Scientists Track Beetles in Effort to Stop a Plant Plague

Rob Dunn is trying to prevent squash heart attacks.

Carried by the spotted cucumber beetle, a bacterial disease is giving squash, pumpkins, cucumbers and melons the botanical equivalent of clogged arteries. Wilting leaves are the first sign as the bacteria multiply in the plant’s circulatory system. The disease can nearly wipe out a farmer’s field.

“It’s a bad way to die,” Dunn said. “All your veins have been filled up with some bacteria.”

Dunn, an ecologist at North Carolina State University, said the way we farm today makes it easy for this and other plant plagues to spread.

Modern farms raise just a few crops over wide areas. While they feed more people more affordably than ever, there are risks in this way of feeding the world.

For a hungry pathogen, a giant monoculture is “the holy land, right? It’s unbelievable. You can eat from one end to the other,” Dunn said.

‘A story we repeat again and again’

The Irish potato famine of the 1840s is the worst-case scenario. About a million people died when a fungus wiped out the one crop on which most of the population subsisted.

That kind of catastrophe is rare. But Dunn says devastating disease outbreaks are an inevitable byproduct of modern agriculture.

“This is a story we repeat again and again,” he said.

Dunn tells several of those stories in his new book, Never Out of Season.

One example: Henry Ford’s rubber plantations. The auto pioneer planted millions of rubber trees on land carved out of the Brazilian Amazon in the 1930s. But pests and disease ravaged them again and again. Ford gave up in 1945. Fordlandia, as the first plantation was known, is now an abandoned ruin.

Then there’s the fungus that nearly wiped out cocoa production in Brazil, a suspected bioterrorist attack that wrecked the economy and transformed the ecosystem; and the cassava mealybug that threatened Africa in the 1980s.

Prepare now

Still, Dunn says he doesn’t expect agriculture to change anytime soon.

“People like cheap food,” he said. “We feed more people than we ever have.”

But, he added, we should be doing much more to prepare for the next inevitable plague.

That means collecting and preserving as many crop varieties as possible, plus their wild relatives. In addition, we need to know much more about the complex microbial ecosystem living in, on and around our crops.

“If there’s a fungus on which the roots of squash depend, we don’t know it. If there’s a fungus that grows inside the squash plant that helps it defend itself, we don’t know it. If there’s a parasite that attacks the beetle that carries the bacteria, probably nobody’s studying it,” Dunn said. “And that’s true for most of our crops.”

The Great Pumpkin Project

Dunn is working to fill in some of those gaps.

And he wants the public to help.

Scientists don’t know how far squash heart attack disease has spread, and they don’t know where the beetles that carry the disease are from year to year. So, scientists want anyone growing squash — or pumpkins, melons, cucumbers or any of the other members of the family — to watch out for them.

The Great Pumpkin Project at the citizen-science site iNaturalist.org is looking for pictures of attacking insects and sick plants.

Dunn hopes to collect millions of images from around the world, which would help scientists get a better sense of “which of these beetles is living in which places and eating what.”

And, hopefully, stay one step ahead of the next plant plague.

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