 Hi, welcome to Tater talk on Tuesdays at 10. That's that's quite a mouthful to say Um, and he asked me here to talk about PBY spread a little bit. Um, you've heard Kent Sather He's giving you some pretty good news about about North Dakota Minnesota's numbers are fairly similar understand. So we had a good year for PBY in other words very relatively low PBY infections this year, not a lot of projections. That's good and It really does kind of underscore the fact that that you know, a lot of it sometimes is Dependent on the vectors. We had a very low vector year this year until late in the season But it also means that we're doing some things correctly and that's that's always good But let's face it. You know, if you ask me to talk about PBY You all know I'm an enomologist. You all know I love things with six legs and you know what I'm gonna talk about I'm gonna talk about the vectors. So today I'm gonna give you a little bit of background of PBY again Just to refresh your memories a little bit But I'm also going to talk about some of the information that we have now on what Regional vector populations are doing and how things are changing a little bit with our interpretation and what that Data what those data can actually tell us and inform us for management purposes So I'm gonna talk to a lot about aphids today And we all love aphids so much I know Our PBY epidemic here is part of a larger pandemic just like COVID Okay, globally potato virus wise most important virus of seed potatoes It's a problem in every seed growing location in the world that I know of But we're also we're also getting a pretty good handle on how this Epidemic works. We're getting a pretty good handle on Improving some of our management options starting with clean seed controlling vectors a lot of the stuff We've done for a long time also minimizing mechanical transmission, which we're now realizing is is Maybe a larger problem than we originally thought But there are still some issues that make management a little difficult We've got new strains that are becoming more and making up more and more of the Virus that's present in in our regions and a lot of things like well PBY Wilka Which is becoming probably the major virus that we strain a virus that we're seeing certainly in Minnesota And in the area you want to go to as well. And so these things are harder to see they're harder to pick up when you're scouting for For PBY so they're harder to rogue But just as importantly or maybe even more importantly, they're actually easier easier for the for the Vectors to spread so these are easier to transmit than those other vectors. So PBY O is you know, not very not very numerous anymore most of the Infections are PBY Wilka for the last couple of years, but The reason for that is the aphids themselves and vectors themselves are Transmitting these new varieties more easily than some of the older ones PBY is a non persistent virus. Most of you know all this. It's just reminders By non persistent they're talking about in the vector not in the plant. So persistent virus After an insect Acquires it and sucks it up in the sap It's got to go across the gut membrane and build numbers and finally get to the salivary glands of the insect before it can transmit it So for potato leaf roll virus, which is a persistent virus It could be up to three days before an aphid actually picks up that virus and is able to transmit it to a non-infected plant That's a good time. It's a good time period Consequently, we can control this potato we can control Persistent viruses with traditional insecticides ones that cause mortality neurotoxins like pyrethroids and neonics and things like that That are targeted at killing the insect But might take a little longer to do it might take 24 48 hours to kill an insect that way with once they're exposed And so a non persistent virus it takes so long to get to the point where it can be transmitted again You may be able to control that spread And sorry persistent virus a non persistent virus So that's one that an insect can pick up in seconds and transmit in seconds now with PVY and aphid actually Some of the times say less than a minute, but even the long periods are Five to ten minutes of feeding will allow them to pick up PVY and in fact the time that takes for this for an aphid to pick up PVY virus Really has a lot to do with how much virus is in the plant how effective that plant is and what the virus concentration is Once the virus Is on the mouth parts of the aphid it can now transmit that virus It's what we call viraliferous that point it land on another uninfected plant and once it probes The virus particles get wiped off and now they're in the uninfected plant the plant is now infected So it's a very rapid process the Some species are a lot more efficient at it than others Some of them the virus particles really stick well to the to the mouth parts and they're easily transmitted Some of them as a matter of fact like green peach aphid will remain infectious even after the next feeding Most species though once they've got these pieces of virus on their mouth parts They use those mouth parts to pierce into another plant those that virus those virus particles get wiped off And so once it's been on an uninfected plant transmitted the viruses that aphid is clean But it can pick up virus particles from an infected