Before organophosphates, before organochlorines, before carbamates, before synthetic pyrethroids… there were botanicals.
These are naturally occurring chemicals that plants produce as their own defensive mechanism against feeding insects.
Plants have had 400 million years to develop highly complex chemicals that defend against their own specific predators, and extracts from plants have been used by humans for at least 2000 years to deter or kill insect pests.
There is documentation of pyrethrum powder being used to delouse children in ancient Persia as far back as 400 BCE, and extracts from the neem tree (Azadirachta indica) were used by ancient cultures for insecticidal purposes and remain in use today.
The Egyptians, Chinese, Greeks and Romans were all aware of the insecticidal properties of certain plants.
Despite their long history, botanicals are not used as insecticides on a large scale.
Many conventional pesticides were developed from the nerve gas research done in World War I and World War II, such as DDT. This was magic at the time—it was a very, very effective compound, and that led everybody away from what was being used, which had been natural compounds like rotenone, natural pyrethrum and nicotine.
Nobody really knew about the persistence in the environment or the environmental exposure risk of DDT and the others. Now people are starting to go back and say, “What did we do before we had these?”
Insecticidal plants
The names of many insecticidal plants seem to come from a cookbook: mint, rosemary, thyme and clove, and they are proven safe for mankind and the environment.
However, all-natural does not always mean safe for all. Nicotine is poisonous in concentrated form, and ricin, another deadly poison, is also from a plant, Ricinis communis. Deadly nightshade is a weed but has that name for a reason.
(cont next month)
See this article in Tree Fruit March 2018
