Short Wave - A Pesky Rumble: Pink Bollworms Vs. Cotton Farmers

Episode Date: January 25, 2021

The pink bollworm — an invasive species that plagues cotton farmers around the world — has been successfully eradicated from much of the U.S. and Mexico. Eradication campaigns rarely work, but this one did. NPR food and farming reporter Dan Charles gives us the play-by-play to how it took two concurrent approaches to eradicate this devastating pest. Email the show at [e-mail] pcm.adswizz.com for information about our collection and use of personal data for sponsorship and to manage your podcast sponsorship preferences.NPR Privacy Policy

You're listening to Shortwave from NPR. Hi, everybody. Maddie Safaya here with NPR Food and farming reporter Dan Charles. Hi, I'm Mattie. Dan, I'm hoping you are here with more bug-related reporting. It has been a while since we've tackled the invasive species beat together. You've told us all about invasive lanternflies, other insect pests that eat farmers' crops. You've answered our listeners' questions about invasive species. Yes, Maddie.

And I am here with another bug story, but this one is totally different. Oh, my God. I'm so ready, Dan. Let's go. It's an incredible battle. In this corner, we've got billions of little pink caterpillars, tiny things from across the Pacific. Love to chow down on seeds inside bowls of cotton, incredibly destructive. And on the other side, in the other corner, we've got cotton farmers in the southwestern U.S.

They've cooked up a wild scheme to wipe out the bug. eradicate it from Arizona, Texas, New Mexico and Mexico. Dan, are you sure you're not a wrestling announcer? Oh, yeah. Okay. Okay. All right. That does sound like a wild battle, Dan, and also like kind of impossible

to eradicate it? Yeah. Like, who actually completely gets rid of an invasive species? Right. So that is what Bruce Tabashnik thought. He's an entomologist and he studies exactly this sort of thing at the University of Arizona. I guess as a biologist, as an evolution,

evolutionary biologists as someone who studies evolution of resistance and insects. The first thought is always that the insect will adapt. There's something missing in your process if you think you're going to overcome the insect. I say that every day when I wake up, Dan, you know? Okay. Okay. So who won this battle, the farmers or the bugs? Patience, Maddie, will get there.

But I'm going to tell you the whole story from the beginning. And it involves genetically engineered crops. It involves scientists dumping billions of sterile bugs out of airplanes, sex pheromones. And Bruce Tabashnik is still kind of amazed at how it turned out. I think it's stunning. And that's one of the reasons I want people to know this story. Right now, very few people know about it. So today on the show, the fight to eradicate a tiny pink caterpillar decimating cotton crops in the southwestern United States.

You're listening to Shortwave from NPR. All right, Dan, what is this little pink bug? What's it about? Okay. It's called the pink bowlworm. And I found a guy who has seen more of these little creatures than he ever wanted to. My name is Carl Button. Carl is a cotton farmer in Arizona.

He rents land from people in the Gila River Indian community. Now, 30 years ago, he would go out to his fields. He would pick out some cotton bowls, which are the little pods where the cotton fiber. grows. He would cut them open looking for these tiny little red worms. And you could find three or four worms in the same bowl, and they were all different ages, different generations. And that was a really, really serious problem. Dan, why is that such a problem just because they're going to do so much damage to his crops? Right. There's so many of them. But also because these different generations, he knows that in order to kill them, he was going to have to keep spraying this

field with some pretty nasty chemicals for weeks into the future. See, those pesky little insects, they spend the first part of their lives tucked away inside these cotton bowls and then right after that in cocoons in the soil. And that whole time, Carl could not get at them. You know, they were protected. His only chance to kill these pests was later when they emerge as moths, flying around looking for mates. This one here will be out in a week.

This one here will be out in 14 days. This one here will be out in 21. this one here, and take until 28. I've got to have this field painted, you know, for 28 days with enough to kill a frigging dinosaur. Wow. Okay. So at this point, his choice, Dan, is either spray like crazy or flat out lose his crops? Yeah, pretty much.

I called his pest control advisor, a guy named Tom Montoya. He is the person who works with a lot of different farmers like Carl Button and tells them what they have to do. to control their insects. And he was saying the pink bullworm was a terrible problem all across this region for cotton farmers, especially in the 1980s and the 1990s. It was ugly. Basically, it was people were spraying 12, 13, 14 times. Some guys were spraying more than that.

Some guys were less. That's 12 or 13 times in one growing season. And, you know, fun fact, Maddie, a lot of them were doing this with airplanes, flying in the middle of the night because that's when the moths come out. So on top of needing chemicals for just this one pest, they're flying at night, which seems, you know, maybe kind of dangerous to me, not to mention pretty expensive. Right. And the thing is, it didn't even work very well. People went to debt, lost farms, took a lot of financial damage, and there wasn't an end in sight.

No end in sight until about 25 years ago the tide starts to turn because cotton growers got a new weapon against the pink bullworm. And the weapon is called BT Cotton. Oh, yeah, Dan, we talked about this the last time you were on the show, this cotton that's been genetically modified. It has a gene that's been taken from a kind of bacteria, bacillus thurian gensis, and it makes the cotton plants poisonous to certain insects, right? Yeah, exactly. the original GMO, right? And for the cotton farmers, it worked so well. It was a salvation.

