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Meeting Their Match
INVASIVES WEEK: We’ll never be able to eradicate our most damaging invasive species. But by invading them right back, we might be able to fight them to a draw.

This story is a part of OnEarth's Invasive Species Week.

“We’re like the Sopranos,” Mark Mayer told me. “We kill things.”

Most government assassins wouldn’t put it so bluntly. Or maybe they would: I haven’t met too many government assassins. Maybe they like to amuse themselves, as Mayer does, by feeding the hallway crickets to the pet tarantulas they keep in their offices. Maybe they, too, work in facilities like Mayer’s: a gray box with a windowless brow, parked on the outskirts of Trenton, New Jersey, near the state police headquarters. Its warren of vault-like rooms offers morbidly minded visitors a panorama of grisly murder methods—mummification, fungal infection, ovophagy, parasitoid exploitation—suggesting that Quentin Tarantino may, in fact, be lacking in imagination.

All of which gave me hope. Because like most clients who walk through the front door of Mark Mayer’s office, I wanted someone dead. 


OnEarth goes in depth and up close on a growing global concern.

Invasive species are all around us. The definition includes any organism—plant or animal—that gets introduced into an ecosystem where it doesn’t belong (often by humans) and ends up wreaking havoc.

But that simple definition doesn’t convey the enormity and complexity of the environmental threat that invasives can pose. The introduction of a single nonnative species can set off a cascade of disruptions, devastating an entire habitat as it alters the landscape (or waterscape) and competes with native species for limited resources. Today, they’re affecting the United States from coast to coast: European green crabs are consuming our shellfish, gribble crustaceans are attacking Seattle’s waterfront seawall, wild boars are taking over our forests.

Invasive species are responsible for billions of dollars in economic losses annually; internationally, the yearly price tag is estimated to hover around $1.4 trillion. And that’s not even including those costs that can’t be accurately tallied until much later, such as the staggering loss of global biodiversity that can be laid at the feet—or the roots—of these unwelcome organisms.

The Nature Conservancy has estimated that 42 percent of current “threatened” or “endangered” species owe their troubled status to invasives. And because these species are often spread by global trade, which lies at the heart of our modern economy, the problem is only getting worse. But there’s hope! Scientists (and even some very clever restaurateurs) are working to minimize their impacts—and to avoid the next invasion.

It all started, as revenge sagas often do, in an empty field. At the edge of my property in New York’s Catskill Mountains one day, I stumbled upon a killing in (very slow) progress: tiny, wispy white balls nestled in the needles of a baby hemlock tree. I recognized them—the egg sacs of the hemlock woolly adelgid. Adelgids, broadly defined, are aphid-like insects that suck the life juices from conifers; the particular type of adelgid that was germinating in those white fuzzballs, Adelges tsugae, was a specialist. I had been expecting it. People had been telling me for some time that this cold-blooded killer was coming for the Catskill hemlocks. And now here it was, about to murder my trees.

I called a local arborist, a man of such formidable facial hair that our household knows him as “Whiskers.” Whiskers is a crack branch-trimmer, stump-grinder, and tree-feller—but the adelgids had him running scared. The horticultural oils I had read about online were not, he said, up to the job. There were pesticides, but they were so hardcore, he wasn’t certified to apply them. No, by his own admission, Whiskers couldn’t “take care of things” for me. Instead, he suggested I get some advice from the local county co-op extension.

And so—at the suggestion of an axe-toting man named Whiskers—I began a search that took me from my home in upstate New York up and down the Atlantic seaboard, all in search of a killer for hire: someone, or something, that could put an end to my adelgid problem once and for all. I wasn’t in any position to demand a no-questions-asked kind of arrangement. I had plenty of questions of my own.

* * *

Hemlock forests are common in the eastern United States from northern Georgia to Maine. Known to reach 160 feet in height, the trees can easily live for 600 years, producing cones for 450 of those years. They’re prime examples of what ecologists call a “keystone species”—one that essentially sets the terms of a given ecosystem. In the Catskills, their dense shade produces the distinctive mix of hardwoods and evergreens. Their thick growth along riverbanks shades streams, creating the cold temperatures necessary to sustain the region’s famous trout fishery.

