Could cocaine-eating caterpillars replace herbicides in Colombia?

Colombia may recruit an unlikely ally in the fight to curb cocaine production: hungry caterpillars.

Stopping cocaine production at the source has been a problem the Colombian government has wrestled with for decades. For an issue that touches not only human and ecological health, but also political negotiations with rebel groups that guard and profit off some of the crops, a solution that pleases everyone has been understandably elusive.

Until now, that is.

Colombian President Juan Manuel Santos announced on Saturday that he is ending the use of a controversial herbicide the country has been using to wipe out cocaine-producing plants in the country. Mr. Santos said the herbicide, glyphosate, will be replaced by "manual" alternatives to coca plant eradication, including the controlled release of a special breed of moth that eats the plants.

Santos added that he was making his decision based on a recent World Health Organization decision to classify glyphosate as a carcinogen. A report from the International Agency for Research on Cancer, the specialized cancer research arm of the agency, released in March said that the herbicide is "probably carcinogenic to humans."

The conclusion provoked some criticism when it was released. The European Union's Glyphosate Task Force has said that the herbicide "poses no unacceptable risk to humans, animals or the environment," and the German Federal Institute for Risk Assessment declared it non-carcinogenic in 2014.

Robb Fraley, Monsanto's chief technology expert, called the IARC report a "clear example of agenda-driven bias."

“We are outraged with this assessment,” said Mr. Fraley, according to Capital Press.

Glyphosate is one of the most popular herbicides in the world, and is a key ingredient in Monsanto's popular Roundup weed killer. According to Reuters, more than 280 million pounds of glyphosate were used in US agriculture in 2012, the most recent year with available data, an increase from 110 million pounds in 2002.

The use of glyphosate to destroy coca plants in Colombia was a US-funded and operated initiative in place since the early 2000s. The spraying program – which covered 136,000 acres last year and over 4 million acres of land in Colombia since it began – is partly carried out by US contractors. Kevin Whitaker, the US ambassador to Colombia, said a decision on whether to use the chemical is a decision for Colombia and the US government respects it, according to the Associated Press.

The main alternative to glyphosate could be a special breed of moth native to the region that feeds on the cocaine-producing plants. The beige-colored Eloria noyesi moths lay their eggs on the leaves and, when they hatch about a week later, caterpillars emerge and devour the leaves.

The moth solution has been proposed before, but met opposition in 2005 because experts were worried about the butterflies causing "ecological mischief."

The idea originally was proposed by Alberto Gomez Mejia, president of the privately funded National Network of Botanical Gardens. The plan, which is being reexamined in light of the decision to cease aerial fumigation, would have bred thousands of the moths in laboratories, then released them in coca-growing areas. Each moth could lay more than 100 eggs in a month, but the plan was criticized at the time because such a concentrated release could threaten other plants besides the coca species.

"With a plan like this, the chance for ecological mischief is very high and very dangerous," said Ricardo Vargas, director of the Colombian environmental group Andean Action, in a 2005 interview with the AP.

The suspension of aerial fumigation could have the positive side-effect of helping government negotiations with the country's main rebel group, the Revolutionary Armed Forces of Colombia (FARC).

Airborne fumigation was introduced in Colombia in large part because guerrilla fighters protecting coca crops made manual, on-the-ground eradication dangerous.

The two sides had already agreed that aerial fumigation only be used as a last resort, and FARC has demanded that an end to the spraying must be part of any peace deal in the 50-year war.

"If a successful peace process demobilizes Colombia’s guerrilla groups, the main justification for fumigation disappears," said the Washington Office on Latin America.