The Two-Spotted Cotton Leafhopper: An Urgent Conversation with Clemson’s Entomologists
Blooms and Beyond — Season 1, Episode 09
Host: Dr. Ping Yu Guests: Dr. Zee Ahmed, Assistant Professor of Turf and Ornamental Entomology, Clemson University; Dr. Tom Bilbo, Assistant Professor of Vegetable and Strawberry Entomology, Clemson University Producer: Rich Braman Duration: 55:18
Welcome to Blooms and Beyond
Ping Yu: Welcome to the Blooms and Beyond podcast, a podcast that uncovers plant history, culture, and management through the lens of science. I’m your host, Ping. How’s everyone doing today? I’m doing great because I have one of my dear colleagues and friend, Dr. Zee Ahmed, here with me today to talk about one of the most urgent topics in the green industry, two-spotted cotton leafhopper. Zee has been working on different pests for years, and we’re going to pick his brain today to address one of those most concerning issues.
A bonus for you guys today is besides Zee, we have also brought another colleague, Dr. Tom Bilbo, who has been dealing with this pest in vegetables, to give us additional perspective on this specific pest. So without further ado, I don’t want to steal any more spotlight from our speakers today. Let’s just jump right into it. Without further ado, here is my conversation with Dr. Zee and Tom. I hope you enjoy it.
Meet the Guests: Zee Ahmed and Tom Bilbo
Ping Yu: So hi, Zee and Tom. Welcome to the podcast. But first, let’s start off with the introduction. Can you tell us a little bit about who you are and what you do? Zee, do you want to go first?
Zee Ahmed: Thank you, Ping. I appreciate you inviting us to discuss this important topic. Hi, everyone. I’m Zee Ahmed. I am an assistant professor at Clemson University, and my lab technically works on turf and ornamental entomology-related issues. And overall, the focus which I have in my program is sustainable pest management. We do work on sustainable pest management and we want to help people control the pest in the turf and ornamental industry sustainably. And there are different schools of thoughts about sustainable pest management. The one which I believe and I want to do in my career, especially on this position, is to help growers apply control safely and at the same time with less cost. So that’s where I feel like sustainability is safe and cost-effective.
Ping Yu: Tom?
Tom Bilbo: Hey, Ping. I’m Tom Bilbo, Assistant Professor of Vegetable and Strawberry Entomology. I’m also at Clemson University. I’m at our Coastal Research and Education Center in Charleston, South Carolina. Most of my research is in biological control of insect pests, insecticide resistance, and improving insecticide use overall. And so this is an interesting insect because it crosses over into a variety of fields, you know, ornamentals, vegetables, field crops. So it’s an interesting problem for sure.
Growing Up with Nature
Ping Yu: So Tom, do you think you guys grew up as a nature kid or how did you first spark your interest in pests and plants? Or is this something just you never thought about getting into, but somehow end up in here?
Zee Ahmed: Well, I think I would say I was a nature person. I was an outdoor person. I still have very vivid memory of me collecting dragonflies during my primary school. That’s what I remember, earliest memory. So yes, I was a nerdy nature guy.
Ping Yu: What about you, Tom?
Tom Bilbo: Yeah, I grew up like in, you know, being big in the nature, but I didn’t — I wasn’t one of those kids that grew up playing with insects. I was afraid of spiders and I had my parents do a spider check in my room, you know, every night. But now I love spiders. But yeah, it really wasn’t until college — had a really good undergrad course with a great teacher, Tom Schultz, and then studied abroad and saw some amazing insects and just fell in love with entomology. Yeah, so that’s kind of how I came about it.
Academic Journeys
Ping Yu: And then did you get your — where did you get your degrees?
Tom Bilbo: My undergrad was at Denison University in Ohio and then PhD at Clemson University.
Ping Yu: What about you, Zee?
Zee Ahmed: I got my undergrad in entomology from Pakistan. About 7,000 miles away from here. So I have a very interesting journey to reach where I am now. Right after undergrad, I was looking for a scholarship and there was a cultural exchange scholarship between Pakistan and China. So I moved to China in Guangzhou, one of the third largest cities in China. And there’s a famous agriculture university, South China Agriculture University. Did my master’s there.
And right after my master’s, I was looking for a PhD scholarship. And that was a time when Commonwealth scholarship was announced and I applied for Commonwealth scholarship. I was asked to choose one Commonwealth country. So one of the Commonwealth countries and I decided to go to South Africa. I did my PhD from University of Pretoria, again, across the continent, went to different continent. I was so much energetic. I don’t know why I had that much energy that time.
So then I was looking for a postdoc. I was offered postdoc with the University of Florida. I was with the University of Florida for about four years. Then I was offered a job with the Florida Department of Agriculture and Consumer Services. I was there as an entomologist for four years. Then I moved to USDA for about four years. I was a research entomologist with USDA Fort Pierce facility, working on ornamental pests. I came to know my predecessor decided to leave this job. He jumped ship and I was so happy, but at the same time sad because my predecessor was very well known in turf and ornamental industry. So then I moved to Clemson University last year. And since then, I’m here and very excited to be part of the academic community again.