Much of our eastern forest, though, has already been transformed by hemlock die-off. The fact that hemlocks don’t have the same timber value of other species—think ash or maple—can make it harder for scientists to get funding for research. The sad fact of the matter is that our nation may well lose an entire ecosystem if the hemlocks disappear. But it won’t lose billions of dollars, so action has been slow in coming.

And so, with little to go on but Whiskers’ tip and my own desperation, I started my journey by paying a visit to the Ulster County, New York, branch of the Cornell University Cooperative Extension—sort of like the FBI, if the FBI had satellite offices in drab strip-mall storefronts lodged between a Radio Shack and a martial-arts studio. Still, this is where you go when you’re in a situation like mine: They’re the ones with the right blend of data, manpower, and know-how to go after the bad guys. Their online rap sheet fingers many of the Catskills region’s most notorious invasives: Japanese knotweed, Oriental bittersweet, emerald ash borer, Asian shore crabs, mute swans, zebra mussels, quagga mussels, plum pox virus, Asian clams, killer shrimp, and giant hogweed (a kind of Queen-Anne’s-lace-on-steroids that makes your exposed skin bust out in blisters after ten minutes in the sunlight).

But while the helpful folks at the extension office had plenty of brochures on how to hack down knotweed, they went mum when I asked them about bumping off adelgids. That sounds like a job for Albany, they said. Call the New York State Department of Environmental Conservation. Ask for a guy named Denham.

“We used to get a major new tree pest once every 30 years or so,” Denham (first name: Jason) told me when we finally connected. “Chestnut blight, gypsy moths, and Dutch Elm disease back in the ’60s and ’70s. Now the volume of global trade is such that we seem to have a new forest pest introduced every few years.” In other words, it’s all about the ports. Trees, he said, are soft targets for invasives, since so much international trade involves the use of wooden shipping containers and pallets: Forest products, unsurprisingly, are great at transporting stowaway pests. Which helped explain why so many of these killers seemed to come from Asia. As Denham said, “We import a lot of goods from China.” And from Japan, too—the forensic foresters believe the hemlock woolly adelgid originally stowed away on a Japanese hemlock that was delivered to a nursery in Richmond, Virginia, sometime around 1950.

Denham and I talked some more. That’s when the context for my hemlock murder mystery began to widen, to extend far beyond my property in Ulster County. Invasives, you see, are in the midst of staging a national crime wave. At this very moment Seattle’s waterfront seawall is under attack by tiny crustaceans called gribbles. Asian carp are hoovering up everything in the Mississippi; now they, along with zebra mussels, are threatening to disrupt the entire Great Lakes ecosystem. Wild boars are ravaging our forests; nutria are destroying our coastal marshes; European starlings are edging out our native birds; European green crabs are snarfing down our shellfish; killer bees and red imported fire ants are stinging us to death.

Interdiction, practically speaking, is impossible. Ironically, the most promising solution, as Denham confirmed, is to bring in more invasives: to match each new invader with the natural predator that kept it in check back home. It’s called biocontrol, and it can be summed up in a single, hard-boiled equation: Got a problem with Invasive A? Bring in Hit Man B—he’s been naturally selected to know exactly what to do.

New York State has already been experimenting with adelgid control by releasing three insects widely known by scientists to go after them. Two of them, Sasajiscymnus tsugae and Laricobius osakensis, hail from Japan. But lately, Denham said, researchers have been having far better luck killing adelgids by matching them with a tiny beetle that’s actually native to the Pacific Northwest: Laricobius nigrinus. Western hemlocks, it turns out, have been afflicted by woolly adelgids, too—insects that are technically the same species as, but genetically distinct from, the Japanese invaders on the East Coast. Yet, curiously, the western hemlocks have somehow managed to survive. Many scientists suspect L. nigrinus is what’s helping keep the western woolly adelgids in check.

