1493: Uncovering the New World Columbus Created (39 page)

“WAR UPON THE BEETLES”

In August 1861 beetles invaded a ten-acre garden in northeastern Kansas that belonged to a potato farmer named Thomas Murphy. His name was appropriate: Murphy, a common Irish surname, was also a slang term for potatoes. Murphy’s potatoes—Murphy’s Murphys—were overrun by so many beetles that he could barely see the leaves through the swarm of tiny glittering bodies. He knocked the insects from the plants into a basket, he wrote later, and “in a very short time gathered as many as two bushels of them”—remarkable, given that each insect was barely a third of an inch long. In a different context, perhaps, Murphy might have thought the beetle was beautiful, with its yellow-orange body and its forewings marked tigerishly with thin black stripes. But they were devouring his potato plants as fast as they came up.

Murphy had never seen the beetle before its hordes suddenly attacked his potatoes. Nor had his neighbors who also were visited by it, or the farmers in Iowa and Nebraska whom it invaded that summer. The insect marched steadily north and east, expanding its range by fifty to a hundred miles a year, shocking potato growers at every step. It reached Illinois and Wisconsin in 1864; Michigan, by 1870. Seven years later it was attacking potatoes from Maine to North Carolina. The little insects swarmed potato fields in such profusion, according to one widely repeated story, that they stopped nearby trains. Their bodies covered the tracks in a layer deep enough to make the wheels slip “as if oiled, so that the locomotive was powerless to draw the train of cars.” Strong winds blew the beetles into the sea, from which they washed ashore in a glittering, yellow-orange carpet that fouled beaches from New Jersey to New Hampshire. Farmers had no idea where the creature had come from or how to stop it from eating their potato fields to the ground.

The Great Hunger still a vivid memory, Europeans cringed to hear the reports of potato devastation. Companies produced thousands of small insect models to help farmers identify Murphy’s beetle. Germany imposed what may have been the world’s first-ever agricultural quarantine, against U.S. potatoes, in 1870; France, Russia, Spain, and the Netherlands followed suit. Great Britain, which had the most to fear, did not ban U.S. potatoes—it didn’t want to set off a trade war. Traveling in ship holds, the beetle kept appearing in European fields, only to be expunged. The First World War distracted governments from the task of monitoring insect movements. Seizing the moment, the beetle established a beachhead in France, then swept west. Today it occupies a swath of Europe that reaches from Athens to Stockholm. In the Americas its realm extends from south-central Mexico to north-central Canada. Many biologists fear that it will spread into East and South Asia, completing a round-the-world journey.

Murphy’s beetle is known to entomologists as
Leptinotarsa decemlineata
and to gardeners as the Colorado potato beetle. It is not from Colorado. Nor at first did it have any interest in potatoes. It originated in south-central Mexico, where its diet centered on buffalo bur (
Solanum rostratum
), a weedy, knee-high potato relative with leaves that somewhat resemble oak leaves. From the human point of view, the plant is annoyingly spiny, with barbed seedpods that stick in hair and clothes and are hard to remove without gloves. Biologists believe that buffalo bur was confined to Mexico until Spaniards, agents of the Columbian Exchange, carried horses and cows to the Americas. Quickly realizing the usefulness of these foreign mammals, Indians stole as many as they could, sending them north for their families to ride and eat. Buffalo bur apparently came along, tangled in horse manes, cow tails, and native saddlebags. The beetle followed in its path, hopping along a chain of corrals and stock pens. After arriving in Texas, the bur also could have been carried by bison, which migrate from south to north in the spring. By 1819 the beetle had arrived in the Middle West, where a naturalist observed it feeding on buffalo bur along the Missouri River. In this area it first encountered the cultivated potato.

Chance intervened. In Mexico the beetle, specialized on buffalo bur, finds it easy to ignore the delights of
S. tuberosum;
placed on a potato leaf, it will seek sustenance elsewhere. But one midwestern beetle in the mid-nineteenth century was born with a tiny mutation—perhaps, according to one suggestive study, a slight shift at a particular spot in its second pair of chromosomes, a snippet of DNA that flipped end to end. The mutation was not enough to make the beetle look different or affect its ability to reproduce. But it may have been enough to widen its focus from buffalo bur to a relative, the potato.

