 So I'm Anthony Hansen, I'm a PhD student at the University of Minnesota and I'm also originally from Bruton, Minnesota, grew up on a farm. There's come from beef cattle background, different forage crops, and standard field crops as well. And my work involves host plant resistance, using that against soybean aphid. So this talk will cover just a general background of host plant resistance, what's available for farmers, and then specifically my research that the SARE organization provided a grant for. So it'll be kind of a two-part area. So to start off with soybean aphid, I'm sure most people are familiar with it, but if you're not, it's our primary soybean pest in the upper Midwest. It's primarily problematic because it can reach high population densities, it can reproduce really quick on a soybean plant. And there are a couple different control methods. The main one is insecticides, and that's pyrethroids and organophosphates for conventional use primarily. And application of insecticides is only recommended if you go out in the field and scout, and you find aphids out there. And if you get to the plant where you find, on average, 250 aphids per plant, we call that the economic threshold when you're supposed to start looking into applying insecticide. And that's to prevent aphids from reaching a higher level of infestation called the economic entry level, which is 675 aphids per plant. And that's when the amount of yield loss those aphids would cause would justify an insecticide application. So that's one method, but one other control method that's showing some promise is using host plant resistance or resistant plants, and there's a couple different ways that plants can be resistant to an aphid or another insect. The first is called anti-biosis, and this is basically a fancy way of saying that there's some chemical in the plant, some compound natural defense mechanism that will reduce an aphid survival or reduce its reproduction on the plant as well, so you see lower population growth there. Another one, oh, okay, another is anti-sinosis, and this is basically repellency. So an aphid may not be as attracted to that certain plant, and there may be other factors in that plant that it's actually a physical barrier, such as trichomes, and those are those little hairs you might see on the underside of the leaf. A plant can have a lot of those and actually act as a defense against aphids trying to get onto the leaf and start feeding or laying nymphs. And there's a few different genes that have been found so far that will provide either anti-biosis or anti-sinosis, and they're called rag genes or resistant aphisk lysines, and they've been found by looking at other plants in Asia where the soybean aphid is native to and screening those for resistance, and then if they find a resistance trait they'll breed that into the current varieties we have here. And I'll be referring mainly to rag 1, rag 2, but just keep in mind that there's a bunch of different rag genes, so if you're looking for soybeans that would be resistant to soybean aphid you want to be looking for something that says it has rag 1 or rag 2, and that'll be specifically that it has some kind of aphid resistance. So this is just an example graph showing how resistance works. This graph shows mean number of aphids per plant so many days after infestation. So a susceptible plant will have aphids on it that will steadily increase in population and they can reach high levels in this case it takes about 1,400 aphids. A resistant plant like these two at the bottom you won't see, you'll barely see any population growth on those plants, they'll either be a flat line or it's a very slow population growth. And this is just for a very short snapshot. At the end of the growing season you can look at how many aphids you had total over that whole season. So one concept I'll be using a bit is cumulative aphid days and for those that aren't familiar with it it's just kind of a accumulation of over the entire season how many aphids that you have. So more cumulative aphid days, the more aphids you have. And this graph shows different varieties that either are susceptible, they don't have a resistance trait and then there are others that are just one resistance trait such as rag one or rag two. And then you can have what we call a pyramid which is two or more resistance traits in that same plant. And this graph shows high cumulative aphid days for all these susceptible plants in various locations and years. So these different colors show say Minnesota, South Dakota, etc. in different years. And when we go to resistance traits we can see that most of the time there are fewer aphids and they're below the economic threshold, this red line. But there are some cases where you might have a resistance trait but you still have aphids reach damaging levels. And you can see just a little bit in this graph that there's very low aphid numbers on that pyramided line. So that's an important concept thinking about if you're going to be getting a variety. If you find one that's pyramided that will help you out especially with yield. Because like this graph shows this yield loss if you have a susceptible plant you're going to lose a lot of yield. With rag one or rag two alone you do get some reduced yield loss but you still can see yield loss. That pyramided line you see next to no yield loss. So thinking about different genes that are being involved and the varieties might be interested in that's always an important thing to think about if you're planning ahead for next year or this year I guess now. But so one reason why a single gene trait might be overcome by aphids is by what we call aphid biotypes. And there's a few different biotypes so we call them biotype one, two, etc. We call biotype one a virulent which basically means if that aphid is on a resistant plant it's not going to do so well but something like biotype two it will be virulent which means it can overcome resistance specifically to the rag one trait. And there's a few different other cases of biotypes and you can get to one like biotype four that can actually overcome those pyramided lines. So that's justification for actually finding new sources of resistance and pyramiding more of those genes together. And that's part of the work that we're doing at the U of M right now I won't be presenting on