Native predators and pathogens can provide effective, cost-free biological control of invasive species, as demonstrated by the American robin, European starling, and native microsporidian pathogen (Ovavesicula popilliae) that have been suppressing Japanese beetle populations across the United States for over a century without human intervention.
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America Spent $2.5 Billion Fighting Japanese Beetles. The American Robin Did It For Free追加:
The pesticide industry sells over $2 billion worth of insecticide every year in the United States to control a single beetle.
The federal government has been funding Japanese beetle research, eradication zones, and quarantines for more than 100 years.
The state of California has banned the import of out-of-state nursery stock for decades to try to keep them out. Most of it has not worked.
Japanese beetles are now established in over 30 US states.
They feed on more than 300 species of American plants, roses, grapes, raspberries, sweet corn, soybeans, and the roots of the lawn outside your window.
They were first found at a single New Jersey nursery in 1916.
They have been winning the war for more than a century.
But there is a part of this story almost nobody has heard.
In 1988, in a single field in Connecticut, an entomologist examining sick Japanese beetle grubs under a microscope found something nobody had been looking for.
A native microscopic pathogen already in the soil, already infecting the beetles, already cutting their reproduction in half, that the entire pesticide industry had been ignoring for 72 years.
It is not the only thing in your backyard that has been working on this problem without our help.
The robins on your front lawn, the starlings in your fruit trees, the hen scratching the corner of your garden, a small fly that lays its eggs on the back of every beetle that flies past [music] your roses.
The native predators have been here the whole time.
We just kept looking past them.
The Japanese beetle did not sneak into the United States [music] the way most invasive insects do.
It arrived in a parcel of iris bulbs.
Sometime before 1916, a shipment of ornamental iris from Japan was unloaded at a nursery in Riverton, New Jersey.
The Federal Horticultural Board had only begun inspecting plant imports in 1912, and the beetles riding inside the bulbs slipped past.
By the summer of 1916, a single nursery worker noticed metallic green beetles he had never seen before eating his rose bushes.
He took one to the New Jersey Department of Agriculture.
It was identified as Popillia japonica, the Japanese beetle.
Native to the home islands of Japan, where it lived under regulation by a community of specialized predators and pathogens that did not exist anywhere in North America.
By 1920, the beetles were established across four counties of New Jersey.
By 1930, they were in Pennsylvania, Delaware, Maryland, and New York.
By 1937, the first specimens turned up in Kentucky on the outskirts of Louisville.
By 1980, the beetle was in nearly every state east of the Mississippi.
The damage was not abstract.
The Japanese beetle does its work in two phases.
The adult beetles, in midsummer, congregate in feeding groups of dozens or hundreds, skeletonizing the leaves of more than 300 host plants.
They strip rose bushes overnight.
They leave grape leaves looking like brown lace.
They cluster on Linden, on Norway maple, on raspberry canes, on the tops of soybean rows.
Then, the females drop into lawn turf and lay their eggs.
The larval phase is what destroys the lawn.
White, C-shaped grubs, about an inch long, feeding on grass roots from August through November and again in spring, severing the turf from the soil so completely that an infested lawn can be rolled up like loose carpet.
The US Department of Agriculture has, by some estimates, spent over $460 million in cumulative federal funding on Japanese beetle eradication, monitoring, and research since 1916.
The American consumer pesticide industry has built an entire product category around lawn grub control.
The store shelves of every Lowe's, every Home Depot, every hardware store in the eastern United States carry between 15 and 40 separate products marketed against this single insect. Most of it works for about 10 days.
And while we were spending those decades chasing chemical solutions, a slow, unglamorous, mostly uncounted natural response was already underway.
Through the 1970s, 1980s, and 1990s, entomologists at universities across the infested range, Daniel Potter at the University of Kentucky chief among them, began publishing studies that did not fit the dominant narrative.
The dominant narrative was that Japanese beetles had no effective natural enemies in North America.
That the absence of co-evolved specialists from Japan meant the beetle would expand unchecked until pesticides or imported biocontrols caught up.
The study showed something more complicated. North American generalist predators, ground-dwelling beetles, ants, soil-burrowing wasps, foraging birds, and native pathogens were attacking the Japanese beetle at every life stage. None of them were specialists. None of them had evolved alongside the beetle.
But together, in a forest or a suburban lawn left alone, they were doing measurable work.