If it wasn’t a silver bullet, at least it was something to go on. But I’d have to follow through on my own. In keeping with the pattern, Denham passed me along to Cornell University’s Mark Whitmore, who has been staging biocontrol battles for nearly 20 years on a mini-plantation of four-foot-tall hemlocks that he has infested with woolly adelgids, as well as L. nigrinus beetles imported from the West Coast. Then Whitmore, for his part, followed suit, referring me to some of his colleagues at Virginia Tech University. There, I was told, I might get the fuller picture of how biocontrol works—as well as how it might or might not work, specifically, for the hemlocks in my Ulster County backyard.

* * *

Biocontrol isn’t a new idea. Just think about humanity’s long history of keeping cats to kill mice. But the strategy’s great leap forward, scientifically speaking, occurred in California during the late 1800s. The state’s hugely important citrus industry was under attack by an insect known as cottony cushion scale. Researchers traveled to Australia, where the scale had originated, and there they discovered a particular ladybeetle that clearly enjoyed eating it. These researchers brought some back to the United States. Within a year, the scale was beaten back, and the state’s orange crop was saved. Suddenly, biocontrol looked like a panacea.

What followed was a series of notable biocontrol successes—interspersed with some equally notable disasters. In Hawaii and Puerto Rico, for example, the Indian mongoose, released in sugarcane fields to eliminate rats and snakes, went on a rampage, killing native birds and annihilating 12 species of reptiles and amphibians. On the mainland, Asian carp that had been released in lakes to control the growth of invasive Eurasian watermilfoil, ate all the plant they could find—and then ate everything else they could find. (Today, the Army Corps of Engineers has had to resort to installing underwater barriers in the Chicago ship canal to try and keep Asian carp out of the Great Lakes.)

And then there’s the story of the cane toad. Biocontrol’s most high-profile failure, the cane toad was introduced in Australia to devour the crop-destroying cane beetle but later went on to kill any local fauna unlucky enough to ingest its highly potent venom. (It also menaced public morals, once people figured out that licking the toad’s neurotoxin-laced skin produced a cheap, if socially awkward, high.) As in many other instances of biocontrol-gone-awry, the Australians ultimately began investigating new biocontrols to help control their old biocontrols, resulting in a real-life iteration of the problem experienced by that old lady who swallowed a fly.

Today, in the United States, biocontrols are strictly regulated under the USDA’s Animal and Plant Health Inspection Service, which stipulates that no non-native biological agent can be released on these shores without undergoing years of evaluation—initially in the agent’s native country, and then here, under strict quarantine. Even beneficial insects that originate from within America must be evaluated and approved by those states where they will be released. The evaluation process is exacting. First, the insect must be proven to be “host-specific”—meaning it will only prey on its intended target. (To test for host specificity, scientists force-feed the “beneficial” insect a variety of non-target species; if it can survive on them, it’s rejected.) If the host-specificity hurdle is cleared, a technical advisory group is convened and a larger environmental assessment is completed. Then, once the insect’s release has been approved by the U.S. Fish and Wildlife Service, the USDA, and the EPA, individual states get to weigh in. This level of caution and intense regulatory scrutiny helps explain why the search for an effective woolly adelgid predator has taken 20 years to start making headway in the eastern United States.

The insectary at Virginia Tech University is a redbrick cube appended to a row of greenhouses. When I arrived, bearing Mark Whitmore’s recommendation, a woman named Carrie Jubb (official title: Insect Mass Rearing Supervisor) met me at the door. She was drinking coffee out of a mason jar. Behind her was a horror-movie-style poster depicting L. nigrinus squaring off with an adelgid. “Bugzilla vs. Woolly Adelgid!” it read. “These tiny beetles are our greatest hope!”

