A BRITISH BIOTECH firm that developed a genetically modified mosquito to fight dengue fever and other blood-borne diseases in Florida and Texas now has introduced a self-destructing GM caterpillar. Their aim is to stop a pest that is devastating corn and rice crops across the globe.
Executives from the US-owned, but UK-based, firm Oxitec and its multinational partner Bayer announced today that they have developed a fall armyworm that has a self-limiting gene introduced into the male of the species. Once the male mates with a female, the resulting egg becomes overloaded with a key protein and quickly dies. “Our gene produces this protein at such high levels that other natural proteins that are important for the caterpillar’s development can’t be produced,” says Neil Morrison, head of agricultural programs at Oxitec. “The normal cell machinery is swamped by the overproduction of this protein.” The company’s goal is to reduce the population of this kind of worm without pesticides.
Oxitec has already begun small field trials in Brazil of this trademarked “friendly” fall armyworm, according to Morrison, and it hopes to expand the size of the trials there in 2021 upon approval of Brazilian regulators.
Unlike so-called “gene drive” technology, in which a lethal gene is passed on throughout a targeted insect species ad infinitum, Morrison says the protein the Oxitec gene encodes for only affects the female. That means the lethal effect will last only a few generations. That built-in obsolescence could help allay concerns that a runaway genetic mutation could potentially destroy an entire species. That’s a scenario raised by people who have opposed using such a technology to eliminate the mosquito species that carries malaria.
From its origins in the Americas, the fall armyworm has munched its way around the globe in the past few years, leaving a trail of destruction and ruined crops. After the caterpillar moth landed in West Africa in 2016, it spread quickly throughout 12 nations and caused an estimated $6.3 billion in damage, according to a report by the UN’s Food and Agriculture Organization. An estimated 17.7 million tons of corn crops are eaten by the fall armyworm each year, the report concluded.
Since 2016, the growing infestation of fall armyworms across Africa has forced growers in many developing countries to start spraying pesticides, which normally aren’t used by small-scale African farmers and can damage both human health and the environment. In 2017 the Zambian government gave $3 million to small farmers to fight the fall armyworm with agricultural pesticides, and replanted 222,000 acres of damaged crops. That year in Rwanda, troops were deployed to farmers’ fields to crush the insect egg masses by hand, the FAO report stated. From Africa, the armyworm has since invaded 44 countries and found an appetite for more than 80 different crops including rice, sorghum, wheat, and cotton, according to this report by the UK-based nonprofit Center for Agriculture and Bioscience International.
In North America, the fall armyworm leaves the southern tips of Florida and Texas each spring to spread all the way to Canada, destroying corn, rice, and sorghum fields. It usually doesn’t survive winters, according to Ashley Tesselow, an entomology graduate student at Texas A&M University who is researching control measures for the caterpillar. “Sometimes the fall armyworm population size skyrockets, causing an outbreak,” Tessnow wrote in an email to WIRED. “When this happens, there are so many fall armyworms that entire fields can be destroyed in just a matter of days if not controlled. These ‘Armageddon-like’ outbreaks do not occur every year, but they can result in complete yield loss.”
Tessnow says it’s important to know more about the genetic structure of the fall armyworm, a project she’s working on during her doctoral thesis. “It will be interesting to see how effective Oxitec’s release of GM fall armyworms is on reducing this insect’s population,” she writes.
Oxitec has some experience with producing genetically modified insects. The company began developing a GM mosquito, originally using gene drive technology, back in 2009 to control Zika, a virus passed through mosquito bites, which can cause birth defects in children developing in utero. Oxitec researchers then developed a second-generation mosquito with the self-limiting lethal gene that would only last for a few generations. That mosquito was approved by the Environmental Protection Agency for release this year in the Florida Keys, despite opposition from some environmental groups and local residents, who argued that the agency hadn’t fully considered the effects on human health and the environment.
After its approval by EPA regulators, Oxitec CEO Grey Frandsen said that using the GM mosquito would be both safer and cheaper than spraying chemicals to kill immature mosquitoes that can transmit dengue fever, Zika, and other blood-borne diseases. “Our aim is to empower governments and communities of all sizes to effectively and sustainably control these disease-spreading mosquitoes without harmful impact on the environment and without complex, costly operations,” Frandsen stated in a press release issued in May. “The potential for our technology to do so is unmatched, and this EPA approval will allow us to take the first steps towards making it available in the US.”
Oxitec also developed a genetically modified diamondback moth and did field trials in upstate New York in 2017 that used similar self-limiting genetic modification technology to reduce the population of a caterpillar that eats cruciferous crops like cabbage, cauliflower, and broccoli. That project was completed, and showed promising results, but the company decided to switch to the fall armyworm, Morrison says.
Still, not everyone believes introducing a modified insect is the way to combat agricultural pests. One skeptic is Jaydee Hanson, policy director at the Center for Food Safety, a Washington-based advocacy group that previously opposed the EPA’s decision to release Oxitec’s modified mosquito. After all, Hanson says, the Oxitec program would only kill one of many insects faced by farmers in the developing world, leaving the others to move in. “The problem is when you take a .22 rifle approach and what you need is something that will kill off, in a sustainable way, the other pests,” he says.
Anthony Shelton, a professor of entomology at Cornell University, worked with Oxitec on the experimental release of the diamondback moth in 2017. He agrees that the battle between farmers and pests can resemble an endless treadmill of technological innovation by scientists, immediately countered by fast-breeding insects who evolve to avoid what science throws at them, such as by developing resistance to pesticides. “We constantly have to modify our strategies, because it’s a biological system,” Shelton says. “What we need to do is find strategies that are more durable and more environmentally friendly.”
Both Shelton and Tessnow say that any genetically modified organism must be part of a system called integrated pest management, which includes rotating crops to stymie any buildup of insects on one particular plant, encouraging the growth of the pest’s natural predators, and using limited amounts of pesticides so insects that survive the chemicals don’t get a chance to build up resistance to them.
There’s a lot riding on the potential success of a chemical-free solution to the fall armyworm explosion that has shuttered farms across the world’s tropical zones. “This is a really serious global pest,” Shelton says. “We need to look at all the technologies to figure out what will work so we don’t have this catastrophe in agriculture.”