Spotted Lanternfly: Research Update
This presentation summarizes the current research projects.
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- [Julie] Good morning, my name's Dr. Julie Urban, and I'm a faculty member here in the Department of Entomology at Penn State University, and I'd like to talk with you today about the research that is being conducted on spotted lanternfly.
And before I begin, I want to mention, one thing that is probably apparent to any of you who are familiar with lanternfly is that it's kind of striking how little we know about this insect, and I just want to describe briefly why that's the case and give us a little bit of an historic context here.
I'm an evolutionary biologist who was trained, who specializes in planthoppers, so in the 14,000 species superfamily to which lanternfly belongs, and basically lanternfly is a really unusual beast even among the planthoppers.
We know that lanternfly feeds upon more than 70 different trees and plants, and that's highly unusual.
There are a number of planthoppers who are serious economic pests of cereal crops of all the major commodities, cereal commodities in the world, and we certainly know a great deal about their biology.
For example there are several planthoppers in a different family, in the family Delphacidae, that are major pests of rice, and when you get an outbreak of one of these rice hoppers we call them, that can knock down rice production by 80%.
And so, certainly these are economically important, there's a lots that's known about the science and biology of these insects even though they remain difficult to control.
But if you think about rice or corn or any of these other crops, they're produced in one year and they're harvested and that's it, and also these rice hoppers for example, they only feed on one or a small handful of plants.
Spotted lanternfly is really unusual in that it will feed on so many different plants, and many of these plants are trees, they're not, you know, grasses and whatnot that can be harvested in one year, so trying to determine the longterm effects of lanternfly impact on such a variety of long-lived trees is really an unusual situation.
And if we think of other insects that are sap feeders on long-lived trees, for example the hemlock woolly adelgid, and other adelgids are really the only ones that come to my mind, and those are highly limited in the number of hosts that they use.
And so this combination of lanternfly feeding on trees where the impact is going to be much more longer term, and that it feeds on so many different things is kind of why this is a unique situation, why we don't really know much about lanternfly biology.
And so, with that, some of the research that first began on lanternfly began when it was first detected in September 2014.
At that time, within two weeks, the United States Department of Agriculture pulled together a technical working group of scientists from around the world and even some folks from other countries, from China, and Korea, and we began meeting.
I was a member of that group, I wasn't at Penn State at the time, and we each began conferring and talking about the important aspects of research that needed to be conducted, and a variety of research projects were begun at that time.
And so with my work, I began looking at the genetics to determine the origin.
Other folks at USDA, other scientists started looking at lures.
Faculty here at Penn State started looking at insecticides that might be useful, and started looking at behavior, and folks at other institutions in forestry at USDA and in other universities began looking at predators and parasitoids of lanternfly.
And so that work was begun, but it was begun with a small, limited number of funds, and progress was made, but it was really last year when we saw lanternflies in the number that we saw them where it was really apparent to the researchers that we need to have a more unified approach to our research on spotted lanternfly and we needed to try to pursue multi-year funding, which we still have not yet gotten, in order to train students and bring in the best and the brightest postdocs to develop a longer term research approach to lanternfly rather than studies that are done with limited funding in one year or less.
And so along those lines, as I said, we still don't have that funding in place as lanternfly is still an emerging pest, but in the meantime, Pennsylvania Department of Agriculture and Penn State University have come forward with some funds to get us, to allow us to do immediate research to come up with immediate solutions.
And so that's largely what I want to talk with you about today, what are we doing to try to control lanternfly now and what are we doing to learn more about its biology to control it with other more, less chemical-based strategies and more longer term sustainable management strategies.
And so, in terms of insecticide efficacies, this is our frontline of defense with this pest.
We need to control the extreme numbers we're seeing particularly in vineyards and in orchards.
And so some of the research that folks at Penn State are doing, in particular Greg Crochett, down at our fruit research experimental station in Biglerville, he's conducting research in collaboration with Beekman Orchard which is in the quarantine zone, they were heavily hit last year with lanternfly, and again this year, and so they're testing various insecticides against egg cases.