plant a separate infected plant very rapidly So there's no limit to how often it can become infectious with an unpersistent virus Because the transmission time is so short it means that if you've got an insecticide that takes 24 hours to kill an insect Or even an hour to kill an insect That's still long enough for that insect to transmit PBY and consequently we don't get really good PVY you know suppression of PBY transmission PBY spread with traditional insecticides. There are some insecticides that work on feeding and stopping feeding and probing behavior And those are a little different but using the traditional insecticides. We just don't get great control Vectors are the vectors in other words the little insects that are transmitting this disease Those vectors are principally winged aphids and they're moving from plant to plant and winged aphids are different than the aphids You find on plants, which are non winged You're gonna find two morphs out there winged aphids and non winged aphids You find the winged aphids are a little larger. These are green peach aphids. These are the bad girls right here and Little bit of information on life history Through the summer there are no male aphids, you know, I've always told that story and you want to make a buck That's somebody a buck. You can tell what species it was sex and a busy whole up. Oh, that's a female Yeah, they're all females. So just an old anemology trick. Don't ever take that back from me So there's no males out there. They're all females. They also don't lay eggs They they give birth to live daughters and they're basically born pregnant. So it's all a cloning thing They're basically putting off the same genotype as the mother has itself There's no eggs and this is one of the reasons why aphid populations can expand so rapidly Now winged aphids they live a different life than the non winged aphids. They have a different job a winged aphid Her job is to disperse go to a new plant and found a new colony In the springtime the way these things overwinners usually the overwinners eggs on plants since springtime those eggs hatch They're all female aphids. They're not winged and they'll feed on the plant for a little while And then after a couple of generations you get a whole generation of winged aphids and they leave that overwintering plant and they go to the summer hosts Most of the time those are different species When they get to the summer host The winged aphid will fly into a field it'll see the the summer host It may be attracted because of reflectance or any one of a number of things it'll land and the first thing It does is it probes the plant and the reason it probes the plant is it because it wants to taste the plant and find out Is this a suitable host if I leave a daughter here? Is she going to survive? If it is a suitable host, that's exactly what she does She deposits one or two daughters and flies off to a nearby plant another plan to test that one That daughter is always going to be wingless because a wing because a wingless aphid a non winged aphid their job is to build the colony and So they're not interested in dispersing they're interested in feeding and taking that energy and turning it into growth and reproduction And so if a winged aphid gave birth to a winged aphid, it wouldn't found a colony It would start flying on itself. So a winged aphid always gives birth to a non winged aphid a colony builder If that winged aphid lands on that plant and probes it and decides this is not a good host It just leaves it'll fly off to a nearby plant And the interesting thing is I have never met an aphid that has a degree in agronomy or any experience in farming at all So they don't understand monocrafts in the least They land on a potato plant in a potato field. They'll taste it. They'll say, you know, if it's not if it's a soybean aphid or something Oh, this is not a host. I'm not going to leave a daughter here And it flies maybe a meter or two meters at most and lands on another potato plant and goes I wonder if this is a host and probes it So they don't really have that thinking ability. You're never going to see an insect shaking the king's weed and saying thanks for the Nobel Prize It's not going to happen And so, you know, they're they're operating on Hardwire behavior and they're just going to hop plant to plant to plant all the way through all the way through a field Leaving daughters if it's a suitable host and not if it isn't There's another factor we have to think of and that's what species of aphid has entered our field Some of them are going to be moving in some of them are just passing through The ones that are moving in are colonizing aphids. They're going to leave a daughter She's going to start feeding and leave, you know, leave a bunch of of individuals Those are the ones you're going to find little colonies of on those bottom leaves when you're out scouting for aphids The other ones those are non-colonizing aphids like soybean aphids cereal aphids Those ones are actually going to fly in probe Not a host move on to another one. So those are the ones that'll fly their way through an entire field Here's the thing if they're picking up if there's any inoculum in that field And you have an inflight at one of these non-colonizing hosts They're going to move that inoculum around Because they're going to be probing