Ping Yu: Yeah, yeah. Well, don’t worry. Your predecessor is doing great, but you are going to do a great job too.
A Moment in Mandarin
Ping Yu: Speaking of that, do you speak any Chinese or Mandarin while you’re in China?
Zee Ahmed: I guess you have to learn to buy stuff, right? Otherwise, you have to… Like bargaining was something you have to do whenever you go out. So, “duōshao qián” was my first — even before “nǐ hǎo,” I learned “duōshao qián.” And I guess that’s something my senior told me that I have to learn that word whenever I go buy the stuff. I didn’t even know how to say numbers, but I knew how to say “duōshao qián.” And then we do a numbering on calculators.
Ping Yu: I’m talking about the price. Yeah, and “duōshao qián” is “how much.” If you ever watched the stand-up comedy with, oh gosh, Jimmy O. Yang, he had a special episode or special, Netflix special. Guess how much? That’s his mom’s catchphrase. I guess that’s an Asian thing.
But Tom, do you run into the same issue while you were studying abroad or with your exchange program?
Tom Bilbo: Having to speak other languages? No, I’m just, I’m a typical American. I studied abroad in Ecuador. Spanish? I attempt to speak some Spanish to get around and basics like that, but… No, I can’t. I can’t hold my own in a convo. I can read the newspaper a little bit.
How the Two-Spotted Cotton Leafhopper Was Discovered
Ping Yu: So how did you guys start to work on this pest issue or this pest? Because I think the whole thing, the two-spotted cotton leafhopper, started to draw attention. I don’t know about vegetable or cotton industry, but in green industry, I start to hear that a lot since earlier this year. And then all of a sudden it becomes such a big issue. But can you share a little bit about the background from your side of how you guys got interested and drew your attention to this pest?
Zee’s First Encounter
Zee Ahmed: Yeah, so I can go first. I was, first time I came to know about this from my colleague here, Dr. Francis Reay-Jones. He came to my office and told me that they are having a lot of issues with the cotton. And he brought actually a sample to me and we were taking pictures together for that pest. So that’s where I started thinking about it. And that was around early summer this year. I know I talked to my colleagues in Florida. One of my really best friend and colleague, Aimee Roda, I talked to her. She was previously working in USDA. Now she’s with the University of Florida. I talked to her briefly and then I started looking for it in Florida.
South Carolina, because my aim was to see if we have it here. Obviously, we knew it is on cotton for sure. And within just a week or something, we received a call from a grower at our farmer’s market. And she grows hibiscus and she sells hibiscus. And apparently, the hibiscus which she had in her backside of her outlet shop in a farmer’s market, there were over 100 hibiscus. And she wanted me to go and check them. And I took my students and went there without any effort. They were there.
We were not sure how long they were there and then we traced them back to the nursery. Again, I’m talking about those hibiscus which were being grown here and not those which were imported, and they were there and it didn’t take us much effort to find it. And that’s what I came to know about it and since then, all our efforts are trying to help reduce the population, because we know we still have growers who have a zero pest tolerance. So we’re trying to find a way to reduce it at a zero so they can sell their crops. That’s what was my first introduction with this pest.
Tom’s Encounter on the Vegetable Side
Ping Yu: What is — what’s the story behind the thing on the vegetable side, Tom?
Tom Bilbo: Yeah, really for us in South Carolina, it really came out of nowhere and it came fast. Didn’t — I hadn’t even heard about the insect until again, like Francis Reay-Jones and Jeremy Green, our colleagues here at Clemson working in cotton. They brought it up in like July; maybe I was like, yeah, I’ll keep a lookout for it. You know, only a couple of weeks passed before we started finding it. I mean, in the low country where I am, low country, South Carolina, it’s like every okra we look for, we found it on. And so we have a good agent down here, Zach Snipes. He went around and just, I mean, almost every single farm had it. And we’re like, wow, okay, this is — it’s not just here, but it’s everywhere. And we got to start getting a grip on it. So then all of our agents banded together and they started sampling a lot of the counties in South Carolina. And we started to understand that it was pretty widespread both throughout South Carolina and among cropping systems.
Timeline: When Did It Arrive?
Ping Yu: Do you guys happen to know when it is first reported in the United States? Is that an invasive pest or is it just native pest?
Zee Ahmed: So it was reported in 2024, if I remember correctly. Tom, you can correct me. But before that, it was reported in the Caribbean. Yeah. And then it was reported in Florida. And 2025, it’s now almost all in Southeastern states. I cannot say all, but most of Southeastern states has it. And it seems like it is here for some time based on the number of generations we are finding, based on the level of infestation.
Ping Yu: So, because I think one of the major concerns of this pest, at least for the green industry, is once it becomes a quarantine pest in any given state, it makes it even harder. It kind of worries people, especially growers, who have to deal with this pest. It’s kind of like the situation with thrips parvispinus back then in Florida. And people freak out because they have to control this pest. Otherwise, they cannot basically run their operation for days until they’re clear.
