PestFacts South Australia webinar – September 2026

In this webinar, we are going to talk about the spring pest watch from field observation to time right. This webinar is being delivered as part of GRDC funded seasonal status of pest and diseases for growers project. My name is Marame and I'm pestfac essay editor and hosting the webinar today. The Department of Primary Industries and Regions acknowledges the traditional custodians throughout South Australia and their continuing connection to the land, waters and community. We pay our respects to all members of the Aboriginal community and their cultures and to elders both past and present. In today's webinar, Dr. Martin van Helden will provide an update on locust activity, key spring pest and natural aid control by beneficial insects and then Ian Thomas from Cesar Australia will talk about time right and risk assessment and resistance in redlem >> my contribution to the situation in South Australia um in a interesting year as far as weather conditions is concerned so I will probably start by explaining that a little bit will the ideas are about this year's weather conditions and how that influences the pest status. Um, so 2026 a very unusual year. It's very clear. We had a very early break in February. Uh, and we've had follow-up rains in spite of the announced El Nino. Um, it keeps raining and it has been raining most of the time. Um, crops are clearly ahead compared to previous years because the sewing was done much earlier and the temperatures have been quite okay. So I think everybody is quite happy with this year with a yield forecast that's looking really good especially compared to the last three years which have been tricky. So um that doesn't mean that it's easy for anything that is pest and diseases. Um diseases is not my part of knowledge. So uh I'll let my colleagues from pathology work on that. Um we will be covering insects. Um so what we've already seen very clearly is that in 2026 with the early sewing there was also still an opportunity for aphits to come into crops um causing virus inoculation. And uh the big question now is how will this all work out on aphids and all the other pests that we can expect um but for which we have no idea about their population levels in the coming months. spring is only just starting. Um, and it certainly will be very interesting to observe and I think we need to observe to be sure what's actually happening. Um, so if you look at the weather conditions 2026 a very normal year as far as temperature, this is temperature anomaly from May and July. So very normal year in that sense. However, what was very different is rainfall. So this is the rainfall from May to July just taken from the bombside. So as you can see there's large areas of South Australia that have received between 50 and 100 millimeters rain more than they usually do. These are the August rainfall data um for all of Australia. Um as you can see we still have had quite a bit of rain in August. um large sudden downpours with some flooding events um which is still quite good for agriculture. I think no farmer is complaining about the rain. Um it might be different obviously at harvesting and would be still too wet but that should be okay. Um so for this at this stage we don't seem to have a very clear dry El Nino year. You can see we're very much above average in large areas, especially in the north, which is not really country, but more pastoral country. Um, and you can see that around Adelaide, um, it's it's quite a normal situation, I would say. Um, on the App Peninsula, they have a bit more rain than they normally have. So, they are certainly happy with the prospect of their harvest of cereals, um, and some other lentils and things like that. So high soil moisture in the outback however means there's a lot of green growth over there a large amount of vegetation and that in itself is potentially a risk for the cropping in this spring and I will mention a few cases where we think there could be an invasion coming up and we need to keep our eyes open. So aphits and virus I think that was very clear at the start of the season when everybody started sewing uh early normal seed treatments applied and then all of a sudden there was aphits coming into the crop because it was warm enough they had had time to build up. Um they moved into the crops and unfortunately the seed treatments are not that efficient anymore. Um so um yeah there was quite a few aphits. If you now look over the winter period from the reports that we get in from farmers and aronomists, it seems that the aphit population would say relatively stable. We haven't seen huge outbreaks. Um there's aphids around but not huge numbers. However, what we do see is that there's actually quite large amounts of natural enemies building up which is very positive. Uh just here on the bottom left side, you can see a yellow sticky trap that we had up in Turretfield couple of weeks or two months ago. I think it was this one. And all these flies that you can see here, all roughly the same size. These are all hoverflies. So they come into the crop and they will lay their eggs near a maggots of the hoverflies will eat the aits. So we think that even though there was high aid pressure at the start of season, we think that at the moment the parastoids and the hoverflies have very well taken over and probably some other natural enemies. Um so we think that the regulation this spring will be better than it usually is. So take a look if you do your observations monitor your aid population but also look at the presence of natural amies because it'd be a pity if you would go in spray let's say cabbage aid while most