picking up virus going up not a host fly over To three meters probe another plant up not a host. It's just deposited any virus picked up So as they move through They can be a big problem in fact the non-colonizing aphids can be as big a contributor to the epidemic If not bigger than the colonizing aphids will so inoculum is going to get looped around by these individuals It's just one of the other things that we have to think about The non-colonizing individuals is one of the reasons especially things like cereal aphids is another reason why we started this the aphid alert You know years ago in the 1990s and we started it up again in 2012 This was actually to just to look at whatever was flying into the to fields and we've got about 20 traps set up between North Dakota and Minnesota and We have grower cooperators who know it and many of you who are watching And I really have to thank the grower cooperators without them. This project is not possible period These cooperators will they go out and they change the trap jar They seal it up. They mail it to us and we sort through the bug soup pick out all the aphids And then we identify all of the aphids that are going to are capable of vectoring pvy We also calculate something called a pvy vector risk index and that's so we can standardize results across Across all of the species of aphids that we're counting and figure out what the actual risk of transmitting pvy is based on the numbers those aphids The reason for this is not all aphids are created equal when it comes to transmitting pvy I've already mentioned that a little bit and some are not very efficient But still we'll move pvy around if there's enough of them in a field Others like green peach aphid if they're in a field and there's an oculum. They're going to move it around So um If you think about risk Well, hazard is the innate danger of something, you know Because of a characteristic of something and risk is hazard times exposure So aphids have the biological ability to transmit pvy virus. That's hazard But if they're actually present in an area and they have the opportunity to transmit pvy That's risk and so we wanted to talk about what's the chances Of of these aphids these particular aphids that you've got coming into an area What's the chances they will vector pvy? So to calculate out this risk index what we do is we Look at how many aphids of particular species they are And then from the literature we get how efficient a vector are they compared to green peach aphid because that's what everybody does When they look at vector efficiency, they can't pair everything to green peach aphid because it's the benchmark There it's the most efficient vector there is So what we're doing is if we have a species that's maybe one tenth As efficient as pvy and we read that in the literature What we'll do is we'll say okay, we got 10 of them. That's the equivalent of having one green peach aphid So you can think of the vector risk index as everything in the terms of green peach aphid if you want to think about it that way So that's why we do this so we can actually look and calculate how bad things are or not how bad they are what the potential risk is um Because we've been doing this now for nine years uh 2012 through 2020 inclusive um We're able to now start looking at regional patterns Now we don't have a full nine years from all sites But we do have enough from most of these sites that we can multi years that we can start to think about What our regional patterns are going to be like so Even though individual locations in a particular year might not mirror the regional pattern We're actually going to be addressing that we'll be developing these local patterns based on kind of clustering some of these sites together We'll make that stuff. We'll make that information available on the website And the reason we're thinking this might be really useful to producers is it gives us a lot of information on timing our management For example, it tells us when we're at the greatest risk in our area We fill in the best time to scout and best time to use different scouting tactics When to be really vigilant about management when to think about specific tactics, and I'll talk about each one of these as we go along Well, if you look at that average data from 2012 all the way through 2020 Um, and you look at when we've been capturing the aphids in the total number. This is just the total vector capture Averaged per week across all traps for that entire nine years and what we find is Our aphid numbers our aphid vector numbers don't really start to rise until about the middle of july Now these dates that we've got down here. These just the numbered of the dates These are iso weeks so that we could compare across years So we have standardizing the time And what we see is we have our populations start to rise in july Peak in august and then they dip down to september Now we don't have as much data for september as we do for june july and augustin But that's okay because by that time most of the producers have started to bind kill bind kill is probably well on its way And so we're less concerned about what whether the vectors are out there because there's nothing to transmit pvy too, hopefully so We'll probably look at that as as time goes by but for now We're happy with with knowing when we're getting our greatest