I am a fan of cinnamon buns and I have had cinnamon sticks with apple cider, but I’d never of it as a pesticide, until I was surfing the net for ways to get rid of ants. I wondered whether this was really a thing.
Insects are, of course, vital to healthy ecosystems, but they often come into conflict with human interests. Pesticides, however, often have unintended negative side effects, as is the case of DDT. So finding more benign methods of controlling insect populations has understandable value.
Cinnamon is made from the bark of cinnamon trees, and so it is perhaps more surprising that people like it, than that insects do not. The bark gets peeled off shoots and left to dry in sun, naturally curling into quills. Cinnamon comes in over a hundred wild forms found in tropical areas around the world. True cinnamon, or Ceylon Cinnamon, Cinnamomum verum (formerly Cinnamomum zeylanicum) is supposed to have the most delicate flavour and is best for desserts, but this is perhaps just marketing. Chinese Cinnamon or cassia, Cinnamomum cassia, is produced in larger quantities and commercial products often use this, or a mixture, with the Ceylon Cinnamon.
In my exterminator research, I found that Taiwanese scientists discovered that leaf oil from Cinnamomum osmophloeum, a species of cinnamon indigenous to Taiwan, was effective at killing larvae of the yellow fever mosquito Aedes aegypti. The components of this leaf oil are similar to cassia bark oil but could be a more sustainable resource.
The key ingredients are Cinnamaldehyde, Cinnamyl acetate, Eugenol, and anethole, which also contribute to the characteristic smell of cinnamon. The most effective component was Cinnamaldehyde, an oily yellow liquid that occurs in Cinnamon leaves and bark, an insecticide with low toxicity to mammals. Cinnamyl acetate, a main component of the cinnamon smell, is used in fragrances and pest control. Eugenol is the main component of clove oil, used for killing weeds and some bugs by breaking down waxy coatings. Anethole is an important component of the smell and flavour of anise and fennel, and is used as a flavouring and also as an insecticide. So when it comes to cinnamon, it does seem that one creature’s treat is another creature’s poison.
Cinnamon trees themselves, however, are susceptible to insect attacks, including the caterpillars of the Common Mime Chilasa clytia, which eats cinnamon and other members of laurel family. Evolution is an ongoing arms race. The good and not so good thing about plant-based pesticides, is that they tend to break down fairly quickly. So cinnamon may not be a cost effective solution and I don’t see cinnamon disrupting the “spice and pesticide” sector any time soon.