Genetically Modified Moths Come to New York

A diamondback moth with altered DNA is being tested to control pests on cabbages.

Brown moth on green leaf
A wild diamondback moth in Germany (Olaf Leillinger / Creative Commons)

Earlier this spring, Anthony Shelton found himself planting a cabbage patch with members of his lab in upstate New York.

“We’re A to Z here,” says Shelton, who is an entomologist at Cornell University. If “A” is planting cabbages, then “Z” is releasing into that cabbage patch insects genetically engineered to breed themselves out of existence—the first time such insects have ever been released in the United States. If the experiment works, it could herald a new era for pest control.

The insects in this case are diamondback moths, notorious among farmers as pests that cause $4 to $5 billion of damage a year worldwide. The moth especially likes to munch on Brassica plants, which include cabbages, cauliflower, and broccoli. And it has become increasingly resistant to available insecticides. So Shelton’s cabbage patch in Geneva, New York, is the site of a long-awaited field test to see if genetic engineering could control the diamondback moths. The test began in August and will run until the cold starts killing the moths off.

The moths themselves were engineered by Oxitec, the company perhaps best known for its genetically engineered mosquitoes: Male mosquitos carrying a lethal gene are released to mate with wild females, and their offspring die before reaching adulthood. Oxitec has carried out field trials of mosquitoes in Brazil, Malaysia, Panama, and the Cayman Islands, aiming to eventually mitigate mosquito-borne diseases like Zika, dengue, and yellow fever. A planned U.S. trial in the Florida Keys, however, has moved slowly because of local pushback.

Like Oxitec’s mosquitoes, its diamondback moths are genetically engineered to be self-limiting. Shelton is releasing males carrying a lethal gene that eventually kills all female offspring. Over time, the males will have no one to mate with.

The diamondback-moth release, too, has its critics. The U.S. Department Agriculture’s decision to allow the field trial got hundreds of comments, many of them brief but angry. “DO NOT PERMIT! Future ramifications are unknown and could be dangerous to the entire world,” reads a typical comment. The Northeast Organic Farming Association of New York also criticized the decision due to fears of the genetically engineered moth spreading to their organic crops.

For the scientists, however, this field test is the next logical step after experiments in greenhouses and field cages. Shelton says it’s unlikely the moths will spread because of the remote location of the cabbage plot. Still, he’s installed traps to track how far the engineered moths can fly.

“Undoubtedly this has been the most—how should I say it—paper-intense project that I’ve ever undertaken,” says Shelton, who first heard about Oxitec’s genetically engineered insects about eight years ago. He says he’s been extra careful because of the scrutiny that comes with the first U.S. release of genetically engineered self-limiting insects. “Scientists want to be the first to do something,” says Shelton. “In this particular case, I would have loved to be the second.”

There is precedent, of a sort, for releasing sterile insects for pest control. From the 1950s to the early 2000s, a massive effort went into eradicating invasive screwworms—which burrow into the flesh of livestock—from the United States down to Panama. That campaign used screwworms raised in a factory and bombarded with radiation, which damaged their DNA so much as to make them sterile.

Then, beginning in 2006, researchers tested irradiated and sterile pink bollworms—also from Oxitec—in cotton fields in Arizona. These bollworms had been genetically modified to carry a fluorescent protein, which marked them as the company’s. That was the first release of insects with any sort of genetic modification in the United State. The general sterilization-by-irradiation strategy has also been used to control the Mediterranean fruit fly and the Mexican fruit fly.

The diamondback moths are not irradiated, though, because the irradiation strategy didn’t work. Shelton tried that back in the 1990s. “You could sterilize them, but they were not very fit. They couldn’t fly,” he says. The radiation had damaged them too much. Genetic engineering is a more precise way make the moths unable to viable offspring, leaving them still fit enough to fly and mate.

Scientists are watching the diamondback moth trial closely. “I’ll be very interested to see if this thing succeeds,” says Fred Gould, an entomologist at North Carolina State University. In addition to diamondback moths and mosquitoes, Oxitec has a handful of other genetically engineered insects that can be used to tackle common pests: the Mediterranean fruit fly, the Mexican fruit fly, and the olive fly.

Whether genetically engineered insects can succeed as pest control may be location-specific. In upstate New York, diamondback moths die in the cold winters and others migrate up from the south in the spring. That means there are relatively few moths to deal with in the spring each year. The bigger the natural moth population, the more genetically engineered ones you have to release to be effective. In places where diamondback moths can live year-round, like India, their populations are much, much higher. “To think of it as a cure-all ... that’s asking a lot,” says Gould. Screwworm eradication in the 20th century worked in part because its populations were relatively low despite causing a lot of damage.

Then there is the local community and how it views the release of millions of genetically engineered insects. In Brazil, says Sarah Hoey, an Oxitec spokesperson, mosquito-borne diseases are more pervasive than in Florida: “For want of a better phrase, they’re almost less desperate to have a solution [in Florida]. Whereas in Brazil, they’re really desperate for someone to help. It depends on the community you’re dealing with at the time.”

With agricultural pests, the dynamics of winning the public over may be a little different. Do you just need to convince the local farmers, or do you need to convince everyone who buys cabbage? Shelton has spoken at two local forums in upstate New York and says they went fairly well. “We have a lot of farming community around, and people are quite proud to live in an area where they know the farmers, so it’s not like doing something in downtown New York City,” he says. One New York farmer told Scientific American, “I think using the insects is an awesome idea.” But what will that cabbage buyer in New York City think of genetically modified insects flitting around their vegetables? And should it be any different than irradiated fruit flies, which are routinely used to control pests on produce?

The fervor of the anti-GMO movement is often traced to Monsanto’s initial mistake decades ago in creating traits like innate insecticides that helped farmers, but whose benefits to the consumer were unclear. Public opinion about genetically engineered insects is still in the formative phase. Whatever happens, it will have all started with this cabbage patch in Geneva, New York.