And so certainly we're not saying that the way that we would control lanternfly populations would only be using ovicides, because you know, if these insects are laying their eggs 30 feet up into a tree, certainly spraying the egg cases is not what's viable, but in terms of considering egg cases being laid upon any variety of substrates including apple bins or containers used to transport grapes, certainly these would be the structures that we would be looking to treat with these insecticides to prevent lanternfly movement in those types of commercial interactions.
Also at the Penn State Berks campus, led by David Biddinger at Penn State and involving several of us, we're, we have 500 peach trees that we've used and we tested 20 insecticides against nymphal spotted lanternfly and then again as adults, and as of last week we began a study testing 10 of these most effective compounds against lanternfly on grapevines.
And so, from the peach tree data alone, we used some rates that were relevant to grapes and so from that, 10 compounds have been, well, now have the data to be labeled for use against spotted lanternfly, so that's very good.
We hope to add more with the grapevine study.
Certainly, lanternfly is not just hitting commercial vineyards and orchards.
We know that homeowners and green industry owners, we see it hitting ornamentals as well, and so with that, we have two sites where we have worked with where we have a series of maple trees that were all planted at the same time, and so a variety of compounds have been applied at different rates by the companies Rainbow and Arborjet, and so we're collecting data to scientifically evaluate those to come up with recommendations for some homeowners and the green industry.
Also, it didn't make it 'cause it just happened last week, Kelli Hoover here in our department has tested a variety of over-the-counter contact insecticides that are available to homeowners, and those will be, those data will make it into a new extension publication very shortly.
Also, in order to determine more scientifically sublethal rates and to understand exactly how much of an insecticide compound, exactly what it does to lanternfly, we need to perform this in controlled laboratory conditions and along those lines we have a collaborator, Tracy Leskey, who is a USDA scientist in West Virginia who just received permits to establish a colony of spotted lanternfly at Fort Detrick in their quarantine lab and so that will allow us to perform a variety of highly controlled lab studies on insecticides.
Other things that are again frontline of defense, a colleague, Miriam Cooperband who's a USDA scientist in Massachusetts, she's been testing how attractive various compounds are to lanternfly in order to determine a lure that might be useful in trying to trap them.
And so far, she's developed a lure that's the chemical compound methyl salicilate, and so she's testing those lures experimentally out in the field this year.
Also our outreach extension specialist for lanternfly here at the college, Heather Leach, working also with Tracy Leskey, they're testing these lures, this particular lure using a variety of traps, and they're doing this here in Pennsylvania and in Virginia where we know we have in Pennsylvania high lanternfly densities where they're testing their traps, and in Virginia, we have a population of lanternfly and there the densities are much, much lower, and so this will allow them to develop, figure out how effective the lure is and what trap design is best to use to monitor and detect lanternfly, particularly in low density areas where lanternfly might just be moving into a newly established area.
Also, as we're studying lanternfly, as I said before, we really don't understand a great deal of the basic biology of this insect.
We don't know what it's doing to the physiology of the plants it feeds upon.
And so we have one particular study, my PhD student who has some three-year-old grapevines planted in a vineyard, and we're introducing different numbers of spotted lanternfly and allowing them to feed, and we're caging the lanternfly on those plants, and we're also, with that, we're looking at then various aspects of the physiology of the grape plants to see how they respond to different levels of lanternfly feeding.
We're conducting some similar studies, they're not as far under way as the grape study, but we're doing that with ornamentals, again focusing primarily on maples.
And that's going on here at a quarantine greenhouse facility that we've received permits to rear lanternfly in.
Certainly a classic biocontrol is really important to try to find predators or parasitoids that can, you know, without using chemicals, that can help keep populations in check.
And so we have colleagues, Kim Hoelmer, and Julie Gould, who are USDA scientists, who've been traveling to Asia, primarily China, to find predators and parasitoids, which are wasps, that lay their eggs in the eggs of other insects, to see if there are natural parasitoids and predators of lanternfly in Asia.