of them are already parasitized. We had of course a high early virus pressure on canola and potentially also in lentils that could be affecting the yield. Unfortunately there's nothing you can do against that. Um that has happened before the winter. um spring virus infestation if it would happen now has probably very little impact on the yield because the crops are much more advanced. So even if they would get the virus now they would not have a huge yield reduction probably even no yield reduction. So I would not be too worried about a few aphits transmitting virus in the field at this moment. Green peach aid should be quite well regulated by natural enemies. Um that's a different story. Um diamondback moth we have very little reports. We've had quite a few reports of early infestation. Um, but over the last few months, we've had little or no reports of DBM. We think it's probably the same situation that natural enemies are doing a good job. Um, but keep an eye open, of course, because DBM, if there would be a high infestation in the potting stage of canola, then potentially you can have yield loss. So, look at that very carefully and make sure that the populations are not too high. ETLA is one of those um crop specific issues um little caterpillars that start flying around this time of the year. Um so we do have a model that allows you to see when you should start monitoring and it's actually in most cases around this time sometimes even a little later. Uh if you go to the internet and you just look for ETL model, you can enter your own data of where you are and you can see how much heat has been accumulated and when you should start monitoring. Um certainly don't spray because the model predicts it's the highest level of population because we have no idea and so far as far as I know we've had zero reporting of ETLA. So keep us informed and um spray only if you need to. But worms um we had some issues at the very start of the year with some lesser butwarm. Um these are migratory species that usually come from the outback. So potentially this year they can be building up in the outback to quite high numbers. Then the question is will they start building up and will they start migrating? If they have enough to eat, why would they migrate? So I wouldn't expect them to come in automatically. And we do have of course the native trap bloodworm trapping going on and that's being reported on pests and also on X regularly by Mariam. So far we haven't seen much. So um but it's still a bit early in season. They basically is keep monitoring use your sweep net um which is the best tool at this time of the year to monitor for most of the diseases also pest that can be around. Another caterpillar that we did get some reports in quite recently is the common army worm. So it's a native species. We're not at all talking about the fall army worm because that's not a problem in South Australia. It's just too cold here. We're not expecting that to establish and we haven't had any reports so far over the last few years. Um but yeah, the common army worm is a little bit of a different insect which again can migrate and can start to build up at this time of the year. So the adults are usually active in August and September. Um they will lay eggs, the eggs will give lavi and the lavi will mature in November and December. Um that's where you can potentially have some damage especially if they start nibbling off the heads of cereals and things like that. So be very careful. Do your observations and decide on whether or not you think you should have a chemical intervention. Last issue and and probably the most worrying or at least the most um unsure um is the situations on locust. So if you remember well in April May there were some reports of Australian plate locust on northern EP and in the riverlands. So they were adult locust migrating into these areas. They had been building up in the outback. Very unusual to have that at that time of the year because normally it comes only after winter. Um, so these locust have been around there. There's been a little bit of egg lay as far as we know. Um, but the big question is what's actually happening in the outback because that's where potentially populations can build up. Um, for those of you who are around longer than I have been in Australia, uh, if you still remember 2010, huge outbreaks of locust. They had been building up in the outback. It was also a very wet year in the outback. So they had been building up to high populations then started to migrate um and then they can cause issues when they when the adult locust arrive in the cropping country and that's really difficult to control. So at the moment you might be saying why is he talking about lo because I haven't seen any. Well that's normal because they are in the ground at the moment they're overwintering in the exchange. Um we work together with the APLC the Australian plague locust commission and biocurity. um to monitor the possible hatching of eggs and the densities that will uh occur and we will start doing that in September. So next this week actually and next week um especially in the northern fenders ranges where we expect them to hatch first. Um, and then the question is how will they build up their populations in the outback and will they build up to populations that basically eat everything there and then they will start migrating. So we still probably a couple of months away before the problem might arrive in the cropping country and we're trying to do everything to avoid that actually happening. So they would have to do at least one and possibly two generations before they start banding as it's called and migrating