Murder Hornets Are Scary. But Pesticides Are Scarier.

While everyone is freaking out about invasive hornets, the largest threats to America’s pollinators remain unchanged.
Asian giant hornets attack a beehive

Satoshi Kuribayashi/Minden Pictures

Google the term murder hornet, and you might just think the apocalypse is at hand.

“Monstrous ‘murder hornets’ have reached the U.S.,” reports LiveScience. “The ‘murder hornet’ is as bad as it sounds,” opines Quartz. “A ‘murder hornet’ kills a man in Spain,” writes MarketWatch. “ ‘Murder hornets’…could decimate the honeybee population,” warns CBS News.

Yikes, right?

Well, I have some good news, some bad news, and some worse news.

The good news is that murder hornets aren’t new—they’re just new to us. So far, just one hive has been found in North America, on Canada’s Vancouver Island, and there have been two individual hornets discovered across the way in a suburb in Washington State. More officially known as Asian giant hornets, these wasps have been around for a long time, as in millennia, and they only kill people who happen to be allergic to their venom. So while the menacing-looking bugs clock in at about two inches in length with stingers that pack an extra painful punch, they aren’t any more likely to murder you than any other wasp. 

The bad news is Asian giant hornets do happen to be quite good at butchering smaller insects, such as honeybees. They’re carnivores, after all. And if the species were to establish itself in the United States, the so-called murder hornet could inflict a pretty nasty impact on all sorts of pollinators.

Worse still, invasive hornets are just another threat in a long list of things killing off honeybees and native pollinators these days.

“There's climate change. There's habitat loss. There are pathogens and parasites,” says Dan Raichel, a staff attorney at NRDC who specializes in pollinators. But, according to Raichel, one threat rises above the rest: pesticides. 

Pesticide being applied to strawberry plants

David Gomez/iStock

About 25 years ago, the use of a family of pesticides called neonicotinoids, or neonics, started to take off. Unlike sprays and powders, neonics are a type of systemic pesticide, meaning that a small amount can be applied to a seed before it’s planted and, as the plant grows, it soaks up those poisons into all of its tissues. This makes the whole plant, from root to stem, toxic to insects, which has enabled farmers to protect their crops like never before. But the same technology has also made agriculture 48 times more toxic to insects (pests and non-pests alike) than it was a quarter century ago.

Part of the reason why is because crops only use some of the pesticides within their seeds, which leads to plenty more of the chemicals winding up in the soil. And when it rains, that nasty stuff gets around. “If it encounters wildflowers, then those wildflowers are sucking up the pesticide. Their pollen and nectar become toxic to insects,” says Raichel. “The coating on a single corn seed can kill up to a quarter million bees or more.” And while the honeybees may keep their heads, a death via pesticide is gruesomely slow and painful.

From fertilizers to miticides for beekeeping to tick and flea treatments for pets and livestock, pesticides are literally everywhere, and they can have sublethal effects on insects too. In a study published this February in the journal Behavioral Ecology and Sociobiology, scientists showed that exposure to miticides and pesticides slowed down egg-laying rates in queen bees, resulting in about half as many worker bees produced over the queen’s one- to two-year life span.

The queens were alive, but they weren’t thriving. That’s not all.

“When the drones came out, they took longer to mature than normal,” says Juliana Rangel, a behavioral ecologist at Texas A&M University and senior author of the study. “When they reach sexual maturity, fewer drones were able to produce sperm. And those that did had a significantly lower viability of the sperm.”

Weirder still, pesticide exposure changed the way the queens smelled.

A queen emits pheromones out of glands on her face, says Rangel, and these stimulate her entourage of workers—officially called a retinue—to feed and groom her. But something changed in the chemicals emitted by queens that had been exposed to pesticides. And as a result, the retinue started to slack in their duties, which likely triggered the drop in productivity from the royal majesties.

Western honeybees

Thomas Hawk via Flickr

And what about “murder hornets”? “For now, we just have to focus more on the other pressing issues of bee and pollinator health,” she says.

Still, it makes sense to be uneasy about Asian giant hornets, especially once you’ve watched the marauders shear off the heads of a few hundred honeybees using nothing more than their mandibles. But with states in the Pacific Northwest already on high alert looking for more evidence of an invasion, Rangel says the rest of the country doesn’t need to worry about a “murder hornet” takeover just yet.

In fact, many places in the United States may have an ace up their sleeve in the form of invasive Chinese mantises. That’s right, murder hornets have predators, and, for better or worse, some of them may already be in your backyard.

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