Scientists Try To Fight Crop Damage With An Invasive Moth's Own DNA
If you like coleslaw — or kimchi or sauerkraut on your hot dog — you should worry about cabbage. This staple veggie has been under constant threat for decades, along with broccoli, cauliflower, collard greens, Brussels sprouts, kale and other leafy greens belonging to the Brassica genus. The danger? A tiny insect called the diamondback moth, an invasive marauder that has spread across the world and mutated to become immune to each new chemical pesticide designed to slay it.
To curb the billions of dollars of damage caused by this lepidopteran's larvae every year, scientists in New York are trying to turn the critter's own DNA against it. In a small cabbage patch near the Seneca Lake town of Geneva, a Cornell University entomologist is letting loose thousands of genetically modified diamondbacks to test their ability to disrupt the moth-mating scene in farmers' fields. Each moth, bred in a laboratory, carries a deadly gene designed to kill offspring that inherit it. The toxic gene offers a biological alternative to the chemical warfare farmers have been waging for decades.
"In areas where we can't control diamondback moths, this technology would allow more of a steady flow of products onto the market," says Anthony Shelton, the Cornell entomologist testing the moths. Shelton conducted a preliminary field trial of the insect in outdoor cages two years ago.
But will these genetically modified moths, developed by the British biotech company Oxitec, also inherit the stigma of genetically modified crops — or of the genetically modified mosquitoes also made by Oxitec?
Many traditional farmers in New York, which produces more cabbage than any other state, are excited about the new tool. Anthony Piedmonte has grown cabbage for more than half a century in Holley. (He leaves a few heads on his Polish neighbor's doorstop each year, and she reciprocates by dropping off a pan of a delicious stuffed cabbage dish called gołąbki.) Some years he has more cabbage to give than others.
"I've had years in which this moth has consumed more than 25 percent of my crop," says Piedmonte. "This last year was particularly bad." When things get really out of hand, he says, his farm sprays a cocktail of chemicals up to three times a week.
Piedmonte is lucky. The cold winters of New York exterminate diamondback moths, which migrate up from the South each spring. In Southern states like Georgia — and in other countries with warmer climates — diamondback moths can multiply exponentially.
"The problem in the South is that we never get away from them," says David Riley, a vegetable entomologist at the University of Georgia — not connected to Oxitec's moth endeavor. "We have diamondbacks pretty much year-round, and if you start applying an insecticide, they will basically become immune to that insecticide in short order."
Organic farmers don't have the same problem, because they grow less and don't use the chemicals. "The diamondback moth is not a significant pest for me," says Andy Fellenz, an organic grower in New York. "The way I grow is different from the guy who grows a hundred acres of cabbage."
Fellenz says that he isn't against genetic modification, even though organic regulations prevent him from using modified insects. Data collected by Oxitec and reviewed by the U.S. Department of Agriculture (USDA) also suggest that the gene poses little risk to human health or the environment. But Fellenz worries that the insect research is running ahead of laws that would protect organic farmers from contamination. Legal precedent, focused on genetically modified crops, suggests that the organic certification of his land would not be endangered by wayward moths from a neighbor's farm. But the status of the produce itself is less clear, he says. The Northeast Organic Farmers Association, of which Fellenz is a staff member, has condemned the experimental release, calling for a "halt to any genetically modified organism."
"Organic vegetables are subject to spot checks for genetically engineered materials," says Fellenz. "Right now the onus is on the organic grower to do everything in their power to minimize the likelihood of contamination."
The USDA, in issuing a permit for the field trial of the new moths, did require traps to check for stray insects. But these traps are not designed to contain the insects, only to monitor them.
For scientists, releasing the altered insects in the out-of-doors is the next logical step in the long-running effort to curb insect pests that started after World War II. Millions of flies sterilized using radiation have been released to eradicate the screwworm, a parasite that fed on cows.
"If these new genetic interventions work, these moths should be more effective, since they aren't weakened by ionizing radiation," says Peter Atkinson, a geneticist at the University of California, Riverside.
The moth release is only small step forward, a test to see how well the males being set free survive and compete against wild males for mates. Their performance could determine whether these insects will eventually be coming to cabbage patch near you. "We have done multiple years of lab testing and testing in field cages, and everything indicates that these males can do a good job," says Neil Morrison, project leader at Oxitec. "But we need to see how they behave in more realistic circumstances."
Devin Powell is freelance science writer in New York whose work has appeared in the New York Times, the Washington Post, Nature, National Geographic, WIRED and many other publications.