Biology and Identification
Ping Yu: But back to the point, can you give a little background, an introduction to our audience today who may not be familiar with what is the two-spotted cotton leafhopper? Can you share with us a little bit about the pest? Basic information on the biology side. What does it look like and what is their life cycle?
Life Cycle on Hibiscus
Zee Ahmed: I can go. So regarding the life cycle, which is I think so whenever we receive any invasive species, we are dependent on the life cycle study, the biology study, which came from the native region, right? And that can sometimes — that helps, but we still have to do our own studies. We are in the process to do life cycle study.
So first thing I would say right away — for this, it is really small. I’m talking about the adult, it’s less than five millimeters. So it’s really small. And the best thing about this is that it has two black spots on its posterior wings, both wings. So you can see those two spots. I’m talking about adult. Size is still small, but those two spots is the reason it has a name, two spots, cotton leafhopper.
So it lays egg and eggs, within six to nine days, they hatch in the summer because the study was conducted in the summer. And there are five nymphal instars. We observed based on our initial data that each instar lasted two to three days. This is something which is talking about on hibiscus. So in overall, we are noticing that egg to adult developmental period on hibiscus was about two to three weeks. This was study conducted — we are still doing this. We’re still doing this work, but this was done in September and October in the field cages.
So the nymph, they usually feed underside, allowing veins of the leaf. And overall, what we observed so far, adult lives about two weeks, about 13 to 14 days, male adult. And the females, they live a little longer than the male. Life cycle very heavily dependent on the temperature and host plants. We recently published a study in GrowerTalks, which is online, came in the December issue, and we provided a field guide for — with the very initial data about its diagnostics and its biology on hibiscus. So I would really recommend people to look at it.
Damage Symptoms: Hopper Burn
So a little bit about the damage symptoms. We are noticing that, as you have seen in literature, this hopper is associated with a very specific damage which is called hopper burn. And hibiscus, we found the burn was not as much as in cotton. Again, we had a light infestation when we got hibiscus. And when population was there for some time, we started finding a lot of yellowing and browning. And then we did find a wilting and curling of leaves. And again, the symptoms are yellowing, curling, wilting, and typically it is called hopper burn. And that’s on hibiscus. I think Tom maybe went ahead from vegetable side.
Tom Bilbo: You can find similar symptoms on the vegetable — yellowing of the leaves, curling of the leaves for sure. I guess just to add what you said, you noted they have the two spots make it characteristic. I think you were compiling a list — I don’t know if you published it yet — a list of possible lookalikes, but I think at least in the U.S., if you were looking for that, you know, leafhopper shape and then those — and then the spots is more or less indicative. You know what you have. And you’re like you said, it’s small, easy to miss. A lot of folks, I think, are seeing the damage before they’re ever seeing the insects.
Why Cotton Leafhopper Affects Hibiscus
Ping Yu: Yeah, just to clear one thing here for people who doesn’t know why cotton leafhopper is a big issue for hibiscus from the plant perspective. Cotton and hibiscus are from the same family. So that’s why the name is cotton leafhopper, but it does cause a lot of damage for a lot of ornamental plants that share some similar characteristics with the family.
Host Range: Malvaceae, Solanaceae, and Beyond
Speaking of that, do you guys know what is the host range for this pest? I know it’s wild, but can you give us a couple examples from both ornamental and the vegetable side?
Zee Ahmed: As I mildly said, it has a broad host range. So, there’s no doubt it’s a polyphagous pest. It’s going to hit a lot of host plants. But I want to re-emphasize on the Malvaceae family, which has cotton, hibiscus, okra. Tom can also confirm that. It has a special preference for that. Yes, we know that family contain a lot of economically important crops, but then there is another family which is Solanaceae, which has eggplants and some other important crops. It does feed on that too. So yes, polyphagous. Malvaceae and Solanaceae, these are important families where it can feed. And it might surprise us with some host plants which we are not familiar with.
Most of the literature on this pest from the Old World is actually from cotton growing regions because that’s the main crop in the native region of this pest. So there are not many studies that were done on broader host range because people were so busy — because it was a huge problem in cotton, so they were so busy dealing with the cotton and cotton is an important crop in its native region, they’re not much done about exact host list about this pest. So we’re going to learn about it in the next few years.
Tom Bilbo: Okra and eggplant are known to be at greatest risk. Okra really is getting hammered. For us, that seems to be highly preferred and highly susceptible. I’ve been to farms that have both eggplant and okra — have always been a lot worse. On okra, the numbers, it can really just get out of control. And so a lot of our okra growers are having issues with it. Left unmanaged, it’s just completely killing plants.
Okra, which is — I mean, okra is a hardy vegetable. It’s not known for being attacked by as many pests as some of these other vegetables are, but this is definitely a problem. And it can get into these fields really quickly. I planted a small little stand of okra here in the fall. And these okra were barely out of the ground and they were already covered by leafhoppers. And it’s like, where did they come from? They just, they found the okra really quickly and they were killing that plant pretty quickly. So, but it’s such a new pest. We have so much to learn about it. But yeah, the wide host range is of serious concern.
