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[BOGOTA] Colombian biologists say caterpillars could be used to destroy illegal coca crops, which are the source of cocaine.

Alberto Gómez, president of the Colombian Botanical Gardens Network, made the proposal on 31 May in a letter to Sabas Pretelt, interior minister and president of the National Narcotics Council.

Gómez and colleagues propose releasing captive-bred moths called Elorio noyesi in areas where coca is grown illegally. The moths lay their eggs on coca plants, and the caterpillars that hatch feed on and destroy their leaves, the raw material used to produce cocaine.

This approach would be better than spraying herbicides from aeroplanes and helicopters, say the researchers. Environmental and human rights groups have complained that the herbicides have also destroyed farmers' crops and affected the health of local people (see Colombian herbicide spraying under attack).

The prominent Colombian botanist Jesús Hidrobo first proposed using caterpillars to control coca more than 15 years ago but according to Gómez, Colombian laboratories were not able then to produce enough moths to make the practice worthwhile.

Now, however, there are at least five insect hatcheries in Colombia, and together they are able to produce several thousand moths. To make the researchers' idea a reality, more laboratories would need to be built near coca plantations, producing hundreds of thousands of moths that could be regularly released into the fields.

Ricardo Vargas, director of Acción Andina, a non-governmental organisation that works on policies to fight the drug trade, says that the best way to fight the cocaine problem in Colombia is not to destroy the coca plantations but to target the drugs trade and improve policies used to combat it.

The biologists' proposal would cause coca growers to use insecticides to kill the caterpillars and add to the "huge amount of chemicals used in the process to produce cocaine", says Vargas, whose organisation will next month release a book called Drug trafficking, war and anti-drugs policy.

Gómez is also concerned about the use of pesticides. Last month, the Organization of American States published a study that concluded that spraying the herbicide glyphosate on coca does not harm human health or the environment, but said spraying could harm native plant species (see Pesticide used in Colombian war on drugs 'not harmful').

This raised concerns, repeated by Gómez in his caterpillar proposal to the interior minister, that the government might approve aerial spraying of glyphosate in national parks, where coca is being planted.

"It is a very complex problem," says Vargas. "We cannot think that with such a caterpillar we have found the solution to the drug problem."

Elorio noyesi caterpillars
feed only on coca leaves

Gonzalo Andrade, a zoologist at National University of Colombia's Institute of Natural Sciences who studies moths and butterflies, says that the caterpillars would only be part of the solution, and that the manual eradication program — which involves burning or cutting down crops — should continue.

He adds that although the caterpillars feed only on coca plants and would accelerate their eradication, research is needed to see whether the method is equally effective against each of the two coca species in Colombia.

On 14 June, the UN Office on Drugs and Crime announced that the area of Colombia on which coca is grown had fallen by seven per cent to 80,000 hectares between 2003 and 2004. In Bolivia and Peru, the area increased.