number of pvy vectors Well, not only do we have the vector numbers, but we know what species they are So we've been able to calculate What's the risk over those times? What's our average risk over a season? And that's a little different and it probably is related to the different species presence at different times So again starts to rise in july it peaks in early august You see a little slough and then it peaks again in the end august and then it just dips down That's probably because of the different species end of july early august It's typically when we get our big flights of serial agents and some of those are very effective vectors And so we get a little peak early august and then later in the year That's when we're going to start seeing stuff come off of maybe some other crops that are starting to senes Maybe canola some of those other things and so we get a peak then as well our um Amount of i'll talk about the cumulative pvy risk in a moment because it ties into something else i'm going to talk about Well, the usefulness of this data of looking at when we're actually getting some risk And when we're seeing our peak risk means that we can now start to apply it to our management tactics for example The new tactic that is coming out of work that's being done in in new brunswick Indicates that adding insecticide Specifically lamb to cyhalothrin the active ingredient that's in warrior silencer and Adding that or belief or fulfill the two anti feeding insecticides If you add those to a foil And you you do that application of that of that tank mix once a week You're going to get As good or better suppression of pvy Then applying just a foil alone twice a week. That's what their data says You know, I can't recommend it, but that's what their data says I haven't done this data. I haven't done this this trial. We are doing it this summer They they do recommend a weekly afeit A weekly a foil treatments and adding insecticide in five times a year and they do they say two in the early season One in mid season two in the late season That might not be the best fit for us though The reason I say that is if you look at when those afeit populations are around into brunswick They're starting to see their peak late june Early july and then their afeit populations peak in july and then start decreasing through august Their season Starts well their afeit season starts a little earlier than ours does out here on the on the northern plains So if you look at ours again our pvy risk index that when we're actually seeing a lot of transmission That's going to peak in august Our numbers start to rise pretty significantly in july but they peak in august So we may want to start thinking if you're going to follow that tactic You're going to do that you're going to add insecticide to your a coil You may want to give a thought to when you want to do it Maybe you want to do one early season because we do see we do see risk in june But maybe you want to back and load that tactic. That's going to be something you have to decide We'll have better insights to that as we get that regional data moved worked out as well that local data worked out as well Mechanical transmission one of the other things that that the new brunswick Group came up with was they were able to demonstrate that pvy spread in tractor lanes tractor Rows was much much higher than we initially thought and so again because we know when we're starting to see our pvy risk Maybe if it's possible You can Look at when you want to minimize Being in the field it may not be possible with time or you know, we've got Bunderside to put on but there may be ways of ameliorating that mechanical risk as well So again a lot of this is related to when we're getting our Our pvy risk and if you look at the accumulation How that that risk accumulates over the season Again, it does mirror when we're seeing stuff. We do have risk building through june But it really takes off into an exponential rise In july and then starts to plateau Middle of august out into september. It's when we start to see a little decrease and the risk starts to not add in as much What this means is maybe we want to think about when we're increasing our our pvy spread the most and maybe concentrating our efforts Maybe targeting some of that that temporarily I'm not saying again. You can't ignore that early season or the late season But it does mean when we're seeing that big rise might deserve more attention It also may be when say we start to adopt some of these different scouting techniques Which might be a little bit more expensive like remote sensing or liza sticks a lot of these things might be adopted in the near future Maybe the best timing for those is not you know early Maybe we might want if we wanted to If you're like me and you've got scottish heritage and your little parsimonious Maybe you want to focus some of those more expensive methods in particular time where you're going to see a big return But again, I wouldn't necessarily go ahead and recommend these right now these tactics right now Wait until we have some of that local data worked out So you have a better idea of when things are happening But it is worthwhile thinking about and it is worthwhile planning for in the future So i'm probably over time or at time. I will be around for questions So please ask if you've got questions. Thank you