough?
Yeah, and I must say it's incredibly interesting. Over the period of time when we did this study, there were only a few weeks of the year when we weren't receiving samples from somewhere. So there seems to be fly strike going on somewhere—you know, there's favourable conditions somewhere just about most of the year. In those southern states—and this is why I think in those southern areas—I think Victoria is probably better off than New South Wales because they have a colder winter and you actually put that stop to the population and they go into the ground.
When they're in the ground, they are actually vulnerable. They are vulnerable to being flooded—if you get rain, they drown. They're vulnerable to being eaten by other insects like ants or a whole range of different things, so you can knock your population down during that time.
Fitness modifiers
There is a thing called fitness modifiers, and when a resistance has been present for a while, the insects get other genetic modifications that mean that the resistant individuals are as fit as the susceptible ones. Often these resistances, when they occur—they might be resistant in the presence of the chemical, but when there's no chemical, it may even be a lethal gene, like they may not be able to survive. But once they've selected these fitness modifiers, they are environmentally fit as the susceptible ones, and you don't get that knocking of the population like that reset on resistance which you get with chemicals that haven't had resistance where fitness modifiers have been collected.
A study was done in 2012 where the overwintering population was looked at, and the flies down in a very cold area of New South Wales—the flies that were in that first emergent slot—were found to be dicyclanil resistant. So that tells us that they're not getting knocked off during that overwintering period.
Rainfall and protection period
Okay, and then just the very last one is: what sort of level of rainfall do you think would be almost high enough to have a significant bearing on the protection period? Are we talking about, like, really big rains?
Well, this is the thing—like I said, a lot of people have tossed a lot of calculations and used a lot of different figures. It very much depends on your sheep, the length of your wool, whether or not you used a water-based or a non-water-based formulation. Some of the products claim that the chemical becomes locked in the fleece, so it really very much depends on your fleece, your sheep, how much protection they can even get in your paddock, or whether they're just out getting totally drenched all the time. There's a whole heap of variables, so yeah—I wouldn't say how much anywhere at any time. I wouldn't put my neck out and say, really, no.
Closing remarks
Oh, that's great, Narelle. I think we'll let everyone go there. It was a really good webinar. I hope everyone enjoyed it, and thank you so much, Narelle, for giving up so much time. And everyone—I've been pestering Narelle for about two weeks, so the poor thing's been getting emails and things from me as I try and get myself organised. I'd also like to thank Leonie Coleman, who works in the NRM team for Northwest Local Land Services—she knew how to run webinars—and Jackie Grillman, who does all our communications and media and just joined us recently. They're in the background making sure I don't completely stuff this up. It wasn't quite the blind leading the blind, but I was definitely stomping around with a white stick for a while with this.
But thanks everyone for participating, and we're definitely going to send this out as a recording. I know quite a few people couldn't get on—it's always hard, or people have been diverted. I did see there were a couple of other little questions, but I'm going to get Narelle to just email you because they were very specific, Narelle—I think people having big issues—so I thought that might just be a better thing to deal with one-on-one.
But look, thanks everyone. There's a little survey at the end that just comes up when I click off this, and yeah—thanks for participating, and hopefully we can run something else in the future. If you came to learn a bit more about the FlyBoss workshop—the management tool—we're happy to try and facilitate something around that, but you've got to let us know if you do want to do that. Also, Northwest LLS will be doing a webinar on worms in the coming weeks because that's our other big summertime issue. I think it really will be worms, especially as we start warming up, because the old barber's pole gets cracking.
But the one thing I did take heart from, Narelle, was when you said that the pupae like to drown—or the larvae in the ground—so I thought we've had some good floods up here. So yes—sometimes people don't attribute to insects exactly the same things as yourself, like having to—but I tell you one thing—they've got it all over us. They can actually—the maggots can breathe through their bottoms, so they never need to stop eating. We can't do that, but there's an adaptation.
And thank you, Justine, for the opportunity—I greatly appreciate it.
That's right—thanks for all your time and help with it. Thanks everyone—have a lovely afternoon. Bye.
