Erythroxylum coca has pretty flowers but can be transformed into cocaine. Image credit: H. Zell, Wikimedia Commons // CC BY-SA 3.0

Earlier this month, a little moth called Eloria noyesi became a minor celebrity when it was proposed as Colombia’s latest weapon in its war on illegal coca crops. The government recently banned the use of the controversial herbicide glyphosate, which the World Health Organization now labels as a probable carcinogen.

The problem is, the herbicide has played a major role in reducing the amount of cocaine being produced in the country, which is at its lowest level since 1996. Cocaine was a primary fueler of the decades-long conflict that killed tens of thousands of Colombians—and it still plays a big role in the global drug market.

Could this moth be a safe biological alternative?

The plan seems simple enough: E. noyesi, also known as the cocaine tussock moth, lays its eggs on coca leaves. Five days later, hungry little caterpillars hatch and begin munching away on the leaves. Put enough of these caterpillars in a field of illicit coca and they’ll destroy the entire crop in no time. Even better, they only eat the two species of coca used to make cocaine.

At least, that’s what scientists believe. But let's not release the moths just yet—this is is uncharted territory. Although the moth, like coca, is native to the region, no one has ever released thousands of the little critters in the Amazon basin or coastal rainforest where the majority of Colombian coca crops are grown.

Before releasing the cocaine moths, scientists must be certain the caterpillars won’t eat any of the 155 other coca species—or any other plants. Given that relatives of the moth are known to feast on several other plant families, any plan to release large numbers of cocaine tussock moths should proceed very carefully, cautions Annette Aiello, a staff scientist with the Smithsonian Tropical Research Institute in Panama.

"You could lose plant diversity, as well as potentially cause serious damage to an ecosystem," Aiello says.

To guard against that, scientists will first study the moths in a laboratory, observing their development and tempting their offspring with a menu of plants that grow in the planned release areas. Once they’re satisfied the caterpillars only have a taste for the two coca species used in cocaine production, they’ll test these natural drug fighters in the field, carefully monitoring the moth’s interactions with the environment.

Quindío Botanical Garden director Alberto Gómez Mejía, who first proposed the plan nearly a decade ago, believes the moth poses little risk. He points to an explosion in the moth's population in the southern state of Putumayo—a hotspot for cocaine cultivation—in 1982. Caterpillars ravaged the coca crops, but soon after the food source disappeared, so did they.

"If they don’t have access to that plant, they die of hunger," he says.

But what if, in the living laboratory of the rainforest, it turns out that the caterpillar isn’t such a picky eater after all? That kind of disruption in the ecosystem could have a lasting impact. There could also be consequences for people: Indigenous peoples’ traditional uses for coca could be compromised if the moth turned out to eat other coca species. And many campesino farming families living in remote parts of the forest eke out a living growing coca alongside subsistence crops like corn and plantains.

In short, no one knows what unintended consequences an out-of-control moth population might unleash.

For Gómez, though, the environmental damage caused by coca cultivators pushing further and further into pristine ecosystems is far greater than the risk posed by either herbicides or moths. "These are zones with plants that only exist in these places, and the coca growers are destroying them," he says. "That’s much more serious than either the use of glyphosate or the release of moths."