Hibiscus as a Dispersal Driver
Ping Yu: Yeah, because I would assume this pest, similar to other invasive pests as well, they would have a wide host range for attacking a lot of plants, but apparently they have their favorite and preferences. Am I getting right at this stage with all the knowledge that we know about this pest from the vegetable side and hibiscus — from the, well, okra and cotton from the vegetable side. And I don’t know if cotton is categorized as vegetable.
Zee Ahmed: You might offend cotton people.
Ping Yu: Oh, sorry. Let me rephrase. So from the cotton commodity group, the cotton, and from the vegetable, okra, from the green industry, from the ornamental side, it’ll be hibiscus. Those three are the most susceptible plants as of now with our knowledge about this plant. Is that right?
Zee Ahmed: So, yes, for sure. For vegetable and cotton, what you mentioned is true. And for hibiscus, it’s also true. But I want to put a disclaimer here. For hibiscus, the critical part is so far is what we are learning is hibiscus might be the driver to spread this because people buy hibiscus, they move hibiscus, they take them to landscape and then they take them closer to the field crop area, vegetable area. One of the major concerns regarding the hibiscus is it might play a very crucial role in its dispersal. We are at early stage. This is still a pest of limited distribution. Yes, hibiscus, it is a pest of hibiscus, but why it is crucial to learn more about hibiscus at this stage — because that might play a role in how quickly it’s going to spread and how we can mitigate its spread if we can control hibiscus, control it on hibiscus faster.
Ping Yu: Okay, and I could extend our knowledge a little bit by saying this pest might be in the cotton or in the okra and then spread or jumped into the hibiscus plant nearby. Would that be a possible alternative pathway for the distribution of this as well? Or it’s vice versa?
Zee Ahmed: No, I didn’t mean to say — I want to correct myself to make sure that I said the right statement. So I’m not saying hibiscus started the spread, but I’m just saying hibiscus move around faster as compared to — we’re not going to move okra from one house to another house, right? We’re not going to move it.
Ping Yu: Yeah, yeah, you’re right.
Zee Ahmed: So I didn’t mean to say that it’s coming from hibiscus, but I’m just saying hibiscus can be a plant which can move it around. Yes, it could be coming from hibiscus and then you move hibiscus from one area to another area. It could be coming from cotton to hibiscus and then you move hibiscus. Because cotton and okra will most probably not going to move around. Hibiscus is going to be move around. It’s going to dry. But it also could be any field area. Cotton, okra, hibiscus.
Ping Yu: Yeah, yeah, yeah, yeah. I get your point. I’m just, you know, depending on the nature of me being in the green industry. But I know what you’re saying because of the distribution of ornamental plants that might be redistributing the pest to other areas because of the plant movement or the trade.
Scouting and Detection in the Field
Ping Yu: But can you tell us a little bit about how growers can identify this pest in the field and how do they know if they have a pest issue?
Scouting Hibiscus
Zee Ahmed: I think for vegetable and cotton, infestation, again, I think I will let Tom say about vegetable. In general, for hibiscus, population doesn’t grow. This is, again, we just published an article in GrowerTalks, and we observed the biology on hibiscus is relatively slower as compared to what is published on cotton and okra. So population at hibiscus may not grow as fast as on other plants. That’s based on our very initial data. We are still in the process.
And then, so it means in hibiscus, you will be finding population low and the field guide which we provided in that article, it starts with learning about its size. So first thing you have to understand how big it is, right? Or technically I should say how small it is. And then second thing you wanna learn about its symptoms, damage symptoms. But the infestation at early stage, you may — the damage symptoms may not appear. So that’s how we started scouting in the landscape and there were successful incidents where we found it. We started flipping the hibiscus leaf starting from the middle to going upward.
And when you flip the leaf, you will see close to the midrib, you will see the tiny — I’m talking about immature one — because adults, they hop, it’s hopper, right? If you’re going to flip the leaf, they’re going to hop from one leaf to another leaf. So you’re most probably not going to easily see adult in the start, unless you train your eyes — will take some time for that. But you flip the leaf and they are immature, you will notice that they are like a tiny light yellowish thingy which will be less than two to three, between one to three millimeters in size. They will move in a very funny way.
The Hidden Egg Problem
And that’s one way — you’re not going to see eggs. So here another thing which I want to emphasize here, because they lay eggs inside the leaf. So, eggs are not visible, outside eggs are not very visible. And we may be unknowingly, because we see there is no immature or adult, but eggs might — since eggs we cannot see, we might be unknowingly skipping its scouting. So we need a regular scouting. Because eggs hatch, say, between seven to six days — six to seven days, or six, actually in our case, you know, hibiscus we found six to nine days. So you have to scout regularly because once eggs are hatching, you will see immature, but you will not be able to see eggs. So I would refer every listener to check out our field guide in GrowerTalks. We elaborated this description, diagnostic description.
