Blog: The Evolution of Plant Protection Products: From WWII to Today

This week, many events have taken place to mark VE Day, the end of the Second World War in Europe, to remember those who died in action, those who served their country, and those whose lives were impacted by the war. Reflecting on this period, I became curious about the plant protection products (PPPs) available during WWII that farmers might have used to increase food production.

The Discovery and Impact of DDT

My curiosity led me to read about DDT and its significant contribution to the Allied troops during WWII. DDT (dichlorodiphenyltrichloroethane) was discovered in 1939 by Dr Paul Müller and manufactured commercially in 1943. Before DDT, pyrethrins were among the major insecticides used, extracted primarily from flowers of the genus Chrysanthemum (Pyrethrum). However, supplies were limited and insufficient to meet the demands of wartime use to control insect pests.

The availability of DDT helped Allied forces control louse-borne typhus, particularly in crowded military and civilian environments, as well as malaria and dengue fever in tropical regions. At the time, DDT was seen as a broad-spectrum insecticide with low toxicity to mammals. It was inexpensive to produce, easy to apply to large areas, and persistent, being relatively insoluble in water, so reapplication, particularly after rain, was generally not needed.

Environmental Concerns and Regulations

In the 1960s, following the widespread use of DDT to limit malaria and as an insecticide in agriculture, the environmental impacts of DDT were recognised. The Stockholm Convention on Persistent Organic Pollutants introduced a global restriction on DDT use in agriculture in 2004. Despite this, DDT is still used today as an indoor residual surface treatment in malaria-prone countries under World Health Organisation guidelines, as an affordable and effective way to control malaria where other measures are not feasible.

Evolution of Other Plant Protection Products

A darker side to the evolution of PPPs was the development of organophosphorus (OP) compounds following wartime research on nerve gases for use in chemical warfare. Many early OPs were very effective on aphids and red spider mites. More selective OPs with lower mammalian toxicity were developed in the 1950s and '60s.

In the mid-1940s, the herbicidal properties of phenoxyacetic acids were discovered. Two examples still used today are 2,4-D (2,4-Dichlorophenoxyacetic acid) and MCPA (2-Methyl-4-chlorophenoxyacetic acid) . Together with synthetic organochlorine and OP insecticides, they enabled increased home food production with a much-reduced agricultural workforce, which was a vital part of the war effort.

Reflecting on the History of PPPs

Writing this blog has reminded me of the fascinating history of PPPs, some of which have been replaced with more benign products over the 80 years since they were developed, while others are still approved for use today. It has also reminded me of the horrendous conditions that troops had to fight in and the efforts of farmers and growers to keep feeding the population during those difficult years. They certainly deserve our thanks.