Genetically Engineered Moths Could Eliminate Crop Pests

Published April 23, 2020

Diamondback moths can wipe out entire fields of crops and ruin farmers. They’re also the pests most resistant to insecticides and crops genetically modified to kill them. Farmers, however, might soon be getting a new weapon to combat them: genetically engineered versions of the moths that mate with wild pests and cause half their offspring to die—but that will happen only if federal regulators significantly speed up their approval process.

The biotechnology company Oxitec developed the modified diamondback moths, which survive well on actual farms. Once modified males mate with females in the wild, where their “lethality” gene is passed along, the gene prevents the female offspring from developing, so they die as larvae.

Meanwhile, the male offspring survive with half inheriting the “lethality” gene. The population shrinks further when those males grow up and mate with other wild females, causing the next generation of female offspring to die as well.

Resistant to Pesticides

The diamondback moth is the number one insect in the world for resistance to pesticides, says Alton Sparks, professor of entomology at The University of Georgia.

“Everything that has been tried to control diamondback moths, they have developed a resistance to,” said Sparks. “We have populations in south Georgia that we are unable to control with insecticides.”

Sparks says the pests are very particular about what they feed on: vegetables that thrive in cold or cool weather, such as broccoli, cabbage, canola, cauliflower, collards, and kale, resulting in billions of dollars in lost crops each year.

“They chew holes in the leaves while they’re a caterpillar,” Sparks said . “You can lose an entire field because they make the crops unmarketable.”


It will take a while for the technology to truly cut down diamondback moth populations, says Sparks.

“You can’t put the modified moths out there and then spray pesticides, because you might interfere with modified moths being released,” said Sparks. “There will be a learning curve, but it’s something we can establish as the population limits itself, and we will have to work with the population for a while before it overcomes the wild population and causes it to crash.”

The Oxitec technology is species-specific, so it will not impact non-target species, says Sparks.

“If it works the way we hope it will, then it replaces fairly heavy pesticide use,” Sparks said. “There may be some concerns because it involves genetic modification of the insect, but it is not something that’s going to end up contaminating or damaging the food supply or the environment, and the modification doesn’t affect other species.

“If this species becomes extinct, it would make crop production much easier and reduce chemical use,” said Sparks. “The diamondback moth is a worldwide pest. I’ve been studying it for the past 32 years, and it’s unfortunate this technology is years away from being commercially available,” because of the long delays awaiting approval by federal regulators.

‘An Unalloyed Good’

If the GMO diamondback moth works as designed, it would be a pure good for agriculture, the environment, and society, says Gregory Conko, a senior fellow at the Competitive Enterprise Institute.

“If successful, modified diamondback moths would represent an unalloyed good: a boon to farmers, food production, and the environment,” said Conko. “It is always good when farmers have another tool to help them fight pests, because globally it’s estimated they lose between 20 and 40 percent of their crop potential to pests.

“The number is closer to the lower end of the range in industrialized countries like the United States, but a technology like this can easily be used in other parts of the world, and no matter where you are, less crop loss to pests means more food, lower prices paid by consumers, and fewer resources needed to produce a given amount of food,” Conko said.

“In addition, although chemical spray insecticides can be used safely—meaning, with little risk to humans—and though they can be used in a way to minimize the impact on nature, a crop protection technology like this, narrowly targeted to impact only the pest species, is especially welcome because it will have very low risk of effects on non-target organisms, allowing farmers to control diamondback moths with essentially zero unintended side effects,” Conko said.

Regulations Likely to Slow Introduction

The biggest remaining hurdles to commercial introduction of the GMO moth are regulatory, says Conko.

“Theoretically, we could be relatively close to commercialization, because the genetically engineered moths have been studied over multiple generations in the closed environment of a greenhouse, with very promising results, and a recent field study [published in the journal Frontiers in Bioengineering and Biotechnology] showed positive results as well,” Conko said. “Naturally, you’d like to study the impacts in the field over a couple of additional years to make sure the technology works and lasts over the long run, and to ensure there are no unintended side effects, meaning under normal circumstances, the GMO diamondback moth could be ready for commercial release in three to four years, tops.

“The biggest hurdles to commercialization are not likely to be related to the technology working safely, but due to regulations, because even after extensive safety testing, federal regulators will likely take several additional years before making a decision as to whether the technology can be released commercially,” Conko warns. “As a result it would not be unrealistic to think it could take over a decade before the Oxitec’s modified moth reaches the marketplace.”

Kenneth Artz ([email protected]) writes from Dallas, Texas.