that but just screening through a bunch of different lines trying to find other traits we can breed into lines that either will be publicly available or that other breeding companies will use. So transitioning a little bit we're talking a little bit about insecticides at first and then also resistant plants. So one concept we're thinking about all those together and I'll transition into some of my work is integrated pest management. So we're wanting to use different control methods as best we can at the right time and try to reduce any like non-target effects on insects that we want to have around in our fields. So thinking about insecticides it's the main control method there are a couple issues that come up with that one aspect. We actually have some issues with some organic insecticides that organic growers can use is that they don't seem to work that well for soybean aphid and that's what we've been hearing from folks in the field and seen a little bit which I'll show later in our experiment. Then also overuse of insecticides in general that can have non-target effects on your natural enemies like lady beetle or parasitoids and you'll hear more from George Heimel about that after my talk about just natural enemies in general. Then also for resistant plants one thing we've been finding is that it's sometimes difficult to actually find varieties that have those resistance traits and they've been on the market since 2009 but that's been a little further down south up north here where we have early maturity groups it's been a little tougher to find resistant plants and just looking through seed catalogs even around here I haven't seen too many companies that advertise aphid resistance but there have been a couple here and there so you might have to search for it a little bit. So that leads into my actual research project thinking about what happens when we combine both host plant resistance and insecticides and in this case I was thinking about if you have a resistant plant is that going to increase the susceptibility of those aphids to other insecticides but that could also be flipped around the same maybe their susceptibility might be decreased or there might not be any effect at all. So that's the general research question we're posing and I kind of have just some graphs to kind of show the concepts of what we're working with a little bit because we're talking about interactions a lot. So this graph shows susceptible and resistant plants but then also and the white is if you had no insecticide treatment black is if you use an insecticide. So on a susceptible plant you may have a higher number of aphids you have an insecticide treatment it should decrease. If you move over to a resistant plant if you use an insecticide on that if that decrease in aphids after treating was the same as on the septal plants you call that an additive interaction or basically that the two treatments either insecticide or resistant plant they don't affect each other so they're compatible but they're not adding to each other at all. The other two the one I'll be focusing on primarily is synergistic interaction. So if you look at additive interaction those two lines are parallel and a synergistic interaction when you have a resistant plant that's treated with an insecticide those aphids are more susceptible so you'd actually have fewer aphids on that plant and that's the concept that we're hoping might be utilized in our research and another that we want to be a little bit worry about is antagonistic which basically means those aphids on the resistant plant might actually be less susceptible so we wanted to try to figure out what actually would happen because no one's looked into this field for soybean aphid before. So especially for a synergistic interaction there's been some other cases corn earworm rice plant hoppers where they're on the resistant plants and they're more susceptible and let's go through some of the potential outcomes for our actual research we're hoping with that synergistic interaction that there might be fewer insecticide applications if those aphids are more susceptible that might knock their populations down enough where someone might not have to spray more than once in a year or also thinking about insecticide efficacy for the organic growers since there's limited options there we might be able to take an insecticide that doesn't work that well and at least in general for aphids and if they become more susceptible that could work well for both aphid control but then also thinking about natural enemies where there might be less non-target effects because those natural enemies aren't affected by the resistant plant and think about this interaction that's another tool we like to say your integrated pest management or IPM toolbox trying to add more tools for farmers to use for whatever methods they're using. So moving to our actual study basically what we did was planted a susceptible line and a resistant line rag one was our gene that we use and we applied different insecticides one was Azera which is our organic proven insecticide has pyrethrum and neem in it as a mixture and then two conventional insecticides one was Laura's Ban the other was Warrior and then we also had our control plots which were no insecticide. So in 2013 we actually had relatively low populations of aphids they increased a little bit and then kind of stalled out the rest of summer at least in Rosemont where we had our sites so we actually had cages we put up as well besides monitoring just aphids in the open plots so we'd infest those cages right after a spray and see how aphid levels increased and that was also meant to keep natural enemies out so we could try to exclude any effects of natural enemies in the plant as well. 2014 we had higher aphid levels so we just sprayed at the economic threshold and monitored aphid populations afterwards and let me just open that up quick. So this shows our field data for that first year with two of the conventional insecticides clopyrifos lambicide halothrin and this is similar to those interaction graphs I showed you earlier we have no insecticide treatment in these white circles here and you can see both insecticides there were fewer aphids and both septal and rag one plants and then also because insecticide treatments but we also had those parallel lines or an additive interaction