In a single Iowa study, native generalist predators were estimated to be killing the majority of Japanese beetle eggs in untreated turf plots before the grubs ever hatched.
In a single Connecticut field in 1988, a researcher found something that nobody had named yet.
Three layers of native defense.
All of them already in place.
All of them, in some cases, doing more than the lawn care industry's products.
The first layer is the one most people see.
European starlings, themselves an invasive species brought to North America in the 1890s, descend on Japanese beetle infestations in flocks.
>> They feed in groups of 20, 50, sometimes over a hundred birds, picking adult beetles off the foliage of orchard trees and roses, and probing lawn turf for grubs with a foraging technique called open-bill probing. Driving the closed beak into soil and prying it open to expose what is hidden underneath.
Behind them come the native birds, the American robin, the common grackle, the blue jay, the northern cardinal, the eastern bluebird, the catbird.
The European starling is the most efficient adult beetle hunter on the lawn. But it is one of dozens of bird species documented feeding on Japanese beetles in North American studies.
Researchers at the University of Kentucky have noted for over four decades that lawns with heavy Japanese beetle grub populations are visibly disturbed by bird foraging.
Robins, starlings, and crows leaving small pockmarks across the turf as they extract grubs by the dozen.
>> [screaming] >> The grubs do not get away.
A Japanese beetle grub the size of a man's thumbnail is, for an American robin, one of the most calorie-dense items it can find in a suburban yard.
A single feeding bird working a heavily infested lawn for an hour will eat 15 or 20 grubs.
Multiply that across a yard, a neighborhood, a county.
The number of Japanese beetle grubs removed every spring and fall from the lawns of the Eastern United States by birds that nobody is paying anything to is somewhere in the tens of billions.
It is one of the largest unpaid pest control operations in North America.
And it has been running in plain sight since the 1920s.
And underneath it is something nobody is paid to see.
There is a question worth asking before we go further.
If native birds have been eating Japanese beetles for a hundred years, why has the population not crashed?
The answer is the math of a generalist predator versus a fully established invasive population.
A robin will eat as many beetle grubs as it can find, but it will also eat earthworms, native insect larva, fruits, and seeds.
Its population does not increase proportionally to the beetle population the way a co-evolved specialist would.
A specialist predator from Japan, a parasitic wasp or fly that has evolved to target only the Japanese beetle, would have its life cycle locked to the beetle's life cycle.
As the beetle population rose, so would the specialists until the two reached equilibrium at low density.
That specialist did not arrive with the beetle.
It is still not here in any reliable form.
What we have instead is what ecologists call a generalist response.
A loose coalition of birds, soil-dwelling predatory arthropods, and native pathogens, all of which take some Japanese beetles when they happen to be available.
The population is not crashed, it is suppressed.
The suppression is real.
The studies show it.
The lawns of the Eastern United States hold fewer grubs than they would without bird predation by a margin that researchers have measured in the tens of percent.
And in the layer below the lawn, the third [music] native predator, discovered late, ignored longer, and still not in the public conversation, has been doing the same kind of slow generalist work for somewhere over a hundred and ten years.
In 1995, agricultural researchers studying free-range poultry as a pest control method in apple orchards in Connecticut, documented something that any rural homeowner with chickens already knew.
A hen with access to an infested orchard will eat Japanese beetles.
Not occasionally, not as a last resort, routinely, by the dozens, every single day during the adult beetle emergence in July.
The peer-reviewed study confirmed that Japanese beetles were significantly less abundant on apple trees in treatment plots where chickens were present, and that the chickens were both eating adult beetles falling from the trees and scratching up grubs in the soil during their normal foraging.
This is the part of the story that surprises nobody who has kept poultry. A backyard hen with five chickens in central Pennsylvania in early July is one of the most effective Japanese beetle adult stage controls available to a homeowner. She does not need to be trained. She does not need to be deployed. She walks the property. She eats what she finds.
But the hen, like the robin, is a generalist. She eats beetles when they are abundant. She does not target them.
Something else, smaller, working at the level of the beetle's body itself, does.
The Japanese tachinid fly, Istocheta aldrichii, small, gray, the size of a housefly, was introduced as a biological control between 1922 and 1933, and is now well established across the northeastern United States. It is not native.
It is, however, naturalized, settled into the food web for over 90 years now, behaving as if it were always part of The female fly is the part that matters.
She finds an adult Japanese beetle. She lands on its back. She lays a single egg, white and visible, between the beetle's wing covers.
