In 1868, something was ravaging the vineyards of France. It was first officially noticed in 1866 in a village in the south of France. Winemakers couldn’t figure out what was happening, but noted that its symptoms reminded them of tuberculosis. It wasn’t a disease, but rather a bug: phylloxera, a tiny aphid. European Vitis vinifera vines first proved especially susceptible to the louse when French colonists in Florida tried and failed to cultivate them in the 1500s. Over the next few centuries, native American vines were imported to France, and phylloxera is thought to have jumped the Atlantic, unnoticed, in the 1850s. Over the next 15 years, the aphids destroyed nearly 40 percent of the vines in France. On July 15, 1868, a three-man commission set out to determine the cause of the blight.

“Suddenly under the magnifying lens of the instrument appeared an insect, a plant louse of yellowish color, tight on the wood, sucking the sap,” wrote botanist Jules Émile Planchon. “One looked more attentively; it is not one, it is not ten, but hundreds, thousands of the lice that one perceived, all in various stages of development. They are everywhere.”

Phylloxera causes grapevines to rot from the inside within three years, but at first, Planchon and his colleagues believed the tiny yellow bugs on the roots were simply a symptom. Desperate for help, their inaccurate findings were published immediately. “The phylloxera, a true gourmet, finds out the best vineyards and attaches itself to the best wines,” joked a British cartoon in 1890, depicting a well-dressed aphid gorging himself on French wine.

Back in Missouri, Charles Valentine Riley, Missouri’s state entomologist, immediately recognized Planchon’s description. Riley wrote to him in 1870, but was dismissed. In Missouri, he had observed phylloxera on the leaves of vines, not the roots. After much discussion, though, Riley prevailed. He visited Planchon in 1871 to take a look at the phylloxera there himself; it was indeed the same bug. Riley, a student of Darwin, was confident that American vines were resistant to the louse because the two species had evolved together. He was right.

By the winter of 1872, George Husmann of Hermann, along with St. Louis firm Bush and Sons and Meissner, sent nearly 400,000 vine cuttings to Montpellier, France. Despite some French resistance to using American rootstock, the project took off, and the so-called la défense began. Riley hosted Planchon in Hermann and St. Louis in 1873, and taught him how to grow phylloxera-resistant rootstock.

Husmann had done work on phylloxera with Riley, and later worked to save Vitis vinifera in California. “I put an exactly fitting graft of two eyes on the cuttings, having them first shortened for the uppermost knot, and winding around it, all along the graft-cut, a suitable twine,” he wrote in American Grape Growing and Wine Making. “In this wise one can finish about 175 grafts in a day, sitting snugly at home... I have not heard any complaints from France.”

Today, with few exceptions, all vines are planted with grafted rootstock in order to resist phylloxera, thanks to Missouri.