into the cropping areas potentially into the cropping areas depending weather conditions. Um but yeah you it is possible that it would happen by late October. So there is already a lot of things going on. You might not be aware of that, but there's a whole bio security preparedness team and also the Australian plate locust commission that are preparing monitoring in the outback. They are preparing for possible control, especially in those areas that are not accessible and also nature reserves and things like that where fortunately we do have biological control agents that we can use. Uh, and as you might have seen, there's also a pesticide rebate scheme for growers that's already been announced. Um, it's a bit early to decide on that now. I would probably wait until middle of September, end of September when we get the reports on how many locusts are actually starting to develop in the outback before we have a better estimate of potential risk for the cropping areas. Don't forget the pesticide used for locust are broadspectctrum insecticide, so they will kill basically anything. um they only work when you spread them directly on the insects when they are present in high numbers. So yeah, you need to unfortunately wait until they are there before you can start doing something. Um but I can also understand that you want to be ready if they would arrive to be able to do something. Um there's a persa site if you type in Australian plate locust persa you will come to that and there's also the APLC Australian plate locus commission bulletins which are available there which can give you quite a bit of information for example this is the prediction of the hatching date for the Australian plague locust eggs. So, as you can see, uh this is all of Western eastern Australia. Um as you can see in in South Australia, um most of the hatching in the northern Flenders range would probably be second half of September. And uh if you go down to the Riverland, it's probably only end of September before the first eggs will start hatching. And that's when we will get a better idea of how big the pressure is. But yeah, we we certainly don't want to go back into what we've had in 2010 when there was huge flights of locust. And if there's a huge flight of adult locust landing somewhere, they will eat everything that's green. So, we're trying to do our best. If you are a land owner in those areas, you should probably certainly be prepared and try and do your observations and follow the observations that are being done and will be reported by the APLC and by Persu. um you are asked to report sightings. It's a pest that you should declare. So on the left bottom you can see the exotic plant pest hotline. That's where you can call and um report the sightings of locust if you see any. Um it's it's probably still a bit too early. We expect that in two or 3 weeks to maybe start some little nymphs to hatch and before you see them they probably need to get a bit bigger. But yeah, um we will keep reporting on that through person spring with quite a bit of uncertainty. Um I would say stay alert, don't be alarmed. Um monitoring is key. Get your sweep nets out, go through your crops regularly. Um and be very aware of natural enemies because we think this year natural enemies are very active and you can take these into account to control populations of things like aphids, DBM, and even some other stuff. So for the locust probably wait a little bit look at the APLC and first updates report sightings if you see any especially in areas where adults were present in May where potentially they have laid some eggs. I don't think that'll be providing the large numbers that cause problems. They will be coming from the outback and that would be only in October. Um like I said locus insecticides are really not very nice insecticides really broadsp spectrum compounds. The only exception is green guard which is a biological product but that's a little bit tricky to apply. So um that's probably not something you as a farmer would use. You probably would go for some of the other products. Um very important these products you cannot apply them before the locust are there. You have to apply them on the banding nymphs on the ground. It's contact chemicals. Uh there's no use spraying before the locust are present. you will have no effect because the products don't stay active very long. So, yeah, it's it's unfortunate, but you'll have to wait, see, and be ready to react if it comes through quickly. >> Yep. As Mariam said, my name is Ian Thomas. I'm uh um an extension professional for Caesar Australia, and I'm here to talk about managing red-legged earth mites using the time rat system, uh performing risk assessments, and the current resistance profiles that we see uh in the environment. Um, so to effectively manage red-legged earth mites, the main thing we need to understand is their life cycle. So, as as I'm sure everyone knows, they hatch out in autumn when uh conditions are sufficiently moist and cool. Uh, and then they will have uh four three or four generations uh of egg laying um mites during the cooler months. Uh but towards the end of the cropping season, uh they'll start producing what we call diipause eggs. Uh, and these are tougher, hardier uh, eggs that will allow them to over summer uh, and survive the warmer months. They actually remain within the the corpse of the mother when when she dies, which I think is a really cool survival uh, technique. Um but understanding this life cycle also lets us to exploit it um to control their population numbers because if we can target mites right before the last generation of mites right before they start producing diipause