When the other part of that, before you then would introduce such a parasitoid here safely in its non-native range, we would need to determine whether or not these insects are limited in their impact, only focusing on lanternfly, or if they are going to also try to lay their eggs into our native, non-target, in this case non-target planthoppers, and so colleagues at University of Delaware, Charles Bartlett, are examining the impact of any potential biocontrol agent on non-target insects.
And then also, there's been a search led by Ho Ping Liu, who's in Pennsylvania Bureau of Forestry, to determine if any native parasitoid who's currently here present in our area is using lanternfly egg cases to lay its eggs in.
And actually, he has found that there is a parasitoid, a parasitive wasp, that had been previously introduced about 20 years ago to control gypsy moth populations that's currently laying its eggs, it's parasitizing lanternfly eggs.
To date, based on numbers he obtained last year, this isn't occurring at a high rate, but this is continuing, he's continuing to monitor this in case, because that might actually increase over time which would be great news for us.
Also, there's research going on primarily from Tom Baker who's a distinguished scientist in entomology department here in Penn State, in order to look at the mating system of lanternflies.
And so we know that other insects such as the brown marmorated stink bug, they use pheromones or, you know, chemical attractants to attract mates, and that tends to be a really good lure, and so Tom has been looking to see if lanternflies produce any type of sex pheromone that we could use to attract them into traps.
And to date, he's found no evidence of any sex pheromone.
No planthoppers in fact are known to produce pheromones, and so this isn't really surprising for the planthopper folks among us.
Actually they use what we call substrate borne vibration, they actually call to each other through the plant, and so Tom, and then my doctoral student, is also looking at this type of non-pheromonal, or substrate borne communication, that's still in its earlier stages, but also Tom is continuing to look at dispersal behavior and seasonal changes in lanternfly.
It was rather surprising last year when we saw at this time of year, in September, what we called swarming behavior where they flew into areas in high numbers where they hadn't been feeding up to that point in the season, and we're interested here in determining what triggers those flights.
Is it a trade off in terms of sending energy away from reproduction or away from other processes to invest more in wing musculature to allow for greater dispersal?
Or are there other kind of developmental changes that are going on that underly this need to move?
Also to determine how this corresponds to senescence or the relative dormancy of the different trees that these insects are feeding upon.
As I mentioned, that some of my work started in looking at genetic markers to determine the origin of Pennsylvania, so these genetic markers, we call them microsatellites, but these are the same, these are highly variable regions of the genome, they're highly variable regions of DNA that vary among individuals in a population and so this is, these are the repetitive regions or highly variable regions of DNA that are used in humans for paternity testing, and so with that, some of these markers were originally developed by Korean scientists because spotted lanternfly was an invasive pest there that appeared in 2004, and they developed these microsatellite markers, and in using those, what I found, what I was able to determine is that Korea is not where our spotted lanternfly population came from.
If you look, just what these colors are supposed to show, relative colors, the green, blue, and red just show the relative amount of variation in these particular markers and the green, on the left under number one, is the amount of variation that we see in these particular markers in our Pennsylvania spotted lanternfly population, and those other numbers are lanternfly populations from Korea, two, three, and four, and then from Vietnam and China in the other sets, and what you can see is that our population doesn't match very well at all to the Korean populations.
It might match, we think it might be matching a bit to China, but what we see is that we need markers that are a lot more variable, and so we need better tools here and that's something that I'm working on in my lab.
Also, spotted lanternfly, because it feeds on sugary plant sap, it means it excretes sugary excrement, and we call that honeydew.
And this honeydew is a perfect substrate for black sooty mold to grow.
You can see in this picture, the black sooty mold is blackening a grape leaf.
It has the potential to block photosynthesis in the plants.
We haven't seen that to be too much of a problem in grapes because growers typically spray fungicide that keeps that at bay, but where we're seeing that is a problem is in understory plants in more natural forested areas or at the edges of natural areas where we have lanternfly in abundance.
