Researchers rediscover fast-acting insecticide used by Nazi army, lost after war

DFDT was dismissed by US military officials following World War II in favor of DDT, but could be used to combat malaria and other mosquito-borne illnesses

Luke Tress is an editor and a reporter in New York for The Times of Israel.

New Zealand military personnel protect themselves from mosquitoes while receiving US military training on the Pacific island of Espiritu Santo, April 23, 1944. (US Navy via AP)
New Zealand military personnel protect themselves from mosquitoes while receiving US military training on the Pacific island of Espiritu Santo, April 23, 1944. (US Navy via AP)

Researchers from New York University have uncovered a fast-acting insecticide with an unsettling history.

The chemical, DFDT, could have an impact combating disease-carrying mosquitoes while causing less environmental damage than the chemically similar DDT.

American scientists previously looked into the insecticide in the 1940s, but it was lost in the chaos following World War II, likely due to its ties to the Nazi regime.

“We set out to study the growth of crystals in a little-known insecticide and uncovered its surprising history, including the impact of World War II on the choice of DDT — and not DFDT — as a primary insecticide in the 20th century,” Bart Kahr, professor of chemistry at New York University, said in a statement published by the university.

The findings were published Friday in the Journal of the American Chemical Society.

The chemistry researchers had been examining the insecticide DDT, known for its devastating environmental effects. They made some changes to DDT’s crystal structure by swapping out chlorine atoms for fluorine, and tested the new chemical, known as DFDT, on fruit flies and mosquitoes.

DFDT killed mosquitoes — including species that carry malaria, yellow fever, Dengue and Zika — two to four times faster than DDT.

“Speed thwarts the development of resistance,” said study author Michael Ward. “Insecticide crystals kill mosquitoes when they are absorbed through the pads of their feet. Effective compounds kill insects quickly, possibly before they are able to reproduce.”

The researchers then wanted to know if their chemical creation, DFDT, had been used in the past — and uncovered its dark history.

Poring through historical documents, they found that German scientists had created DFDT for use as an insecticide in World War II, and Nazi military forces used it for insect control in the Soviet Union and North Africa.

Meanwhile, the US military was using DDT for the same purpose in Europe and the Pacific theater.

Malaria and other tropical diseases ravaged US forces in the Pacific and elsewhere during the war.

US soldiers suffering from malaria recover in a field treatment center in Guadalcanal during World War II, 1943. (AP)

After the war, the use of DFDT was abruptly put to an end, as Allied officials who interviewed Nazi scientists disregarded their claims that DFDT killed bugs faster and was less toxic to animals than the US-produced DDT.

A declassified military report cited by the researchers, which referred to DFDT as “Gix” or “Fluorgesarol” and by its chemical structure, reads: “The German claims as to the superior insecticidal action of their [DFDT], in comparison to DDT, are not clearly supported by their meager and inadequate tests against houseflies. Moreover, the Germans who tested it differ sharply among themselves as to their conclusions.”

The Swiss chemist Paul Müller, who discovered DDT’s use as an insecticide in 1939 and won a Nobel Prize for his work with the chemical in 1948, notably said in his acceptance speech that DFDT was a faster killer and should replace DDT in the future.

The chemical was mostly forgotten, though. The entomologists the NYU researchers consulted with had never heard of it.

“We were surprised to discover that at the outset DDT had a competitor which lost the race because of geopolitical and economic circumstances, not to mention its connection to the German military, and not necessarily because of scientific considerations. A faster, less persistent insecticide, as is DFDT, might have changed the course of the 20th century,” Kahr said.

The lost chemical is more than a historical anecdote — malaria kills a child every two minutes, according to the World Health Organization. New mosquito-borne diseases can crop up, such as the Zika virus, which spread terror in South and Central America in a 2015-2016 epidemic, and with global warming, mosquitoes’ ranges are increasing.

Mosquitoes are also increasingly resistant to control measures, the NYU researchers said.

“While more research is needed to better understand the safety and environmental impact of DFDT, we, along with the World Health Organization, recognize the urgent need for new, fast insecticides. Not only are fast-acting insecticides critical for fighting the development of resistance, but less insecticide can be used, potentially reducing its environmental impact,” said Ward.

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