eggs we can reduce the number of eggs in the environment ready to hatch the following season and that's the heart of the time right system. So, uh, Timer functions as a website. It easy enough. You can access it via this QR code, um, or at wool.com/timeright or by googling timeright. Any of the usual ways you find things on the internet. Um, you'll be put dropped on a landing page that looks like this. um which uh you'll have to scroll down a bit of a ways, but you'll eventually come to a little uh bar where you can enter a your postcode in there and then that will provide you with your time right information. Um, before I show you what that looks like, I'm just going to quickly jump on to uh Caesar's involvement in this in recent years because Timer was originally developed uh by AWRI, MLA, uh, CSRO and GC um, 20 years ago. Um, but it was recently updated. Uh and that update has changed the underlying mathematical model that uh calculates the dates of the different regions and in also has altered what um climatic information is included to better reflect uh current climatic conditions and changes that have been observed over the last 20 years. Um the upshot of that is that this has shifted dates. Um so in most regions across Australia the dates have moved uh earlier in the year. So here are just a few examples. So in some areas the date shift has not been huge. So Port Lincoln here for example uh we're seeing a shift from the 18th of September to the 13th of September but in other areas such as Ararat in sort of central Victoria or over in Esperence you've seen two to three week shifts in the dates and pretty much everywhere those dates have shifted quite a bit earlier. uh Caesar has been for the last couple of years and ongoing for the next couple of years for the lifetime of the project I work on will be assessing uh a number of sites in a variety of areas across Australia to compare the old time right dates to the new time right dates and so far the results are showing significantly higher levels of control uh using the new dates versus the old dates. The other um shift that you'll see with the new information is a bit more evident in the way the data is presented here. So once you've entered your postcode on that website, you're going to end up with a uh a chart like this presented to you. Uh so this is the chart for Buckle Boo um over on the air peninsula. And in Buckle Boo, you can see the best spray date for time right is uh your time right best ideally. Um, but the new system also provides a best spray, an ideal spray window. So, if you miss that best spray date, um, or if it you think it's going to uh coincide with unfavorable conditions for spraying, um, you now have a window of opportunity that can be anywhere between 3 weeks and up up to sort of four or five weeks. Um, where you should still, if you spray, you should still achieve, we think, about 95% control. um as long as it's sprayed, you should get that high level of efficacy as long as it's sprayed within that window represented by these gray this gray sort of section here. Um so this allows you to if you miss your time dates still understand that you have a bit of a uh a time to get your um sprays out and still achieve high efficacy. If we move over to Keith now, sort of closer to the Victorian border and and and and down and east a bit, um you'll see that their spray date, their their best spray date is not coming up until uh the 6th of September and um with their spray window extending all the way out to the 21st. So, they've still got plenty of time to do an assessment and uh and put out a control if they need to. Another thing to note when looking at these dates is this system is has been set up and designed for pasture. um not necessarily this system hasn't been this model doesn't account for other cropping systems. Um so the next step is I suppose deciding whether you actually need to spray on that date and the first thing we recommend there is to perform a risk assessment. Um there's some more resources that I'll provide you later on that will help you um perform those risk assessments, but boiling it down to what we think the the key factors you need to be looking at this year are um uh is dividing these into what we know for this year and what we can think about and predict for next year. So the main one and the number one uh factor for this year and determining whether you should put out a time right spray is might numbers. It's just if are you seeing them out there? Are they causing the damage, the silvering damage you can see in this image here? Um, are they higher than normal? Are they difficult to control? Um, uh, that's going to be your overriding, uh, driving decision, uh, point there. And that's because the more mites you have, the more diipause eggs are going to end up in your system next year, ready to hatch. Uh, another thing that can increase your risk factor is, uh, and this is a tricky one, but it's a soft finish to spring. So, if you're going to get a milder uh longer, wetter end to spring, uh that will increase your number. Obviously, no one can predict the future, but it's something to consider based on the information you have at hand when making a decision as to whether to spray. Uh the next set of factors are the factors for next year. So, things that we can predict or change or control are crop type. canas, clovers, forage brasacas, and medics are all more susceptible to are all quite susceptible to um red-legged earthmite. So if you're moving a system into say from pasture into canola, you may consider a time right spray because you want to reduce your risk there. Um uh less susceptible crops include legumes