Ping Yu: We focused on hibiscus in that guide. Have anything to add, Tom?
Scouting Vegetables
Tom Bilbo: Yeah, just that at the time being, we’re still working out sampling plans and all that, but you’ll just need to get out looking at plans, trying to find adults, find immatures. My guess is we’re probably going to see them at the edges of fields first in the sense of, you know, vegetable and cotton fields and all that. But again, we don’t have — I don’t think we have the transect sampling data yet.
Sticky Cards as a Monitoring Tool
Conducted yet so a lot that we’ll need to do, but yeah, I’ll say let me say something about sticky cards because we — I didn’t have any dedicated projects this past fall but we incidentally kept finding them in different trials we had. And so one of my PhD students, Sabina Parajuli, she had a zucchini trial and it had moderate infestations with two-spotted cotton leafhoppers. So, okay, so zucchini, that’s one we haven’t talked about yet. That’s a cucurbit crop. Why is it — it wasn’t expected to see so many of them there.
But from what we’ve seen here and from what our agents have said around the state is that a lot of people are seeing these show up in cucurbits. We don’t believe that they’re a pest at this point, but it’s just yet another host, another reservoir for them to exist in. So we had a zucchini trial and we had a lot of yellow sticky cards out there and the sticky cards caught a lot of two-spotted cotton leafhoppers. And I just analyzed that data and the sticky card counts have a pretty strong correlation with the plant counts. So at least in the case of zucchini, the sticky cards are reflecting what we’re seeing on the leaves. And so maybe an important monitoring tool and easier because this is such a small insect. You know, you don’t have to be there turning around leaves and looking around plants and choosing the right leaf and all that stuff. So the sticky cards look like they’re probably going to be a good monitoring tool. But again, we’ll want to hammer that out for specific crops and to see what the sticky cards actually tell us. But, you know, you could probably stick them up at the edge of the fields and I have a sense that they would give you an early detection.
Hand Lenses and Practical Tools
Ping Yu: I’m glad you mentioned the sticky card because I was thinking while you guys are talking about the characteristics of this pest and being so small, now can growers effectively detect them or monitor them at an early stage? Zee, do you know if anything has been done with the sticky card on the ornamental side? Or is this something that we need to look into down the road?
Zee Ahmed: I have not seen any data outside at this stage. I’m sure there are folks, some of my colleagues, they are trying to work on it. We did a visual count during our trial, but yes, I would also try to see down the road if we can use potentially to detect them at early stage, especially in a nursery setting.
Ping Yu: Yeah, because I think that would be an essential step for growers to early detect and have a good scouting program for this pest specifically. But other than sticky cards, are there any handy tools that growers can use to help them identify for their scouting, like such as the handy lens or the hand lens, things like that?
Zee Ahmed: At early infestation, a lens would be very helpful because there will be immatures and eggs will be hatching and they’ll be first, second, and early instars. So they are really small. And yes, lens will be really helpful. And I would suggest 10 to 30x lens, that would be very helpful. But once the infestation is established and it’s going to be heavy infestation, as I’ve seen in some vegetable fields, when infestation is heavy, you will see them right away.
Tom Bilbo: Yeah, they’re small and so they can be hard to find, but they’re bigger than — for us that work with thrips and mites, which can be even a lot smaller. And once you know what to look for and once you’ve been trained or you know what to look for with those spots and you have a hand lens to help you confirm, it’s not the most difficult insect to kind of look for and ID, but it takes — you know, you got to kind of know what you’re looking for.
Step-by-Step Field Identification
Ping Yu: Can you give us like a very clear and simple ways for growers to identify in the field? Like, for instance, you guys briefly mentioned about the characteristics of this pest, the two spots and we need to identify. Flip the leaves upside and to look for — can you give us like a very short, sweet way for growers to go look for when, where, what to look for in that regard so that they can have a very clear way to more accurately look for or identify this pest?
Zee Ahmed: Do you want to go first? First thing I would do — symptoms observation. If I walk into a hibiscus nursery or hibiscus production area, I would start looking for symptoms. Symptoms, because if there are symptoms, that’s probably one thing which I want to observe. Especially as I mentioned earlier, the hopper burn symptoms — yellowing, wilting, curling, all those symptoms which generally appear on hibiscus when they have pests. That’s a very general symptom for most pests. We want to help growers to be trained for that.
That’s where I think they have to — if I would be a grower, I would, or if I would be somebody who wants to scout, I would first equip myself with the available material. Here, one of them, I, as I mentioned earlier, field guide, which is, which we recently published, have that material with you. That I will do second thing. And then read that material carefully before you start scouting. And then at early stage, as I mentioned, if there are only eggs, you’re not going to see them. But then if you come back after, say, a week or something — a week, at least a week — not at least, at maximum week. So you should have come within the week and then check again. And if those eggs have hatched, you will see tiny light yellowish things on the underside of the leaf along the midrib. And they move very funny way. So they move from left and right for some reason. Observing them, make sure you should equip yourself with the available material and then go in the field knowing that you may not find it right away. But if you keep regular scouting within the seven days of previous scouting, if they are eggs, if they are hatched, you will find immatures moving on the underside of the leaf along the midrib.