“The progeny of one pair, if unmolested for a year, would amount in the aggregate to over 60,000,000 of individuals,” the
New York Times
calculated in 1875. The actual figure is more like sixteen million, but the point is valid—a single genetic accident in a single individual was enough to generate a worldwide problem. The beetle is the potato’s most devastating pest to this day. “One of the worst features of the present visitation,” the newspaper continued, “is that the Colorado beetle is noted for its permanency, and rarely abandons localities until it has ravaged them for several seasons in succession.… Under such circumstances, the only resource is to commence an aggressive war upon the beetles.”

War with what weapon? Farmers tried everything they could think of: picking off and crushing beetles with special pincers; trying to find less-attractive potato varieties; encouraging the insect’s natural predators (ladybirds, soldier beetles, certain species of tiger beetle); moving potato fields every season, thus avoiding beetles overwintering (an insect version of hibernation) in the soil; surrounding their plots with buffalo bur, “so as to concentrate the insects, and thus more readily destroy them”—here I am quoting Charles Valentine Riley, founder and longtime head of the U.S. Entomological Commission. An Iowa man touted his horse-drawn beetle remover, which raked the insects into a box dragged behind. Potato growers doused plants with lime, sprinkled sulfur, spread ashes, sprayed with tobacco juice. They mixed coal tar with water and splashed that on the beetles. Some farmers reportedly tried wine. Others tried kerosene. Nothing worked.

Insects have bothered farmers since the first planting of crops in the Neolithic era. But large-scale industrial agriculture changed the incentives, so to speak. For millennia the potato beetle had made do with the buffalo bur scattered through the Mexican hills. By comparison, an Iowa potato farm—hundreds of orderly rows of a single type of a single species—was an ocean of breakfast. By adapting to the potato, the beetle could command many more resources for reproduction than it had ever possessed before; its numbers naturally exploded. So did those of other pests—the potato blight is a notable example—that were able to take advantage of the same opportunities. Each of the massive new farms was a fabulous storehouse of riches for the species that could exploit it.

Those farms were ever more similar, a hallmark of the Homogenocene. Because growers planted just a few varieties of a single species, pests had a narrower range of natural defenses to overcome. If a species was able to adapt to the potatoes in one place, it would not have to adapt to those in others. It could simply jump from one identical food pool to the next—a task that was easier than ever, thanks to modern inventions like railroads, steamships, and refrigeration. Not only did industrial agriculture present insects with a series of rich, identical targets; these faster, denser transportation networks made it ever easier for faraway species to exploit them. In 1898, L. O. Howard, Riley’s successor, calculated that at least thirty-seven of the seventy worst insect pests in the United States were recent imports (he wasn’t sure of the origins of six others).

As this cover illustration on an 1877 number of the London newspaper supplement
Funny Folks
suggests, British farmers feared the arrival of the Colorado potato beetle. (
Photo credit 6.7
)

The late nineteenth century was, in consequence, a time of insect plagues. The boll weevil, slipping over the border from Mexico, wiped out so much cotton in the South that the governor of South Carolina proclaimed a day of public prayer and fasting to fight the bug. The cottony cushion scale, an Australian insect, swept through California’s citrus industry. A European import, the elm leaf beetle, ravaged elm trees in U.S. cities; Dutch elm disease, introduced from Asia despite the name, would arrive later and more or less wipe out all elms east of the Mississippi. Returning the favor, the United States exported phylloxera, an aphid that wrecked vineyards in most of France and Italy.

For the wine industry, the solution was discovered by Riley, the Entomological Commission head: grafting European grape vines onto U.S. grape roots, which resist the aphid. For decades afterward, most French and many Italian grapevines had American roots. For the potato, the solution was more consequential: Paris Green.

