Can Lanternflies’ Excretions Be Used To Quell Their Spread?

JOHN DANKOSKY: Now some research that might mean some hope in the fight against the invasive spotted lanternfly. We’ve talked about them before– the very pretty but very hungry insects that are spreading rapidly in the eastern US. And that has ecologists and farmers worried. This week, in the journal Frontiers in Insect Science, researchers from the USDA report that they may have found a clue to attracting the spotted lanternfly– chemicals secreted by the insect as part of a sugary goo called honeydew.

Joining me now is one of the authors of that report, Dr. Miriam Cooperband of the United States Department of Agriculture Animal and Plant Health Inspection Service, Plant Protection and Quarantine Division. Welcome to Science Friday. Thanks so much for joining us.

MIRIAM COOPERBAND: Thank you for having me.

JOHN DANKOSKY: So for those who maybe haven’t been up close and personal with a lot of lanternflies, there’s this gooey stuff left behind. What exactly is honeydew?

MIRIAM COOPERBAND: Basically, the spotted lanternflies feed on the plant phloem. They have piercing sucking mouthparts. They penetrate the plant with them, and they drink the juices out of the plant. But those juices, in addition to having some nutrients, they’re mostly sugar and water. And so spotted lanternflies filter out the nutrients and keep those, and then they excrete this sugary water substance that’s very sticky and gooey. And that excretion is called honeydew.

JOHN DANKOSKY: So you look at these chemicals that are in the honeydew, and what exactly did you find?

MIRIAM COOPERBAND: Well, we collected honeydew from male spotted lanternflies and from female spotted lanternflies. And we brought that honeydew back to the laboratory, and we looked at it to see what the chemical makeup of it is. And we also tested the honeydew in bioassays to see how the male and female spotted lanternflies respond to it. We gave them a choice, and they could respond to either the odor from the honeydew or to a control.

And what we found was the male spotted lanternflies had a significant preference for male honeydew, and females did not. And then, the male and female spotted lanternflies did not have a strong response to female honeydew but a very weak response.

JOHN DANKOSKY: So that seems a bit counterintuitive. Wouldn’t it make more sense if the male honeydew attracted females and vice versa?

MIRIAM COOPERBAND: Yes, it is a little counterintuitive. We were not expecting these results. But when we think about the ecology and the behavior of the spotted lanternfly in the field, it started to make a little more sense. What we see in the field, most of the time you see a 50-50 ratio of males and females. But then, for about two weeks before they mate, you can find trees that are mostly females and then other trees that have mostly males on them.

So for some reason– and we don’t understand this yet– the males and females separate before they mate, and then they come back together again when mating starts. This honeydew discovery that males are attracted to male odors from honeydew may help explain how they’re doing that. But it doesn’t explain why they’re doing that.

JOHN DANKOSKY: So explain, how strong an attraction is this? I mean, is it like attracting a bug to say, well, maybe I’ll go this direction or that direction? Or is it a very, very strong attraction that basically says, I need to be wherever that smell is?

MIRIAM COOPERBAND: Well, that’s a really good question. And that’s, of course, what we would hope because we want to find an attractant that we can turn into a tool to use as a lure. So we hope that we’re finding something like that. But this is in a laboratory setting, and so they have two choices.

Once we figure out what those compounds that are attracting them, we can go and try to develop a lure out of those compounds and bring it to the field and test it in the field. And that’s the tricky part because often you find attractants in the laboratory, but making them attractive in the field when there are so many other variables and so many other attractive things out there, that’s the tricky part.

JOHN DANKOSKY: So what makes that so tricky? I mean, give us a sense of those other variables that make it difficult to replicate something in the laboratory that might not work in the field.

MIRIAM COOPERBAND: So there might be multiple modes of communication. They may not only use honeydew. They may use other chemicals that are produced by their bodies. They may use substrate vibrations, which they detect through their legs when they’re standing on the same surface, and they can send signals that way. So there are multiple ways that they could communicate with each other. And this might just be a part of that whole big picture.

JOHN DANKOSKY: So as you suggested before, this might explain one of the really unusual phenomenons that we see with these spotted lanternflies, which is you’ll see one tree that’s just covered with thousands of them and another tree very close by that has none.

MIRIAM COOPERBAND: Yes. And again, we don’t know how they do that yet or why, how they aggregate in that way, what signals they’re using. This is just the tip of the iceberg. We’re just now discovering some of those signals. And I’m sure we’re going to be discovering many more as we keep working on this problem.

JOHN DANKOSKY: I have to ask you– is this one of the most confounding projects you’ve ever worked on? Everything I’ve learned about the spotted lanternfly, everyone I’ve talked to as they try to track it across the United States and keep it out of wine fields, for instance– everyone seems to be perplexed by this thing. Are you?

MIRIAM COOPERBAND: Absolutely. The spotted lanternfly is very enigmatic. We scratch our heads a lot when we find new things. The first few years we started studying it– lots of head scratchers. But as we started putting these pieces of the puzzle together and started seeing, well, they behave this way under these circumstances, and so forth, it is starting to make more sense and come together. So we’re learning a lot, and we’ve come a long way from where we were when they first were discovered here.

JOHN DANKOSKY: Well, good luck to you as you continue to travel down this honeydew path. I really appreciate your time.

MIRIAM COOPERBAND: Thank you.

JOHN DANKOSKY: Dr. Miriam Cooperband is a scientist with the United States Department of Agriculture Animal and Plant Health Inspection Service, Plant Protection and Quarantine Division. She’s based in Massachusetts.

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