In the American Southwest, where deer and coyotes roam free and the prickly pear cactus grows wild, there’s a new outsider ready to cause trouble. But there’s no need for sheriffs and masked vigilantes to be on the lookout for rogue cowboys galloping on horseback. And there’s a new hero on the scene: scientists. They must rise to the occasion. And quickly. Or else.
Or else South America’s Cactoblastis cactorum, an invasive cactus moth with a wingspan about the same size as the length of a standard paper clip, will devastate the Southwest’s prickly pear. The cactus, known for its flat pads and pear-shaped edible fruit, is the state cactus of Texas and a vital member of the ecosystem. It’s a source of food and shelter for mammals, birds, reptiles and insects; it acts as a nurse plant, providing a safe space for smaller plants to germinate and grow. The agricultural economy relies on prickly pear to feed cattle. Even Mexican cuisine depends on prickly pear to make nopales.
This cactus moth eats the prickly pear’s insides, causing the plants to collapse, and it has wiped out populations of the plant before. In the 1920s, Australians used the moth as a biological control when prickly pear took over the bushland. At the peak of the prickly pear infestation, there was as much as 60 million acres infected. In just a few years after the moth was introduced, the prickly pear became almost nonexistent. This success led to the moth being used across Caribbean islands for the same reason.
But in the late 1980s, the moth made its U.S. debut in the Florida Keys, causing widespread damage to the native North American plant and raising fears that the insects could move on to Texas and Mexico. Those areas have a high density of prickly pear and temperate weather, ideal conditions for the moth to spread. It’s the perfect recipe for disaster.
Since 2007, the scientists at Brackenridge Field Laboratory, including director Lawrence Gilbert and research scientist Rob Plowes, in partnership with scientists and labs in Florida, Mexico and Argentina, have been racing against the clock to prevent a repeat of what happened in Florida and Down Under.
“Our concerns were heightened,” Plowes says. “We actually took the initiative to do some preemptive work because we realized that …”
“… they were going to get here,” says Gilbert, a professor in the Department of Integrative Biology.
And they did. In 2017, there was an unconfirmed sighting of the cactus moth along the Texas coast. By December 2018, there were four recorded reports of the moth in the state. More have been sighted over the past year and as recently as early February. With little data, it’s hard to predict how quickly the cactus moth will spread. It might be helped inland by the Gulf breeze, but colder conditions could prevent a second generation of moths. Westward spread might be slower, but warmer weather gives the moth better chances of survival.
Plowes estimates that the moth could reach Mexico within three to five years, but the lab is continuously working to find the rate of spread so it may better alert people about potential damage.