Margaret Thatcher’s Secret Plan to Combat Peruvian Cocaine with British Moths

By the Editorial Team · Sunday, August 9, 2026

In the late 1980s, the British government under Margaret Thatcher funded the development of a plan to release voracious moths, Eloria noyesi, to destroy coca crops in Peru as a biological method to reduce cocaine production. Although initial trials showed the moths could devastate large coca plantations, the project was ultimately halted due to lack of support from Peruvian authorities, highlighting early attempts at environmentally targeted drug control strategies.

In the late 1980s, the British government under Prime Minister Margaret Thatcher explored a covert biological strategy aimed at curbing cocaine production in Peru. Newly released documents reveal that ministers allocated £100,000 to develop a plan involving the release of voracious moths, Eloria noyesi, to destroy coca crops used in cocaine manufacture.

The initiative, personally approved by Thatcher, centered around breeding large numbers of Eloria noyesi at Porton Down, Britain’s chemical defense research facility. These moths specifically feed on the leaves of Erythroxylum coca, the plant from which cocaine is derived. The plan envisioned transporting the moths to South America and releasing them by helicopter over suspected coca plantations operated by drug traffickers.

According to a Foreign Office briefing, swarms of Eloria noyesi had reportedly devastated around 2,000 hectares (approximately 5,000 acres) of illicit coca plants near Tarapoto, Peru, from mid-1987 to early 1988, inflicting losses estimated at more than $37 million on drug operations. This evidence underscored the moth’s potential as a biological control agent. The briefing noted that the Peruvian government had requested assistance from British scientists to develop a simple, cost-effective mass-rearing method for the insects, suitable for operation by relatively inexperienced personnel. The objective was for the pupae or adult moths to proliferate autonomously once introduced to target fields, thereby spreading naturally through coca plantations.

Officials described the approach as a localized but effective method to reduce coca yields, characterizing Eloria noyesi as a “smart bomb” due to its host specificity and limited range. Documents highlighted that the moth, indigenous to Peru, feeds exclusively on coca bushes, minimizing risks to other plant species and allowing for discreet application that could go unnoticed as a control tactic.

Cabinet Secretary Sir Robin Butler discussed the proposal with senior civil servants in late 1989 before reporting to Thatcher, who deemed the idea sufficiently promising to warrant further exploration. The initial phase advanced with government funding of up to £100,000 (equivalent to roughly £270,000 today). However, the project ultimately stalled due to insufficient political and financial backing from Peruvian authorities, preventing implementation.

Years later, in 2015, Colombia reconsidered the concept after discontinuing the use of the herbicide glyphosate for coca eradication. The Colombian government proposed deploying moths for crop destruction but never formally adopted the measure.

The British exploration of biological agents for narcotics control illustrates an unconventional approach considered during a period of intense efforts to combat international drug trafficking. While the moth plan was never operationalized, it reflects ongoing interest in environmentally targeted strategies amid the challenges of curbing illicit drug production.

This article was reported by synthesizing coverage from multiple independent news outlets to present a balanced, unbiased account. Read about our editorial standards. Spotted an error? Let us know.