Within 24 hours, the egg hatches. The fly maggot bores through the beetle's exoskeleton and into the body cavity, where it feeds, consuming the beetle from the inside, paralyzing it within days, killing it before it ever finishes laying its own eggs.
You can see them on infested rose bushes in the right week of July.
Living Japanese beetles with a single chalk white dot on the back of the thorax, slow moving, already doomed.
The hen on the ground, the fly on the back.
Two predators working two phases of the beetle's life. Neither one is native to North America.
Both have been doing what they do without further help from us for the better part of a century.
But the third layer, the deepest one, was here all along.
In 1988, a researcher in Connecticut was examining sick Japanese beetle grubs collected from a single field. Most of the grubs had died from causes that looked unusual under the microscope.
Their gut tissue was filled with tiny spore-like structures. What he had found was a microsporidian pathogen, a microscopic single-celled organism related to fungi that had been infecting Japanese beetle grubs in that one Connecticut field almost certainly for years without anyone looking for it.
The pathogen was given the name Ovavesicula popilliae. Translated loosely, the spore vesicle of Popillia, the genus name of the Japanese beetle.
Ovavesicula popilliae is, as far as researchers can determine, [music] native to North America. It did not arrive with the beetle. It had been part of the eastern soil community for an unknown number of years before it ever encountered a Japanese beetle grub and apparently decided that the grub was a viable host.
In the decades since 1988, Michigan State University researchers studying Ova vesicular popilliae have documented what it does to a Japanese beetle population.
The pathogen does not kill the grub outright. It slowly destroys its Malpighian tubules, the equivalent [music] of the kidneys, over a period of weeks.
The infected grub survives, but barely.
It eats less. It pupates slowly.
And critically, when the infected adult female finally emerges and tries to reproduce, her egg production is cut by roughly half.
The pathogen has now been released deliberately in five US states: Arkansas, Colorado, Kansas, Kentucky, and Michigan as part of a slow, careful introduction program.
Researchers have documented sustained suppression of Japanese beetle populations in study sites where the pathogen has established. It was already here.
It had been working on the beetle in at least one Connecticut field for an unknown number of years before anyone [music] noticed.
This completes the picture.
The birds on the surface eating adults and grubs. The flies on the back parasitizing the adult body.
The pathogen in the soil cutting the next generation in half before the eggs are ever laid.
Three layers of natural attrition.
None of them specialized. None of them complete.
All of them together doing more than any single pesticide product on the market.
This is what no eradication zone, no quarantine, and no spray program ever produced on its own.
It is what we kept walking past every spring, every fall for over a century.
The Japanese beetle is not going to disappear from North America. The studies are unanimous on that. The pesticide industry will not collapse next year.
The eradication zones in Oregon and California will continue to operate. The store shelves at the hardware store will keep their 15 brands of grub killer.
But somewhere underneath all of that, a different kind of control has been quietly working.
In peer-reviewed studies on real lawns, in real orchards, across the entire established range, a backyard with healthy populations of native birds, a few free-range hens if local ordinances allow, a soil community that has not been sterilized by repeated chemical treatments, and increasingly, as the deliberate releases continue, Ova vescicular popilliae in the ground beneath the lawn will hold a Japanese beetle population at densities that the same yard, fully chemically managed, often does not.
It is not zero. It is not magic.
>> [music] >> It is what an ecosystem actually does when allowed to do it.
There is a thing you can do on a July morning in Pennsylvania, or Ohio, or Indiana, or northern Virginia, or anywhere the Japanese beetle has been for the last 90 years.
You can stand in your yard before the heat of the day and watch what is already happening.
A starling working the lawn, head down, prying the turf open for grubs.
>> [music] >> A robin pulling something white out of the soil near the foundation.
A wren or a catbird in the rose bushes picking metallic green beetles off the foliage one at a time.
If you have chickens, they are doing the same thing on a larger scale. Almost certainly without you having asked them to.
Look closely at a beetle on the back of one of your roses.
If it is moving slowly and if there is a small white dot on the back of its thorax, you are looking at one that will not finish the week.
And in the soil under your feet, if it has not been chemically sterilized, the third predator, the one nobody told you was there, is doing its slow work on grubs you will never [music] see.
We have spent over two billion dollars a year, every year, for decades on the chemical side of this problem.
The birds, the fly, and the pathogen never sent us an invoice.
They just kept doing the work in plain sight while we kept looking past them.
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