“We’re reconnecting the natural enemies with their hosts,” Jubb’s colleague, Scott Salom, a professor of forest entomology, later told me. “But ecologists have had serious issues with biocontrols”—and in many university ecology departments, he added, “they tend to teach that. So people who have taken ecology courses may come away thinking, ‘What are we doing to the environment? We’re playing God; we’re altering something that’s not meant to be.’ But the reality is, we’re trying to get it back to some simulation of its natural environment.”

That declaration may still not be very convincing to some ecologists. But Salom, while he believes we should all be working to preserve as much native habitat as possible, is no longer asking How can human beings stop altering the environment? Instead, he says, the question should now be, What kinds of environments should humans, through their alteration, seek to create? Or, to put it another way, don’t we have some kind of responsibility to correct the ecological imbalances we have already caused—even at the risk of blowback?

Salom thinks so. And that’s why, in the late 1990s, he and his colleagues at the Virginia Tech insectary began their pioneering research into the rearing and release of L. nigrinus to combat the woolly adelgid plague that was afflicting eastern hemlocks. The process itself is “very tedious,” Jubb admitted to me, as she showed me around a temperature-controlled room stacked with mason jars like the one I’d just seen her drinking from. Except these jars weren’t filled with coffee; they were filled with L. nigrinus beetles that had just emerged from their summer dormancy—and they were ready to eat. 

At the insectary, lab workers collect beetle larvae in the spring and put them on soil samples. The hatched beetles burrow down and pupate. In the fall they emerge— hungry. One lab worker’s job is to scour the countryside for infected branches: beetle food. Technicians with aspirators that look like turkey basters then go through the branches and collect the pinhead-sized predators, one at a time. Most get packed into FedEx boxes and shipped off to the various agencies, such as the U.S. Forest Service and the National Park Service, that oversee their release. A few beetles are left behind to help propagate the next generation.

There are definitely signs of progress in the war between L. nigrinis and woolly adelgids, but they don’t necessarily come quickly or easily. In this way, it’s a little like the drug war. To date, cooperating agencies have released thousands of beetles—but the adelgid numbers are, by comparison, enormous. As law-enforcement officials have learned, the world’s a big place when you’re trying to track down a kilo of cocaine. Turns out it’s an even bigger place when you’re trying to track down an insect the size of a comma.

“We need more predators out there if we’re going to have an impact in the short term,” Salom said. “With Laricobius nigrinus, the total number of beetles we’ve put out into the environment is a little more than 200,000. The problem with this insect is that it’s hard to rear in tremendous numbers. Now, if you were talking about Trichogramma”—a parasitoid wasp often used to combat cotton bollworms, apple moths, and corn borers—“you can buy them commercially. You can get 12,000 for, like, $20, and release the parasitized eggs in your cornfield. They’ll hatch and do their thing.”

But not so with L. nigrinus? Was that the implication? I told him this was exactly what I was hoping to do: purchase a bunch of beetles, then release them all at once onto my hemlocks.

By way of indirect reply, Salom said, “Nobody’s figured out how to make money on this yet. The government will help develop the technology, and they’d be happy for a private company to take this on. But the market has to be there for them to be self-sustaining.” In other words, economies of scale weren’t working to my advantage. Perhaps I could get my hands on some beetles and put them on my hemlocks. But when those beetles ate the last of the adelgids, more adelgids would simply arrive. Eventually my small, private army would be defeated.

Once again, I felt as if my hemlocks were being punished for their relatively low market value as a source of timber. A landscape-scale threat, like a forest pest, requires a landscape-scale solution. And in our world, at least, those solutions are far more likely to emerge when there’s a cash crop at stake.

Given the economic realities of the situation, I asked Salom if he didn’t sometimes worry that his and his colleagues’ efforts would largely end up being in vain. If the money and momentum always end up going toward cash crops at the expense of ecosystems, didn’t the current war to save the hemlocks qualify as a losing battle?

“That’s no reason to let it happen now,” he insisted. “You fight it now because you can—because you can show some success and prevent things from getting out of control. These pests come in; they’re catastrophic. If they’re catastrophic, why allow more catastrophe?”