But Dan, last time you were telling us that BT crops aren't working so well anymore, that the insects are becoming resistant to BT because farmers have been overusing it in a lot of places. Right. And that is still true. And it was a risk for the pink bullworm. In fact, in India, a new strain of the pink bullworm, that is immune to BT. But this story I'm telling you today is a kind of counter example. Because in the Southwest, cotton growers really did the right thing.

Along with the BT cotton, they planted these so-called refuges of non-BT cotton, just so they wouldn't have a situation where the BT was everywhere. And then the only bullworms that survived were those few rare ones that were immune to it. Right, because if there's still plenty of non-BT cotton, lots of regular pink bull worms are surviving, and that resistance strain won't have the opportunity to become, you know, the only bug in town. That's right. That's right.

Now, the thing is, even though farmers were planting those refuges and there was no resistant pink bullworm emerging, Carl Button says some of these farmers were not happy about it because, you know, first of all, they're paying for the BT cotton, which costs them a lot of money. And then they still had to plant these refuges, which were basically pink bullworm nurseries, you know, keeping some of the enemy alive so they didn't all become resistant. So there was a push on to find a way to just eradicate the pest. They said we think we can wipe it out entirely. And part of their plan for doing this was planting completely BT cotton.

I mean, Dan, that sounds like a recipe for creating a strain of insects that's resistant to BT. Yeah, exactly. the thing that the refuges were supposed to avoid. So this is what Bruce Tabashnik is thinking, you know, that entomologist at the University of Arizona. My stomach was churning and I was trying to figure out how I was going to tell these guys, no, no, don't do this. But here we get to a twist in the story because the cotton growers had another weapon in their arsenal. Sterile pink bullworm moths. Oh, yeah.

I know a little bit about this because we did an episode about it. It's an insect control technique that a couple of scientists from the USDA pioneered decades ago to control another tricky insect, screwworms. That's right, Maddie. And the thing is, they already had some practice doing this with pink bullworms, too, to keep the pest from spreading to other parts of the country. So the farmers in Arizona were saying, look, BT has reduced our pink bullworm population so much. Now we can just overwhelm them with these sterile insects and wipe them out. So they came to Bruce Bashnik, our skeptical scientist, and they asked him to do some computer simulations of this, calculate how likely it would be to succeed. We ran the simulations, and pretty much no matter how we tweaked it, it always worked.

So these computer models showed that they could completely eradicate the pink bullworm if they planted all BT cotton and also released these sterile moths. Right. Yeah. Basically in his simulations, No resistant strain of pink bullworms emerged because the sterile moths basically had replaced the refuges. Any of those rare resistant moths, you know, that emerged, able to survive the B.T. Cotton. Instead of mating with other survivors and producing resistant offspring, they made it with these sterile moths instead and produced no offspring. So eventually, you know, Bruce said, okay, I guess it'll work. and he went along with the farmer's eradication plan. And it got launched in 2006.

So as this gets underway, what are you thinking? Honestly, even though, I should tell you, even though the simulation said it would work, I guess in my heart of hearts, I still didn't think it would work. I get that, Dan. I mean, I've had these days thinking, all right, this is what my calculations say will happen,

but I must have screwed this up somehow. I must be missing something. It's like a classic scientist mentality. Right. So, you know, with doubt in his heart, they went ahead of this. The cotton farmers planted all BT cotton. The USDA's insect factory rolled out as many sterile moths as it possibly could. Over the course of the eradication program, more than 11 billion sterile pink boer worm moss were released by airplanes over every cotton field in the state of Arizona. Wow. Yeah. And to see whether. it was working, they set up a network of pheromone traps. You know, these are traps with a scent

that female pink bullworms released to attract males. You know, so basically, you know, the pink bullworms flock to these traps if they're there. And if you were making a graph to show the number of insects caught in these traps over the years, the line dropped like it was falling off a cliff. So it went from over 600,000 to one from 2006 to 2012, and then 2013, 14, 15, 16, 17, and 18, I can say 19 and 20 now, all zero. Zip, Zolt, nada, Bubkus. The scientific terms, Dan, the scientific terms. Okay.

So his computer simulations were right, but, I mean, Dan, come on, is it really gone, gone? It seems like it. In 2018, the USDA declared the pink bullworm eradicated in the southwest. Cotton growers basically don't have to worry about it anymore. The campaign wound down. They're not dropping sterile moths anymore. But the traps are still out there to detect any of the insects that might have survived or somehow, you know, caught a ride in from somewhere else.

Because, you know, that pest control advisor we heard from Tom Montoya, he is still on guard. There's got to be one out there. I mean, you just can't forget about it. I mean, it's a horrible pest. I'll tell you what, Dan. I identify with Tom's anxiety. For sure, for sure. So is there a lesson in this apart from, you know, don't trust your heart, trust the computer?

Well, Bruce thinks there is. He and some colleagues just published a paper about it in the journal PNAS. And he says this really only happened because they were able to combine these two different powerful tools. the BT Cotton and the sterile mods. Because neither one of them by itself would have worked. Scientific collaboration, Dan. It's what it's all about, you know? Absolutely, Maddie.

And in journalism, too. That's right. That's right. All right, Dan. Thank you so much for coming on the show to give us some good news today. We appreciate you, as always. Thank you, Maddie. It's always fun to be here.

This episode was produced by Thomas Liu, edited by Giselle Grayson, and fact-checked by Ariel Zabidi and our new intern, Rasha Aidi. Welcome, Rasha. The audio engineer for this episode was Patrick Murray. I'm Maddie Safaya, and you're listening to Shortwave from NPR.