Paris Green’s insecticidal properties were supposedly discovered by a farmer who finished painting his shutters and in a fit of annoyance threw the remaining paint on his beetle-infested potato plants. The emerald pigment in the paint was Paris Green, made largely from arsenic and copper. Developed in the late eighteenth century, it was common in paints, fabrics, and wallpaper. Farmers diluted it heavily with flour and dusted it on their potatoes or mixed it with lots of water and sprayed.

Paris Green was a simple, reliable solution: buy the pigment, mix in flour or water according to the manufacturer’s instructions, apply it with a sprinkler or dust box, and watch potato beetles die. To potato farmers, Paris Green was a godsend. To the nascent chemical industry, it was something that could be tinkered with and extended and improved. If arsenic killed potato beetles, why not try it on other pests? Why not spray Paris Green to combat cotton worm, apple cankerworm, apple codling moth, elm leaf beetle, juniper webworm, and that plague of blueberries, the northern walkingstick? Arsenic killed them all. It was a godsend to cotton farmers reeling from the boll weevil. Eager scientists and engineers invented foggers and pumpers, sprayers and dusters, pressure valves and adjustable brass nozzles. The dust changed to liquid; the copper-arsenic mix changed to a lead-arsenic mix and then a calcium-arsenic mix.

If Paris Green worked, why not market another arsenic-containing pigment, London Purple? Why not other chemicals for other agricultural problems? In the mid-1880s a French researcher discovered that the “Bordeaux mixture”—copper sulfate, used to keep children from eating fruit—would kill downy mildew on grapevines. Given a new chemical weapon, researchers pointed it at other pests and hoped it would prove as deadly as Paris Green. Quickly they found that copper sulfate was—oh, happy day!—the long-sought remedy for potato blight. Spraying potatoes with Paris Green, then copper sulfate, would eliminate both the beetle and the blight.

From the beginning, farmers knew that Paris Green and copper sulfate were toxic. Even before the discovery of its insecticidal properties, many people had got sick from living in homes with wallpaper printed with Paris Green. The thought of spraying food with this poison made farmers anxious. They dreaded the prospect of letting pesticides and fungicides build up in the soil. They worried about exposing themselves and their workers to dangerous chemicals. They were alarmed by the cost of all the technology. All of these fears came true, but all could be adjusted for, at least in part. For a long time, farmers didn’t know about the most worrisome issue of all: inevitably, the chemicals would stop working.

Colorado potato beetles are, genetically speaking, unusually diverse, which means that they have an unusually wide range of resources in their DNA. (In technical language, beetle populations have high heterozygosity.) Confronted with new circumstances, they adapt quickly. To farmers’ misfortune, these new circumstances included pesticides. As early as 1912 a few beetles showed signs of immunity to Paris Green. Farmers didn’t notice, though, because the pesticide industry kept coming up with new arsenic compounds that kept killing potato beetles. By the 1940s growers on Long Island found themselves having to use ever-greater quantities of the newest arsenic variant, calcium arsenate, to maintain their fields. Luckily for them, Swiss farmers spent the Second World War testing an entirely new type of pesticide on the potato beetle: DDT, a chemical bug killer with unprecedented range and sweep. Farmers bought DDT and exulted as insects vanished from their fields. The celebration lasted about seven years. The beetle adapted. Potato growers demanded new chemicals. The industry provided dieldrin. It lasted about three years. By the mid-1980s, each new pesticide in the eastern United States was good for about a season.

In what critics call the “toxic treadmill,” potato farmers now treat their crops a dozen or more times a season with an ever-changing cavalcade of deadly substances. Many writers have decried this, perhaps none more elegantly than Michael Pollan in
The Botany of Desire.
As Pollan observed, large-scale potato farmers now douse their land with so many fumigants, fungicides, herbicides, and insecticides that they create what are known, euphemistically, as “clean fields”—swept free of life, except for potato plants. (In addition, the crops are sprayed with artificial fertilizer, usually once a week during growing season.) If rain doesn’t fall for a few days, the powders and solutions can build up on the surface of the soil, creating a residue that resembles the aftermath of a chemical-warfare test. In my area, the Northeast, I have met farmers who claimed not to allow their children to walk around their fields. One doesn’t have to be an organic fanatic to wonder about the prospects of a system that turns the production of food into a toxic act.