Tom Bilbo: Yeah, the only thing I would add is, and this is my kind of general advice for scouting vegetable fields in general is, if you have symptoms, if you know what you’re looking for with the symptoms, then you can walk around and you can look for — if you have a sharp eye for those symptoms, you can cover a lot more ground that way looking when you’re not stopping and turning over leaves. You can cover a lot more area by going around and keeping a close eye for symptoms. And then when you see any kind of yellowing or maybe curled leaves, then you can start turning over leaves.
Or you can do it in a more controlled way where you are going to say, I’m going to do a transect across this field. Make and try to look at the borders and the interior, turning over leaves every 10 plants or, you know, how big the field is. But make sure to, especially until we know exactly the best places to look on each of these different host plants, is look at different plants. Don’t just look at the oldest ones. Don’t just look at the newest ones. But yeah, make sure you’re kind of looking at the whole plant because you may see them on some leaves and not others. So, yeah, that’s what I would do.
Where on the Plant: Eggs vs. Nymphs vs. Adults
Ping Yu: So basically right now, we don’t even know if this pest specifically prefers the new leaves or the older leaves or anything in between. Do you have any information on that?
Tom Bilbo: You can see a lot of the — you know, when they’re laying, like a lot of insects are laying eggs on leaves. They’ll lay the eggs, they may lay them on the newer leaves, and then by the time you start to see a lot of nymphs, those end up being, you know, maybe further down the plant or depending on the plant. So you may see a lot more nymphs on older middle-aged leaves, and you may see more adults laying eggs on newer leaves.
Ping Yu: So basically, it’s — it’ll attack the whole plant with their different life stage.
Management Strategies
Cultural Practices: What We Know So Far
Ping Yu: But are there any available cultural practices that could potentially help reduce the pressure of the leafhopper?
Zee Ahmed: I would say in a nursery setting, when inspect the plant, when plants are coming from outside for sure, anything coming out from outside has to be inspected, especially if it’s hibiscus. And I would also add here again, you cannot control eggs, right? Eggs are there and you don’t know if eggs are there because they are in the leaf. And so that makes it a little more challenging to suggest what to do when we cannot even see if the pest is there. So I would, at this stage, say scouting, scouting, and scouting. Inspecting material which is coming inside.
At this stage. We are hopeful we will have some data in the future about different varieties. And so we can say this variety is less susceptible as compared to other ones. There are some variety differences in other studies, so that would be helpful in the future. Again, not much to say. We are still learning about this pest. I’m talking about just the ornamental nursery production side. I wish I could say more about it, yeah, about cultural practices.
Ping Yu: What about from the vegetable side, Tom?
Tom Bilbo: By being — we don’t have anything concrete. We — there was a lot of ideas, you know, I think we’ll know a lot more after next field season when we actually had a chance to do things, but in general, like a lot of pests, you want to conserve natural enemies. We — that we don’t have a lot of good biocontrol studies done for this insect, especially in the U.S. But there was a lot of — there was a lot of predators hanging around these plants, you know, lady beetles and some others. And so they were probably eating some of these. So it’s always good practice to try to conserve those beneficial predators and parasitoids. And the easiest way to do that is to not spray broad-spectrum insecticides.
So, and I believe from the insecticide trial that’s been done, say the pyrethroids are a classic case of broad spectrum known for killing natural enemies. I don’t generally think they’re looking to be that effective anyways compared to other products, other modes of action, but avoiding the broad spectrum use, try to conserve natural enemies, let them help you as much as they can and hopefully we’ll develop more targeted bio-control strategies. But we have a lot to learn.
Mulch, Cover Crops, and Horticultural Practices
Ping Yu: I think that’s — well, that’s job security we’re talking about right now with all those things with this pest. But in general, I think, well, in the vegetable side, I guess there’s not so many to do, especially with the plants are in the ground — we can move. But for nursery settings, most of the plants are in containers. We can move them around. I don’t know if we have enough data yet to see if any of the spacing or mulching or pruning might be some ways to potentially reduce the pressure of the pest in general because we have seen some similar trends on other pests. So they might potentially provide additional ways for managing this pest. But again, we don’t have solid data yet.
Tom Bilbo: There’s a lot that we may be able to leverage — disrupting their ability to find fields or maybe plants and nurseries or something like that, you know, different kinds of mulches, reflective mulches. It’s very preliminary, but my student, you know, in that zucchini trial, two of the main treatments were those that had a lot of habitat complexity due to cover crop residue surrounding the plants. Those had less leafhoppers than those that were just bare ground. And so if that repeats next year and we see significantly reduced numbers in those cover crop habitat treatments, we try to get out why that is. Is it disrupting their preference for those plants or is it increasing biocontrol or some other mechanism? But a lot of folks are going to be doing a lot of research on this in the next year. Some promising areas, promising angles to attack this pest from.
