The history of the pyrethroid insecticides
The pyrethroid insecticides were developed in the 1960s and '70s by a team of scientists led by Michael Elliott at Rothamsted Research, an institute that receives strategic funding from BBSRC. They identified the most active components of pyrethrum, a natural though relatively weak insecticide mixture extracted from the chrysanthemum flowers (a type of daisy), and modified the molecular structures to improve their activity against insects.
|17%||Proportion of total insecticide sales made up by pyrethroids in 2007|
|2011||The WHO recommends the use of long-lasting insecticidal mosquito nets to tackle malaria|
|US$1.4Bn||Peak in sales of synthetic pyrethroids in 2006|
Compared to natural pyrethrins, the synthetic pyrethroids are more stable in direct sunlight. They are also significantly more effective against a wider range of insects, so farmers need to apply less insecticide to their crops. This also means pyrethroids are less likely to build up to dangerous levels in the environment. Bioallethrin and tetramethrin are two examples still used today.
Today they account for around one sixth of global insecticide sales, and global annual sales of one product, deltamethrin, exceed £130M. They are also used to impregnate bed nets, which help to reduce the spread of malaria as part of the World Health Organisation's Global Malaria Programme. Because humans possess enzymes that quickly break down pyrethroid insecticides, the pyrethroids are only toxic to people in large quantities or over long periods of time.
In a total pesticide market worth more than $7Bn each year, pyrethroids make a significant contribution to the UK economy. Furthermore, because of their natural origin some pyrethrum-based products can also be used for organic food manufacture.
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