nature.org: Assuming the moth jumps from Isla Mujeres to the Mexican mainland, how long would it take to have a big impact on Mexico’s biodiversity and its economy?

John Randall: If it advances as quickly as it has in Florida, within a matter of years it’s likely to be in the Mexican desert ecosystems — both the Sonoran and the Chihuahuan. Mexico has 76 types of flat-bladed Opuntia (the group of prickly pear cactuses that the moth attacks), and 38 of them are found only in Mexico. So Mexico is really a center for prickly pear cactuses.

The cactus is also important agriculturally and symbolically to Mexico — it’s on the Mexican flag, where an eagle is depicted perched on a prickly pear cactus.

nature.org: What’s the Mexican government doing to stem the infestation on Isla Mujeres?

John Randall: They’re doing control operations — which means either cutting and burning the pads that are infested, killing whole infected plants and destroying them, or treating the plants with insecticide. In addition, they’re doing surveys on the mainland of the Yucatan Peninsula to determine if any have spread there. Thus far, they have not found any moths in the wild. They have found some in shipments into the country.

nature.org: What’s the Conservancy doing to address the invasion?

John Randall: The Conservancy has been involved for several years in trying to promote implementation of the USDA's sterile-male-release technique or other ways of stopping the advance of the moths, particularly to the west but also to the north. We’ve also helped sound the alarm about the problem and sought funds for control and prevention. And we're educating people to keep their eyes out for it and to discourage the movement of material that might be affected.

In Mexico, the Conservancy was trying to get more government attention and money to the problem before the discovery on Isla Mujeres was even made. The Mexican government has actually put money into the U.S. effort to prevent the moth from moving across the Mississippi River. They were actually giving the USDA money for the sterile moth release, and our folks were promoting that.

In the United States, we’ve been involved since at least 2001 on the policy side to promote full-scale implementation of a sterile-male-release technique. There has been research on the sterile-moth technique, and then a pilot was held back due to lack of funding. We believe it’s a very high priority.

nature.org: How does the sterile-male-release technique work?

John Randall: Essentially what you’re doing is flooding the mating market. The sterile males mate with females — and if there’s enough sterile males, they reduce the numbers of successful matings to a very low level.

The technique is the best thing we have right now. There’s been research into a biocontrol agent, but one hasn’t been found that would reduce or drive down the cactus moth populations to acceptable levels without harming native species of moths. And we found in Florida that putting cages around the cactuses was a problem because they prevented the pollinators from reaching the flowers. So that’s not a permanent solution.

nature.org: The moth is already in Florida and other Gulf U.S states. What should the United States be doing to stop the moth from spreading to the U.S. Southwest?

John Randall: We should be fully funding the sterile moth program. We should also be fully funding the cactus moth detection and monitoring network at Mississippi State University. And also funding the Mexican program to eradicate the moth on Isla Mujeres and prevent it from moving to mainland — because if they get it and the pincer arm moves up from the south, we’re going to get it anyway. The Mexicans were very farsighted in working with us to prevent the problem from getting to them — it would be wise for us to do the same.

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