Since their original cultivation in ancient China, chrysanthemums have been planted as attractive, brightly colored and gently scented additions to home and public gardens.  Yet besides planting them for their visual and olfactory appeal, early cultivators of the plant also noted that areas of gardens where chrysanthemums flourished often had less insects.

History of the Pyrethrum Daisy

Particularly the chrysanthemum known as the "pyrethrum daisy" or Tanacetum cinerariaefolium demonstrates a remarkable ability to drive away biting insects.  The Chinese traded this special chrysanthemum in dried form along the Silk Route and into Europe where it became popular as a lice and flea repellent.  By the 1800s crushed pyrethrum flowers were a commonly found ingredient in European pharmacies.

According to an article published in the November 2003 New Agriculturist, Napoleon used the pyrethrum daisy to delouse troops, and later, the flower was introduced as a crop plant in Kenya specifically to be used as a repellent for WWII allied forces.  In 1946, in Amsterdam, pyrethrum was added to the municipal water supply.  Not only did the pyrethrum succeed as an insecticide, but people continued to drink, bathe and cook with the water without becoming ill. 

Pyrethrum Formulations

The pyrethrum flower evolved this natural ability to avert insects as a defense mechanism against hungry caterpillars and other plant-eating insects.  The oil responsible for the repellent is located on the surface of closely packed seed cases located in the yellow center of the flower head.  To extract it, the flowers are first dried, pelletized, then dissolved and refined. 

Not until the last few decades, however, have scientific breakthroughs allowed us to create a powerful and natural insecticide from the plant that could be safely used as a residential spray to control backyard mosquito populations. The problem with using pyrethrum exact by itself is that mosquitoes will often recover after a few minutes. Current formulations of pyrethrum sprays such as the InsectAway^TM used by Total Mosquito Control include a synergist which prevents the insects from metabolizing the pyrethrum and ensuring that the "knockdown power" of the insecticide is permanent.  

Pyrethrum Safety

Pyrethrum is extremely safe when used as directed.  According the National Pesticide Telecommunications Network (NPTN) Fact Sheet, pyrethrins (the active ingredient in pyrethrum) are "one of the least poisonous insecticides to mammals." 

Pyrethrum is used safely on delicate grape vines and in organic farming.

Natural pyrethrins are commonly used in:

•  indoor bug bombs
•  pet flea sprays and tick dips
•  human head-lice treatments
•  termite treatments
•  restaurant foggers
• on garden plants
• to combat locusts
• as food crop insecticides. 

And pyrethrum is one of the few pesticides approved for use in organic farming in Europe, the US and Australia.  Wine makers are especially fond of pyrethrum for their grape crops as it decomposes quickly in the environment, within a period of only a few days, and leaves no residue.

Pyrethrum Today

Kenya produces 70% of the world's Pyrethrum crop.

The last two and a half decades have seen a growing demand for pyrethrum supplies and have spurred a new source for pyrethrum production.  Once almost the sole harvester of the pyrethrum daisy as a cash crop, Kenya has a new competitor, the Australian island of Tasmania.  Australian pyrethrum production now accounts for 30% of the world market and has stabilized the market considerably. 

As pyrethrum can be sown only twice in the year, Kenyan farmers have a short window in which to decide which cash crop to plant.  Before, fluctuations in Kenyan farmers' crop selections rollercoasted international pyrethrum prices.  Yet now a second world source has given the pyrethrum industry somewhere to turn.

An ancient Chinese proverb intones, "If you would be happy for a lifetime, grow chrysanthemums."  As we learn more about the benefits of this special chrysanthemum, we can't help but wonder if there is more to the old saying than meets the eye.