* * *

Back in Trenton, Mark Mayer was more upbeat. “The hemlocks aren’t all going to die like everyone, 20 years ago, thought they were going to die,” he told me. “On marginal sites”—meaning sites where it’s extraordinarily dry, for example—“they may have a harder time. But we’re not going to lose all our hemlocks.”

Mayer was showing me around his lab, the Phillip Alampi Beneficial Insect Laboratory, which is run by New Jersey’s Department of Agriculture. New Jersey happens to have a very strong biocontrol program—in part because it happens to have a very bad mosquito problem, and the lab is experimenting with biocontrol as a mosquito-management technique. Phillip Alampi is a state-of-the-art facility where scientists are rearing a variety of insects to control a wide range of invasive threats to agriculture and native plants.

Don’t we have some kind of responsibility to correct the ecological imbalances we have already caused—even at the risk of blowback?

In his office, Mayer showed me photographs of one of his favorite bugs, a weevil that feeds on a highly invasive weed that goes by the name of mile-a-minute. “They’re really cute,” he said. “They’re really tiny, and they waddle, then they’ll do these little somersaults. It’s my co-favorite with Laracobius.” (Later, he rather touchingly felt the need to clarify: “I don’t really like one more than the other. It’s like picking between your children.”)

Mayer also had good news about the pretty but highly invasive plant known as purple loosestrife, which came over from Eurasia in the early 1800s and has been wreaking havoc on our wetlands ever since. “We don’t have to hate loosestrife anymore,” he said. “It’s an excellent nectar source for bees. And it’s not going to take over our wetlands anymore.” That’s in large part thanks to a tag team of beetles that his lab is rearing to keep loosestrife in check.

The goal, Mayer emphasized, isn’t eradication: it’s balance. Keep pests like mile-a-minute or purple loosestrife—or woolly adelgids, for that matter—down to a manageable level. Keep the devil down in the hole.

At one point, Mayer led me into a host-rearing room where tarnished plant bugs—a family of insectoid pests that preys on small fruits and vegetables—were being introduced to a parasitoid wasp. (“Have you ever seen the movie Alien?” he asked with undisguised relish. “You know how the monster works? That’s how this parasite works! But the bug dies first; the wasp doesn’t come out while the bug’s still alive. They did that for dramatic effect.”) In the next room, a pile of butternut squashes afflicted with San Jose scale were providing dinner for a flock of beetles. In the room after that, a parasitoid wasp had injected its eggs into Mexican bean-beetle larvae. A technician was collecting the dead larvae, the accepted scientific term for which is actually “mummies.” Wasp larvae were living inside them. “They’re pretty impressive,” Mayer said. “Since 1987, no soybean farmer has had to spray his crop for Mexican bean beetles.”

Towards the end of our conversation, I asked Mayer if he ever felt funny about being a government hit man—even if his hits were only plants and bugs. “All living things live at the expense of other living things,” he said. “There’s no exception. In order for us to live, something else has to die.”

The L. nigrinus in Mayer’s lab were already spoken for: They were headed for New Jersey and Pennsylvania. But true to his nature, he was optimistic that when the beetles ran out of adelgids to eat there, they’d find their way to other adelgid-infested hemlock stands—including the one in my little corner of the Catksills. “The Laricobius are probably going to get to your place in ten years,” he told me confidently.

Perhaps, I thought, his insect assassins would get to my trees in time. Perhaps catastrophe would be averted, or at the very least, forestalled. But when I asked him if I could take some beetles home in a jar, he just smiled.

“They’ll get there,” he said.

Something about his tone of voice made me think that asking twice wouldn’t have been a good idea.

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image of Ginger Strand
Ginger Strand is the author of a novel, Flight, and two books of nonfiction: Inventing Niagara: Beauty, Power, and Lies and Killer on the Road: Violence and the American Interstate. She writes for a variety of magazines, including Harper’s, Wired, and Orion, where she is a contributing editor. MORE STORIES ➔