Back in the late 1880s, California citrus farmers found themselves dealing with a crisis caused by a fat bug covered in a shieldlike, granular white wax. Known as the cottony cushion scale, this insect, which had hitchhiked aboard ships from Australia, usually spends its entire life with its mouth affixed to a single plant, greedily sucking out nutrients. Now the bugs were making meals of the state’s citrus trees.
Some farmers resorted to erecting large canvas tents around their trees and fumigating the inside with hydrogen cyanide in attempts to murder the insect, which proved ineffective. That’s when Charles Valentine Riley, who pioneered the field of entomology in the United States, was called in.
In his role as chief entomologist of the U.S. Department of Agriculture, Mr. Riley sent an assistant to the land down under in 1888 to hunt for the bugs’ natural predator. Within three months, a shipment of small branches arrived in California. The branches carried not only cottony cushion scale, but also another bug: the Vedalia beetle, a species of ladybug and a natural predator of the scale. As more shipments arrived, entomologists in California bred the beetles and eventually released them, marveling as the ladybugs dined ravenously. By the end of 1889, the fat cottony cushion scale was no longer a grave threat to citrus growers.
“It’s hard to imagine what California’s economy would have been like if citrus had collapsed and never taken off,” said Mark S. Hoddle, an entomologist at the University of California, Riverside.
The sharp reduction of cottony cushion scale was one of the United States’ first large-scale programs in biological control, the broad term for using one organism — an animal, a fish, an insect or even a bacterium — to suppress another organism. These efforts won’t fully eliminate a targeted pest. But if done right, they can drive down a pest population to levels where future damage is minimal.
Debates over biological control are resurfacing as U.S. entomologists seek to do something about another pest in their cross hairs: the spotted lanternfly, a winged insect that feasts on vineyard vines, fruit and forest trees. Baby lanternflies start to hatch in May and begin to grow into adults over the summer. Come July, millions of people on the East Coast, from New York to Virginia, will start to see lanternflies overhead and on the ground. Some models predict the bugs could be in California in less than 10 years, ready to pounce on the vines vital to the state’s $88 billion wine industry.
American scientists, Dr. Hoddle included, are actively studying a nonnative biocontrol agent right out of a bug’s worst nightmare: parasitic wasps. Praise God they’re not harmful to people or pets, because these wasps reproduce by laying eggs in or on the bodies of other host species. Researchers are investigating their potential to curb the lanternfly population, which has reached frightening proportions since the bug made its way into the United States from China, its native land, to Pennsylvania in 2014. Many believe it arrived via a shipment of landscaping stone. Therein lies the rub. The increasing scale of trade and globalization makes biocontrol a rather anthropocentric exercise. The species humans deem as pests, be they bugs or vegetation, often make their way into unwanted geographies on the backs of human activity. We play a central part in upending ecosystems — and then we come along again to forcibly restore balance.
Over the past 150 years, more than 2,000 species have been released worldwide to subdue invasive populations. But willingly altering a native ecosystem can be fraught with risk and uncertainty. A Hawaiian entomologist, Francis Howarth, outlined his concerns over biological control in a 1983 paper, noting that many animals “broaden their diets” when introduced into new geographies and sometimes become “detrimental instead of helpful.” That contributes to biological pollution, which he defined as “the establishment in the wild” of any nonnative organism.
I was initially skeptical of biocontrol. I nervously wondered to what extent humans can responsibly harness natural ecological relationships to fix the very problems that globalization and human activity have caused. At what point does intervention cross into interference?
Yet my position has shifted. I’ve come to see biocontrol as neither panacea nor Pandora’s box, to use Howarth’s description. Rather, it’s more nuanced, and even more effective, than I thought, and society’s view of how to combat invasive species ought to be more generous to solutions that, at least on the surface, seem radical.
This isn’t to excuse biocontrol efforts that are executed clumsily or incompetently. History is full of bungled attempts. Two decades before the ladybugs’ success in California, another tree-killing outbreak occurred on the opposite side of the country. In the 1860s, a man in Medford, Mass., keen on finding a moth more favorable for silk production, imported a colony of European gypsy moths, which promptly escaped from his home and established themselves in neighborhood trees. Over the next decades, they dispersed all over the Northeast, defoliating acres of forest along the way. Once again the U.S.D.A. got involved (although not under the seasoned hand of Mr. Riley, who died in 1895). Officials turned to Europe, where they found a parasitic fly that injects larvae into gypsy moth caterpillars’ bodies. The larvae eat the caterpillars from the inside, killing them.
The parasitic fly was released into the United States, where it killed gypsy moths. But it also attacked more than 180 other species of native insects, including cecropia moths, the largest moths in North America. To this day, populations of cecropia moths have plummeted wherever great numbers of this European parasitic fly thrived. Such is the nature of biocontrol: When it fails, it fails big.
In 1930s Australia, gray beetles were running wild over the continent’s sugar cane fields. Cane toads were imported to solve the problem and now overwhelm neighborhoods, nearly 100 years later. More than just a nuisance, when the toads are stressed, they release a toxin powerful enough to kill cats, dogs and other animals, including crocodiles, that cross paths with them.