and chickpeas. Um uh the second factor is is the paddic going to be burnt over the summer. So burning your stubble will uh um uh kill diipause eggs. They tend not to survive that. So that will significantly reduce your risk and may affect whether you want to put a time right spray out uh prior to doing that. Uh another is time of sewing. If you're planning on sewing very early next year, um more than a few couple of weeks early, but you know, if we're talking about sort of three weeks to five weeks earlier than than uh emergence, uh sorry, then then red-legged earth might hatch, you might uh that that will significantly lower your risk as well. So, those are all factors to consider when looking at sort of trying to introduce um time right into a system. It's not just about finding the best spray date and then always spraying on that date because if you spray on a time right date, you're probably not going to need to spray the next year hopefully. Um, moving on to the next factor is um the resistance profiles that are present at the moment in the environment. So resistance uh was first detected in 2006 uh and has been increasing steadily over time and it's particularly common in parts of South Australia and across Western Australia. Um so the first map here we have shows resistance to synthetic pythroidids. So the each one of these is a data point for a population that Caesar has tested um with uh um susceptible populations coming up in blue and resistant populations in orange. So as you can see there's a fair bit around. Just because there is a resistance in your area doesn't necessarily mean you have resistance in your paddic. Um however it does significantly increase the chances that you've got resistance in your paddic. Uh and we see a very similar story when we look at organo phosphates um except that the resistance there extends a little bit into Victoria as well. Um yeah, so understanding what you still are capable of spraying is good. And in the best management practice guide that I'm about to talk about, there are some chemical windowing strategies for people dealing with different um resistance profiles. Um so resources that we have available to use for everybody that are Caesar produced or produced in conjunction with Caesar. Um the main one we have which we recommend to everybody is the redlegged earth might best management practice guide. So if you wanted to grab a quick screen screenshot you can use that QR code there to access a digital version. Um, I believe you can uh call up the printer and request a version uh if you like or you can just Google redlegged earth my best management practice guide which if I'm being honest is how I access it 90% of the time. Um, other resources we have include the time right tool we've been discussing today. But if you are hoping to get your local population tested for insecticide resistance, I recommend uh contacting Dr. Aston Arthur, my colleague um who would be presenting today except that she is currently out in the field um collecting red-legged earthmite samples for resistance testing. Um uh bear in mind that the ter the time frame on these isn't super quick. So you are unlikely to get uh results back uh in a timely decision in order in in a timely enough frame to um timely enough frame. Yeah. To um uh make a decision for this season. Uh however um for synthetic pythroidids, Caesar has developed a quick infield test for uh a rough and ready test for determining whether you might have resistance to synthetic pythroidids um which can be performed using plastic containers and common things you will find lying around your property um or your client's properties. Um and yeah, so those are the tests uh sorry those are the resources that we've provided to help you manage radites and we hope this has helped you make that decision and thanks. Oh and I'd just like to say that the project is funded by JC and run in conjunction with WD herd. >> Are there any biological control option for redleg mites? >> Uh yes so that's that's a tricky one. Um we know that certain predatory mites such as uh French mites and snout mites do feed on redlegged earth mites. Um however in most circumstances the population numbers are not high enough for effective control in a broadacre system. Ways you can encourage those um a big one is maintaining shelter belts uh along fence lines and between paddics to just keep those natural populations high. We also know there are probably a dozen or so other generalist predators that will be feeding uh on red-legged earth mites at the moment. Um there are things like uh certain mites that are sold commercially um but none are listed like uh in Australia specifically for redlegged earth might control in a broadacre system or in a pasture system. Um the loss of the chemistry is a real problem uh for us at the moment. So as part of the project uh I work on we are testing some novel chemistries uh and obviously we'll the results from those will uh be coming out in in the future. Um we don't have the results from them yet. Um and uh we're also doing gut content analysis on generalist predators from a few different sites to try and get a better understanding about what is eating them in the wild. Um but yes at the moment there aren't really great populations. That's one of the reasons we push the time right model so hard is that when used correctly and in conjunction with risk assessments um it should significantly reduce the uh requirement to spray particularly spraying multiple times a season and um uh allow sort of us to extend the shelf life of those chemistries so that we're not losing them um and uh and hopefully that we're not putting as many of them