Ping Yu: Yeah, because the reason why I asked about this is because we found a pretty interesting results from one of the ongoing works that we’re doing. My student who was working on thrips parvispinus, and she’s looking at different horticultural practices to manage this pest. And one of the ongoing trial that she did with the mulch trial, she did find effective way of using mulch to reduce the population of the pest. So I’m relating to the new pest because, well, it’s a different pest, but there are certain, like the concept would relate. So I was thinking maybe down the road, if we could do some trials on that, from that angle, we could potentially develop some effective ways from like the horticultural practices or cultural practices to better manage this pest. Yeah.
Chemical Control: The Hibiscus Insecticide Trial
Ping Yu: So, Zee, I know that you mentioned a lot about the GrowerTalks field guide. And can you elaborate and talk to us a little bit more about the hibiscus trial that you did and just share some of the results with our listeners today?
Zee Ahmed: So we just finished it, four weeks count, and we are in the process to analyze that. The work which we brought online as soon as we could in GrowerTalks, because that was in high demand — they needed something at this stage so they can — especially talking about growers, they needed something so they have some information. So we used six treatments based on IRAC groups, different mode of action, including contact, translaminar, systemic material, and the idea was to see if we can find groups which are effective and can be rotated.
The results are for 14 days, they are a treatment. So the data after treatment for 14 days is available in that GrowerTalks article, but we are in the process to finish the final version for whole research. So if I have to summarize that, we think there is a way to control it. It’s not — it’s not — sky is not falling. We can control this pest based on our trial. And we did mention about the effective treatments in that trial.
Matching Treatments to Life Stages
The thing which I want to emphasize here is matching the treatment based on the life stages. That’s something is very important. We should not be expecting that all treatments or all chemicals you’re going to use will control all life stages. So that’s something I want to emphasize. And as our translaminars — we think and systemic, they performed better against nymphs which are feeding. So they’re a really good result. I would suggest people to look at that data in that GrowerTalks article. And we were really hopeful that we can knock the population down at good level based on the products which are available.
Ping Yu: I will make sure to add the link to the show notes so people can click on that and look for more information on that. But you mentioned a key point here that the life stage of the leafhopper is critical for controlling this pest. Which life cycle or which stage of this pest is the nymph phase or adult phase most susceptible? Or if I put that other way, is the stage that people would target when applying any of the treatments?
Zee Ahmed: So this is what we did on hibiscus. So story can be different when you’re dealing with row crops. So we noticed that we can knock down adult with most of product. We were excited to see that. So when it comes to immature, again, I want to re-emphasize, we’re talking about here ornamentals. And ornamentals, we want to make sure growers can sell it without the pest on it. So we have a small window to control it and make sure we can sell it without, because we know consumers have zero tolerance for pest.
And so we wanted to have the products which we used — there are different mode of action and susceptibility obviously in general, if you talk about insects, immatures are more susceptible. They usually stay on the leaf, they don’t really go far. And in this case, adult hops — move from one place to another place and their dispersibility is more than immatures. But then we’re talking about growers where we want them to control all life stages so they can sell plants without pests. So we’re targeting all life stages.
We want to target adults, we want to target immature. We have our trial basically saying that if there are more immatures, then you have this product which you should apply. And if there are more adults, you should integrate this product with that to knock them down. And then you have to follow up spray too and follow up scouting as well. Because if I am doing spray today and I knock the population down and there are eggs which are there today, I’m not going to kill them. And they’re going to hatch. So, in that kind of scenario, we need a translaminar and systemic action. If eggs are hatching next week, seven days or 10 days from now on, they will not feed or if they feed, they will get the lethal dose in their body so we can have an effective result. If we strategize it, it can be controlled based on our results at this stage on hibiscus in ornamental settings.
Cross-Disciplinary Insights: Ornamental vs. Vegetable Approaches
Zee Ahmed: Can I ask Tom because I want to see if he can add on. If we are using a translaminar in ornamental settings, would you suggest translaminar, systemic and vegetable as well?
Tom Bilbo: There’s a lot of benefits from a pest management standpoint, yes, to translaminar and systemic because it can help you gain access to parts of the plant that can be difficult to reach. So now depending on the crop, you know, some crops you got to be — you want — you got to be extra careful about pollinators and all that. And but yeah, generally, yeah, the translaminars and systemics can help you out a lot by kind of getting, you know, the product can kind of get into those nooks and crannies better. So for a pest that’s going to be on the underside of the leaves, then you got to get good penetration of the spray and the canopy.
Ping Yu: Oh, I was asking, so from the vegetable side, do we, for the growers also need to target all stages of the pest when they apply?
Tom Bilbo: Yeah, I mean, like Zee said, nymphs are always more susceptible. If you can get adults, that’d be great. What it seems like, if it’s anything — if next year is anything like this year, they’re going to be everywhere. And if you’re growing something like okra, that’s highly susceptible, you’re going to have pest issues at some point.