Like so many things in science, judging a practice solely on its worst outcomes can make for shortsighted decision-making. It risks closing us off from opportunities at improving an approach that’s also shown the potential for great reward.
“When we succeed, an invasive organism doesn’t become a huge problem and nobody hears of it,” said Juli Gould, a former researcher with the U.S.D.A. Animal and Plant Health Inspection Service who has more than 40 years of experience in biological control. (Before she retired last year, she was searching for a parasitic wasp that might combat the spotted lanternflies.)
No one, Dr. Gould contends, has heard of the ash white fly, a scourge in Southern California in the early 1990s. The fly fed on ash trees, as well as citrus and fruit trees. It also, like the spotted lanternfly, secretes a sweet substance called honeydew, which drips onto leaves, eventually producing a black, sooty mold that impedes photosynthesis. Researchers found a parasitic wasp native to the Mediterranean that attacked ash white flies and released the wasps in California, and soon the ash-tree eaters ceased to be a plague.
What made this wasp so good at homing in on ash white flies was an element that remains central to biocontrol regulation today: host range, the number of species an antagonist organism is able to attack. The parasitic wasps that went after ash flies had a narrow range, only targeting a few species. Now compare that wasp to a cane toad, which will pretty much eat anything it can fit into its mouth.
Biocontrol’s proponents argue that grading its value based on events from the past is a false equivalence. That strikes me as true. We might hear about the biocontrol attempts that don’t work and then project those failures onto any future endeavor at curbing an invasive organism.
“Projects fail for various reasons, the big one being not enough resources were devoted to making them successful,” Dr. Gould said. “But economic analyses have shown that although all projects do not succeed, biocontrol has such a positive benefit-to-cost ratio that it is still worth pursuing.”
And that’s to say nothing of how biocontrol has continued to reform. The current system in place in the United States to combat, say, a nonnative weed with a biocontrol agent requires scientists to extensively study whether the proposed agent can effectively stop the proliferation of the target species and avoid affecting desirable plants, like farmers’ crops. Introducing it to the wild then requires a review by several agencies and entities, including the U.S. Fish and Wildlife Service, a consultation with tribal nations that might be affected, comments from the general public and input from representatives from Canada and Mexico. (A very similar process is required to introduce any nonnative organism intended to target an invasive insect.)
According to Jennifer Andreas, a professor at Washington State University and the weed biocontrol specialist for the state of Washington, this regulatory process can be completed in two years, though that rarely happens. It more often takes at least three years, and sometimes as many as 15, to ensure biocontrol agents are safe to release. Of more than 500 biocontrol agents released worldwide to combat invasive weeds, only three of them, according to the available data, have a negative impact on native plant populations, Ms. Andreas said.
According to a review done in 2020, every dollar spent on weed biocontrol leads to at least an $8 dollar return on investment, thanks to reduced weed impacts.
The real problem, quite simply, is human nature. “People go on vacation, they see a pretty plant, they’re like, ‘I’ll take these seeds, grow them in my garden,’” Ms. Andreas said. “Sometimes we don’t know things would be a problem until it’s too late.”
So where does that leave us with a pest like the invasive spotted lanternfly? I’d say stomp the suckers whenever you see them this summer and bring on the wasps. Saving the country’s vineyards and forests is paramount, but we’d do well to consider the larger stakes of allowing these insects to spread more aggressively across America. We should try to find a means of biological control for lanternflies and be careful as we do it — positions that aren’t mutually exclusive.
It’s a tricky calculus. One parasitic wasp sourced from lanternflies in China has already been excluded from further research. It attacked the eggs of the spotted lanternfly, but it also parasitized the eggs of native American stink bugs and moths.
“It’s not like we go to China and get some parasites, bring them back to California, and just start throwing them out of the window of the car as we drive up and down grape fields,” Dr. Hoddle said. “I don’t want to be responsible for releasing something and they call it the ‘Hoddle Plague’ that destroyed California.”
Who would? There are rights and wrongs to human interference, no doubt. In this janitorial role that biocontrol often inhabits, we’re often cleaning up messes of our own making. And while there’s no turning back the clock on globalization, it has also made it possible to address some of these problems.
Dr. Hoddle knows this all too well. More than 100 years after cottony cushion scale was inadvertently transported to California, the bug arrived on the Galápagos Islands, in the 1980s. The scale threatened endemic island plant species. The challenge of the outbreak of cottony cushion scale was one that researchers had met. Ladybugs were released on the Galápagos — a project Dr. Hoddle participated in — and again waged war. That biocontrol program continues to be a success. It’s also a reminder that doing nothing is rarely neutral.
Source images by Eric Dale Creative, Danut Vieru, Alekss via Adobe Stock; Bill Boch, Moppet via Getty Images; and Donald Hobern.
Andrew Zaleski is a freelance journalist and a contributing writer for Washingtonian magazine.
The Times is committed to publishing a diversity of letters to the editor. We’d like to hear what you think about this or any of our articles. Here are some tips. And here’s our email: [email protected].
Follow the New York Times Opinion section on Facebook, Instagram, TikTok, Bluesky, WhatsApp and Threads.
The post Squashing Spotted Lanternflies Will Get Us Only So Far. We Need Wasps. appeared first on New York Times.