The sooty mold growing on their honeydew will blacken the understory plants, and we're certainly concerned there about what that means for those understory plants which are often important food sources for wildlife like wild grapes and mulberry, but also we're worried and concerned about what this might mean for longer term nutrient cycling and plant regeneration in those natural areas, and so that's something we're looking at, and in my lab, what we want to do is to figure out exactly what is sooty mold, and so we're using DNA sequencing to characterize what it is that comprises sooty mold, is this the same, are these the same organisms that grow regardless of the substrate that it's growing upon?
And potentially figure out if there's any type of then antimicrobial compound that might be present in other communities not affected that we could use to control sooty mold growth.
Also with that, with microbial work, lanternflies are interesting creatures, and why I began studying them in the first place is that, like any of us, they certainly have a microbiome, you know, we often hear in the news microbiome literature, or microbiome studies, and this is certainly in our guts and our digestive tracts as in lanternflies.
They have a variety of microbial bacteria, bacterial agents that help them digest and whatnot and that's something that we're looking at, but kind of more importantly, lanternflies actually have organs that contain bacteria that have co-evolved with them over evolutionary time that feed them from the inside out and so that's something that my lab is looking at and potentially interested in if we can disrupt the transmission of these bacterial symbionts from parent to offspring, then that might be a highly specific way we could control lanternfly.
Also in terms of feeding behavior, one of the big questions that is important to study but very challenging to study, is trying to determine whether or not lanternfly requires tree of heaven or ailanthus altissima is the scientific name, to complete its lifecycle.
And so we do not know if it does.
Certainly it shows a very strong preference for tree of heaven, which is why control efforts aimed at lanternfly are focused on treating tree of heaven, removing tree of heaven and treating remaining tree of heaven trees, and that's certainly an effective way to kill high numbers of spotted lanternfly, but in order to determine whether or not it really requires it, requires someone to rear spotted lanternfly from eggs all the way through to adults, allowing the adults to mate, allowing the adults to lay eggs, having those eggs successfully overwinter because we only get one generation of lanternfly per year, and to date nobody's been able to successfully carry any populations of lanternfly through over a winter.
What we know is that some work done by Kelli Hoover here at Penn State, other work done by Miriam Cooperband in Massachusetts is that nymphs can develop from, in Miriam's case, from early instars through to adults on a variety of different hosts, on several different hosts other than tree of heaven, and Kelli has found that she's been able to get nymphs to develop into adults as well on, without tree of heaven, but to date no one has, these individuals have not made it and laid eggs.
We'll see, we still have this year to see if that can happen, but as such, it's going to be a bit challenging to really answer this tree of heaven requirement.
Also, some of the things that we're doing, we noticed that spotted lanternfly tend to show really high preferences for certain trees, not just certain species of trees, but in a row of say four silver maple all in one place, we tend to see one of those trees will attract very high numbers of lanternfly whereas the others don't, and so we're interested in trying to determine what it is that makes an attractive tree for a lanternfly.
And so, with some new equipment, we're measuring the flow of sap, or phloem flow in these trees, and also looking at other nutrients to try to determine what makes the tree attractive in terms of being able to rear spotted lanternfly.
We're doing a variety of other things, looking at the opportunities to try to rear them on artificial diets, because that might be helpful in getting a colony going, and also we're interested in determining as lanternfly feeds on trees, exactly what are they doing to the trees?
What are they doing physically as the penetrate the tree?
We see them exhibit competition for feeding sites, and so we're interested, are they doing anything to physically manipulate the tree?
Here we're also looking at the proteins in their salivary glands, again in order to see exactly at that entry level what is going on when lanternflies are feeding.
And so, I think that wraps up the research that, it's definitely not everything, 'cause there's new things coming onboard every day, but to give you a sense of some of the things that we're working on here at Penn State and with collaborators, and that other collaborators are working on, these are some of the immediate studies that are being conducted right now for spotted lanternfly and its control.
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