Paper short abstract:

This paper evaluates the importance of pyrethrum-based insecticides as a means of tackling insect-borne diseases in the Japanese military (1900s-1945) and explains why pyrethrum was a relatively insignificant wartime material in Japan, in contrast to its high importance for the US and UK armies.

Paper long abstract:

Conventional accounts of insect control during WWII focus almost entirely on the synthetic insecticide DDT and narratives that celebrate its unparalleled efficacy. The fame of DDT has obscured the fact that the nations fighting in WWII actually deployed a range of substances to tackle the vectors of insect-borne diseases. One such substance was the natural insecticide pyrethrum, produced from the dried and ground flowers of a daisy-like plant Chrysanthemum cinerariifolium. While historians including Edmund Russell and Sabine Clarke have argued that pyrethrum was highly significant for the Allies’ insect control efforts, there is still an unresolved question about Japan: were the Japanese armed forces big consumers of pyrethrum? Given that Japan was the world’s largest producer and exporter of dried pyrethrum flowers at the time, it would seem natural to suggest that pyrethrum played a similarly important role for the Japanese military both during and before WWII – which, I will argue, was not the case.

I will start with tracing the history of the use of pyrethrum by the Japanese military (1900s-late 1930s) against the background of other ways to control the spread of insect-borne diseases. Pyrethrum took a variety of forms and functions, including: a powder that protected the soldiers against flies and lice during the Russo-Japanese War; a component of sprays and wipes applied by Japanese military veterinarians to tackle horse pests; an active compound of coils that Japanese military stationed in Taiwan used to repel malaria mosquitoes. By locating pyrethrum within the wider set of measures against insect-borne diseases, I will show that pyrethrum was one of many available tools of disease control, but its importance was never paramount.

I will then attempt to explain why, in contrast to the US and UK militaries, pyrethrum was relatively insignificant to the Japanese armed forces during WWII. This explanation is necessary because the Japanese army suffered heavy losses from malaria. One of the factors that prevented the large-scale use of pyrethrum by Japanese soldiers was the acuteness of food shortages, which led to the prioritization of growing food crops over industrial ones such as pyrethrum.