Pyrethrum - from ancient discovery to advanced agriculture

credit: Botanical Resources Australia

The pyrethrum story is one of a simple daisy with a rare natural property. It is the story of an ancient discovery passed down through the ages which today is the basis of an advanced agricultural industry. It is the story of high-tech agricultural techniques and subsistence farming being mutually beneficial - of developed world technologies co-existing with African traditions. And it is a story of benefits to many. Above all, it is the story of a clear, golden oil - nature's own insecticide.

The pyrethrum daisy or Tanacetum cinerariaefolium, is a remarkable plant. Packed into microscopic oil bearing glands on the surface of the seed case in the flower's head is a complex plant oil - a combination of six organic esters - which the plant has evolved over millennia to keep insects away. Pyrethrum today is grown for this natural insecticidal oil in more than 10 countries, and the total world pyrethrum market is worth half a billion US dollars. Pyrethrum is used in insecticidal preparations from the simple mosquito coil to household aerosols to sophisticated ultra low volume foggers and sprays. The natural insecticide is remarkable in that it is fast acting against insect pests, yet breaks down quickly in UV light, leaving no residue in the environment. Because of this non-persistence, pyrethrum does not enter food chains, as has been the case with some synthetic insecticides, and no real insect resistance occurs. Crucially, although pyrethrum acts as a nerve agent on insect pests, quickly knocking them down and killing them, it is relatively non-toxic to humans and warm-blooded animals.

Pyrethrum's story begins in China during the Chou Dynasty of the first century AD, when it was first noted to kill insects. Over centuries, pyrethrum was traded along the Silk Route into Europe and the dried flowers were used in powdered form to relieve the persistent insect itches of the ancient world. Pyrethrum was widely used to delouse armies from the time of Napoleon, and the flower was introduced into Kenya to produce insecticide for the allied armies around the time of WWII. The world's major pyrethrum growing area since that time has remained the East African highlands: Kenya, Tanzania and Rwanda. Here, the perennial plant which produces flowers for harvest for up to five years, thrives on fertile volcanic soils, high rainfall and ample sunshine.

Pyrethrum in East Africa is grown mainly by subsistence farmers who supplement their food crops with a cash crop of the daisies. Seedlings are hand split, hand sown and the flowers hand picked for several months of the year. Flower heads are sold to a cooperative for refining and export, but profits do flow back to the farmers. In fact, pyrethrum cash cropping is thought to sustain around three million farming families in the East African growing region, often producing enough money for families to put their children through school, and to gain some degree of economic independence. But the East African growing area has historically been plagued by fluctuating production that caused periodic world shortages of pyrethrum, followed by years of surplus. This damaged confidence in the region's ability to meet demand, and threatened the industry's long term sustainability. Ironically, it was the entry of a new and technologically advanced competitor that restored faith in the crop.

credit: Botanical Resources Australia

The Australian island state of Tasmania entered the pyrethrum story just 25 years ago, and with an emphasis on research and development, started to be a viable second source of pyrethrum. Now supplying 30% of the world market (compared to some 70% supplied by East Africa) Tasmania and pyrethrum have gone high-tech. Run by the privately owned company Botanical Resources Australia (BRA) the Tasmanian pyrethrum industry is largely mechanised. Sowing, cutting, harvesting, extraction and refining are all performed by state-of-the-art equipment. Contract farmers, who also grow crops of beans, peas, potatoes, pharmaceutical poppies and prime beef, can learn at harvesting, with the help of GPS systems, exactly how to treat each square metre of their fields the following year for optimal yields. Extensive laboratory testing, electronic bar codes on each harvest load and a computer controlled, carbon-dioxide based refinery which can be operated online make Tasmanian pyrethrum a cutting edge, technology driven industry. Importantly, the entry of Tasmania onto the world market has stabilised supply and increased faith in pyrethrum, benefiting both major suppliers and the industry as a whole.

Pyrethrum has been exciting substantial interest around the world as environmental awareness grows. Fast acting and broad spectrum, the insecticide is relatively safe to use everywhere from homes to broad-scale spraying operations. It is one of the few insecticides approved for use on organic farms in Europe, the US and Australia. And pyrethrum also benefits many - from the subsistence farmer in Africa growing pyrethrum as a cash crop, to families worldwide burning pyrethrum mosquito coils to avoid malaria, and the hobby gardener spraying his vegetables in rural England - determined that next time, the bugs won't get his crop.

Article by Gabi Mocatta, Botanical Resources Australia