for clopyrifos but then the other insecticide we actually had that synergistic interaction except for azera that the organic-improved insecticide unfortunately we actually didn't see any effect we actually do the statistical tests on this the insecticide didn't work in either the susceptible or the rag one treatment so we included all these insecticides again for another year and the similar occurrences happened for azera at least where it didn't work again that year and that's something we're still trying to figure out what's going on with this organic insecticide that's not working out but for the other two conventional insecticides they actually switched their roles so one of them actually had a synergistic interaction and the other one was additive was the year before they switched their roles for that interaction type so there's something different going on each of those years so what we did after all this field data was to do lab bioassays and this is basically just taking a controlled dose of the insecticide trying to measure mortality and reproduction and we just play safe it's into a little cage on a leaf and use a clip cage to keep them on there and they'd be on that whole plant for two days being exposed to that insecticide and we use two two insecticides one was the conventional lambside halithrin the other was azera as the organic and azera is ongoing so I'm just going to present quick what happened with warrior or lambside halithrin warriors the trade name of that insecticide if anyone's interested in this case the lab assay actually didn't show the same effects that we found in the field that first year so we're using these lab bioassays try to figure out what the mechanism was that we found in the field but we're still working through what's going on but this is just a good example even though we didn't find that synergistic effect there's still fewer aphids in both your control and treated because of the insecticide so our main conclusion is we didn't find an antagonistic interaction which basically meant it didn't make the aphids more or sorry less susceptible to insecticides and that would be one concern that if people are out there spraying and it's they have to spray and a resistant plant that that might cause problems for resistance management of insecticides but our actual date on the conventional insecticide showing you those additive or synergistic interactions we aren't sure what was going on between those two years because the data was the results were different each year that could be because of weather one year was particularly hot and then another year we had a lot of rain afterwards and there are different chemistries so that might be something to think about for our future work or additional insecticides to test is thinking about different chemistries that they might have and yeah as I mentioned before Azera the organic insecticide wasn't effective and it was a little disappointing because we were hoping that we'd find an interaction there and have it to be a more viable option for organic growers so we're still looking into that area a little bit if there are other organic insecticides that might work out better and I said we have additional bio essays going in the lab it's winter right now so we'll see if we have any additional results there so for general outlook there are some insecticides where aphids are more susceptible to them on resistant plants so that key concept can move us into this next step thinking about okay what other insecticides could we find this in and could there be some benefits to that and that could be because it's safer for natural enemies that you might have better aphid control and not have to worry about non-target effects so much and also if there could be something available to organic growers for another control method and then also thinking about back to this IPM toolbox is you know there are many tools available right now they're scouting resistant plants and insecticides and then also the natural enemies which you'll hear about a little bit later so how do we include all these different control methods or evaluations and try to figure out what's the best way or most efficient use for farmers in different situations conventional or sterganic or different areas of the country as well so with that I'd just like to acknowledge Sarah again for funding the research and also Minnesota soybean growers and MGK for supporting my graduate student fellows or research as well and with that I'll take any questions people have so much so the question is it's whether differences between rag one and rag two and rag one is just a gene that will confer resistance so when you go to find your variety or someone's breeding they'll take a plant with that gene in it and if it has rag one in it then that offspring should have rag one as well and if that offspring has rag one in it it will be resistant to the aphid so is that clear yeah so for the rag one and rag yeah so for rag one and rag two you just take one plant that has rag one in it other with rag two read them together and that's it yeah so the question was what the mode of action is for rag one and I haven't seen enough information fully answer that the thinking is that there's well there's a mix part of it is antibiosis which means there's probably some chemical defense going on there but there's also anti-sinosis where they're repelling the aphids and it's mainly been characterizing that the aphids are being repelled or they're having lower population growth but why that's happening I haven't seen any information on that yet so that's probably ongoing research somewhere I'm sure so the question was if there's a yield drag on rag one and rag two I know for rag one at least there's not a yield drag I haven't seen examples for all the other rag genes and I can't say for sure on rag two I want to think there isn't a yield drag there but they've definitely tested rag one and there isn't a yield drag yeah so the question was if or what the availability is of rag one and rag two plants and there are rag one or just rag one varieties alone available that I've seen it's tougher to find them I think I was just looking through some seed catalogs and they had them but if you go further down south there's definitely the rag one plus rag two so I did have to check with your local seed provider