So again, I’m really curious what’s going to happen with the overwintering this year and what we see next year. So we’ll keep a close eye on things throughout the year when the problems really emerge. But yeah, but if it’s anything like this year, you’re like guaranteed to have problems if you’re an okra grower in the lower half of the state. So it’s just a matter of when they’re going to be there. And you want to — if you’re basing it off of this year, then the numbers are going to get very severe. And so you want to manage them before it’s a total outbreak situation. So you got to get out in fields at least once a week. And when you start to see populations establish and build, then you got to know what you’re going to put out there. And you should probably have multiple — like have your rotation lined up from the products that we do know have some efficacy.
IPM Gaps: What’s Still Missing
Ping Yu: Are there any other steps or practices that growers need to incorporate for what they have for other pests into their IPM program?
Zee Ahmed: At this stage, we have knowledge based on what has been done in other parts of the world. And we have chemical control options which people used in other parts of the world. The thing which you are lacking is biological control. We don’t have much information about the biological control. As you already asked us about the culture control option, we have a culture control option based on common sense, based on the knowledge which we got from other pests. But specific to this pest, we still don’t know. Cropping season, planting time, and varieties which are resistant, less susceptible. And then the products which can be rotated, in the way that we can use them across three disciplines, across three crops — cotton, vegetable, and hibiscus — because the availability of products, what we will have, we can use. There’s a lot to learn about this pest at this stage. So, again, answer would be we don’t know much.
Ping Yu: Yeah.
Future Plans: Building a Collaborative Response
Ping Yu: I guess that brings to my next question. What is your plan — what is your next excitement for this pest in relating to your research side and extension side?
Coordinating Within South Carolina
Zee Ahmed: So far in South Carolina, we are collaborating very closely. Tom, he’s working on the vegetable side. I am working on the ornamental side. We have Dr. Francis Reay-Jones, Dr. Jeremy Green, they both are working on the cotton side. So our target is we first coordinate efforts. That’s our first aim, next step. We want to coordinate within this state.
A Southeast Working Group
Second step is that we also in the process to make a working group across different states in Southeast. We have already applied and Ping and Tom, you guys are part of that group. We want to have our coordinated efforts. I’m talking about a bigger picture at this stage. So we want to make sure what I am doing in South Carolina, as my colleagues are doing Florida and some colleagues are doing Georgia. We coordinate this all very well that we can plan this as a collective and collaboratively. That’s our bigger, bigger plan. And we’re really hoping that we can establish this working group. This will tremendously help to mitigate the pest dispersal, will help our growers. And we’re producing an extension-based article as well. I will publish in GrowerTalks. And a lot of material is coming through the website, social media, helping people, making sure people are aware.
Lab Bioassays and Deeper Research
And we are in the process to do a lab bioassay in my lab to see the efficacy, maybe at a deeper level. We just finished the plant bioassay. So these two projects at this time, we’re doing in my lab in an ornamental setting. And again, my focus is to make sure we have a coordinated effort. That’s something we need for almost all invasive species. And I’m hoping we will be successful in that.
Tom’s Vision for the Working Group
Tom Bilbo: Sure. Yeah, the working group will be great because having the collaboration — that’s the only way we can as quickly as possible generate a variety of recommendations. So yeah. Not every one of us can do everything. So having different people work on different things, we can quickly come up with a list of — we’ll know that, hey, these eight insecticides are going to be your bets to choose from. These are better early season. These are better late season. Maybe if we get some like the mulch work, like, oh, maybe reflective mulches or white mulches or black mulches tend to be more or less susceptible. These cultivars seem to be more or less susceptible. So we’ll hopefully start to piece together as much helpful information as possible.
And then of course we need to get that information out there. So making sure growers are aware of this pest and knowing what to look for so that they can manage it and so that they’re doing it the right way. And in the short term, that’s coming up with curative solutions like insecticides and making sure that they know what the pest is and they’re applying what we know to be effective and not going out there wasting money and causing undue damage by spraying the wrong product for the wrong pest or whatnot.
This fall, a lot of people didn’t realize what the problem was until one of our agents would get out there and be like, you have the new invasive. It’s here. That’s what’s causing it. It’s not aphids, it’s not whiteflies. So with the specialists and the county agents and taking a collaborative effort, getting the word out there, it’s going to be important. But I think, yeah, I’m feeling optimistic that we can come up with some good approaches pretty soon.
Ping Yu: I think working as a team can really make a difference — move fast and can piece together with the puzzle faster.
Thanks and Closing
Ping Yu: And thank you both Tom and Zee for taking time out of your busy schedule to talk with us and providing all those insightful information to our audience today. And thank you for all the work that you’re doing to help our growers and our stakeholders out there. So thank you.
Zee Ahmed: Thank you for inviting us. And I really want to say here that the efforts you’re doing are going to have so much impact because this kind of information needs to be spread faster and the way you are doing it. This is the new way and people are listening to it. And thank you again for inviting us.
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